essay about vitamin c

Importance of Vitamin C for the Human Body Essay (Article)

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The importance of Vitamin C

Vitamin c in the diet, disease prevention, the nutritional value of vitamin c, sources of vitamin c, daily requirement of vitamin c, when we lack vitamin c.

Vitamin C is also known as the ascorbic acid and is a necessary nutrient for people and other animals. It is among the most essential vitamins for the human health. The nutrient is soluble in water and is not stored in the body of human beings. Vitamin C is an antioxidant which assists in body protection against pollution. It also promotes the development of healthy cells, normal tissues and repairs injuries as well as helping in the absorption of calcium (Institute of Medicine, 1997).

The major function of ascorbic acid is that it assists in synthesizing collagen. This is an essential component of blood vessel, bones and ligaments. Ascorbic acid is also essential for the development of healthy gums and assists in safeguarding against infection. Since it is excreted from our bodies regularly, it becomes very important to supply it at the same rate.

Any diet without vitamin C should be considered incomplete as the nutrient serves to prevent a number of diseases and enhance the immune system. These factors are pertinent to the roles played by other nutrients in our bodies. The vitamin can be taken with or without other foods and can be available in supplement form.

In your diet, vitamin C remains the core nutrient to facilitate quick absorption of other nutrients. As noted earlier, ascorbic acid is soluble in water and thus acts as the medium through which some of the insoluble elements with nutritional value can be absorbed in our bodies. In addition, the availability of vitamin C makes it a substitute to other rare vitamins which enhance the same functions in our bodies. Therefore, it enriches the diet through various mechanical and nutritional functions that other vitamins cannot support.

In prevention of the many diseases related to nutrition, Vitamin C is paramount as the nutrient has served protective role predominantly. In the old days, ascorbic acid was referred to as ‘antiscorbutic factor’ as it assisted in the prevention of scurvy (Carpenter, 1988). In those days when the disease was discovered, vitamin C obtained from lime prevented the gums and skins of sailors from swelling. Even today, ascorbic acid has been the only nutrient that prevents the disease from affecting us.

Moreover, the role of disease prevention played by ascorbic acid extends beyond the gums and skin. The optimal intake of the nutrient is associated with the prevention of cancer, heart diseases, joint ailments and cataracts (El-Sokkary & Awadalla, 2011). The nutrient attains its protective outcome by working as an antioxidant and safeguarding our cells from any damage based on oxygen. Structures of our tissues that contain fat are especially reliant on ascorbic acid for protection.

These arguments suggest that the nutritional value of ascorbic acid is the development of a healthy body. The nutrient enhances body systems such as the immune system, blood system and the digestion process. Another nutritional value of ascorbic acid is the significant interactions it has with a number of essential minerals in our bodies (Institute of Medicine, 1997). Optimal intake of the nutrient can influence copper metabolism in our bodies.

The nutrient can substantially enhance metabolism and the absorption of iron, even at small amounts. Ascorbic acid also has significant interaction with other vitamins. While vitamin A is less toxic in the presence of ascorbic acid, vitamin E has been identified to work better with vitamin C in its antioxidant effect. Ascorbic acid is the only vitamin that interacts with both the vitamins and minerals for the benefit of our bodies. Interactions of other vitamins with minerals have been associated with toxicity of the human body.

The major sources of vitamin C are the citrus fruits such as orange, lemon and grape fruit (Fediuk, 2000). Other fruits containing the nutrient are mangoes, kiwi fruit, papaya, strawberries, pineapple, watermelon, blueberries and raspberries. Vegetables are also good sources of the vitamin and include green and red pepper, sweet and white potato, winter squash, cauliflower, broccoli, Brussels sprouts, spinach, turnip greens and cabbage.

Some cereals are also reinforced with vitamin C. However, ascorbic acid can be destroyed easily when preparing, storing and cooking food. The preservation of the nutrient requires the following of some precautions. The fruits and vegetable would serve better if taken in their raw forms. Boiling, steaming or simmering foods in water for a long time can destroy the nutrient.

Prepared fruit juices should not be refrigerated for more than two days. Other sources such as potatoes should be cooked without peeling off the skin. Any fruit or vegetable should not be soaked in water as ascorbic acid is very soluble in water.

The recommended daily intake of vitamin C for a normal healthy person is 90 milligrams. However, this intake is influenced by other factors such as age, gender and lifestyle. In addition, pregnancy and ailments are also significant factors that can determine the amount of ascorbic acid an individual can take. However, the best way of getting daily requirements of important nutrients including ascorbic acid is to ensure that you take a balanced diet that involves a variety of products. The dietary reference intake for the nutrient is as follows:

It is also recommended that individuals who smoke and at any age should take higher amounts of vitamin C approximately by an additional 35 milligrams daily. Moreover, pregnant women or nursing mothers should take the vitamin in higher amounts. While individuals in these categories should take optimal amount of the vitamin to prevent diseases, a balanced diet should provide enough amount of the nutrient for a normal person to be free from diseases.

When we lack vitamin C, the synthesized collagen becomes too unstable to do its functions and hence risk getting scurvy. This disease is characterized by spongy gums, loose teeth, pale skin, poor healing and bleeding from nose membranes. Other effects include swollen and painful joints, dry and splitting hair, coarse and dry skin.

The symptoms of ascorbic acid deficiency are fatigue, weight loss, powerlessness, weakness and gloominess. Very low levels of the nutrient may result into hypertension, gall bladder ailments, cancer, atherosclerosis and stroke (Kurl et al, 2002). Therefore, high levels of the nutrient could be required when one has a fever or infection.

Carpenter, K. J. (1988). The History of Scurvy and Vitamin C . London, UK: Cambridge University Press.

El-Sokkary, G. H. & Awadalla, E. A. (2011). The protective role of vitamin C against cerebral and pulmonary damage induced by Cadmium Chloride in male adult albino rat. The Open Neuroendocrinology Journal , 4(1), 1-8.

Fediuk, K. (2000). Vitamin C in the Inuit diet: past and present . Web.

Institute of Medicine (U.S.) Committee on International Nutrition–Vitamin C in Food Aid Commodities. (1997). Vitamin C Fortification of Food Aid Commodities: Final Report . New York, NY: National Academies Press.

Kurl S. et al. (2002). Plasma vitamin C modifies the association between hypertension and risk of stroke. Stroke , 33(6), 1568-73.

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The Health Benefits of Vitamin C

May reduce inflammation, strengthen the immune system, and support brain health

Verywell / Anastasia Tretiak

What Is Vitamin C?

• Benefits and Uses
• Side Effects

Precautions

Interactions.

Vitamin C is touted for its many health benefits: It boosts immunity, improves heart health, bolsters iron absorption, and much more.

Vitamin C is an essential nutrient needed for tissue growth, development, and repair. An antioxidant, it helps protect cells from free radicals—unstable molecules that damage cells.

The body cannot produce vitamin C and must get it through diet or supplements. Vitamin C–rich foods include citrus fruits, berries, broccoli, cabbage, peppers, potatoes, and tomatoes. Vitamin C supplements are available as capsules, chewable tablets, and powder that is added to water.

This article discusses vitamin C benefits, uses, and sources. It also explains the symptoms of vitamin C deficiency, possible side effects, precautions, and interactions.

Dietary supplements are not regulated in the United States. The U.S. Food and Drug Administration (FDA) does not test products for safety and effectiveness. Quality control testing is often done by a third party, such as USP (United States Pharmacopeia), Consumer Labs, or NSF International. This helps ensure the supplements contain the ingredients on the label.

However, third-party testing does not mean the supplement is effective or safe for everyone. Before taking any supplements, talk to your healthcare provider. Some supplements have negative interactions with medications or other supplements.

Supplement Facts

• Active ingredient : Vitamin C, ascorbic acid
• Alternate names : Ascorbic acid, dehydroascorbic acid
• Suggested dose : Recommended dietary allowance ranges from 75 to 90 milligrams (mg) per day for adults
• Maximum dose : Adults should not exceed 2,000 mg a day
• Safety considerations : Generally safe if taken as recommended

Vitamin C, or L-ascorbic acid, is an essential nutrient. That means your body doesn't make it, so you have to get it through diet or supplements. Vitamin C is in many foods, such as oranges , red and green peppers, and kiwi .

Research shows vitamin C has many general health benefits. However, the science is inconclusive when it comes to using vitamin C to treat or prevent specific health conditions.

Vitamin C Benefits and Uses

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent any disease.

Vitamin C has been marketed for use to treat and/or prevent many conditions, from the common cold and COVID-19 to arthritis and Alzheimer's disease . Even so, there's scant evidence to support most claims about vitamin C.

What researchers have learned is that vitamin C appears to play a lot of important roles in your body. The most beneficial aspect may be its antioxidant activity.

Get Medical Advice

Supplement use should be tailored to your specific health issues and needs. Before starting a supplement, talk to a qualified healthcare provider, such as a Registered Dietitian or pharmacist.

May Lower Risk of Chronic Illnesses

Vitamin C is an antioxidant, meaning it's one of many natural substances that may help treat, slow, or prevent some health problems. It does this by neutralizing free radicals , which are unstable molecules that can damage cells and cause disease.

When you have a lot of free radicals in your system, it can cause a condition called oxidative stress . Research has linked many chronic diseases to oxidative stress, including heart disease, rheumatoid arthritis, chronic obstructive pulmonary disease (COPD), and kidney disease.

Preventing or reducing oxidative stress may help stave off health problems by:

• Boosting your immune system
• Lowering inflammation
• Keeping your cells healthy

However, research into using antioxidants to treat or prevent specific conditions has been a mixed bag.

Free radicals come in many types; some are harder for antioxidants to scavenge. Their location in your body can also make a difference, as certain environments (e.g., inside a cell versus in fluids outside the cell) can make the antioxidant activity more or less successful.

Moreover, researchers say it's important to be "realistic about where, when and to what extent oxidative stress is part of a disease." So, as they learn more about the disease processes and the role of oxidative stress, researchers may find roles for antioxidants like vitamin C.

In the meantime, while they're generally considered good for your health, don't expect vitamin C or any other antioxidants to take the place of other treatments.

What Causes Free Radicals?

Molecules in your body become free radicals when they're exposed to things like environmental pollutants, cigarette smoking, and chronic inflammation.

Lowers Heart Disease Risk

Oxidative stress is believed to play a role in the development of some cardiovascular diseases ("cardio" means heart, "vascular" refers to blood vessels).

A major reason for this is that oxidative stress can trigger atherosclerosis , which is the thickening or hardening of arteries due to plaque buildup from cholesterol , fat, and other substances. This can lead to coronary artery disease .

Studies have also suggested that oxidative stress may play some role in:

• Ischemia (impaired blood flow)
• Hypertension (high blood pressure)
• Cardiomyopathy (conditions of the heart muscle)
• Cardiac hypertrophy (enlargement and thickening of the heart muscle)
• Congestive heart failure (impaired pumping ability)

Even so, research into vitamin C for treating and preventing heart disease has mostly found no effect.

One promising bit of information came out in a 2020 study. It showed that vitamin C supplements helped lower blood pressure in people with hypertension. Hypertension , especially when combined with atherosclerosis, is a risk factor for heart disease.

May Help Reduce Risk of Certain Cancers

A lot of research has investigated the role of antioxidants, including vitamin C, in cancer care and prevention. However, the results have yielded inconsistent results.

Most studies have found that vitamin C supplementation, either on its own or in combination with other supplements, cannot prevent or treat cancer.

Some studies have shown that when used in supportive care, high-dose intravenous (IV) vitamin C can improve quality of life and reduce the side effects of standard cancer treatments. However, studies have also shown that antioxidants can have a downside. They may:

• Help cancerous or pre-cancerous cells survive
• Possibly make some cancer treatments less effective

Some healthcare providers recommend eating more antioxidant-containing fruits and vegetables, as people with diets rich in vitamin C may have a lower risk of getting certain types of cancer. However, it's important to remember that no one food will prevent cancer.

Moreover, vitamin C supplements themselves do not appear to prevent cancer. Eating a well-balanced diet in general, including antioxidants, is beneficial for your overall health.

Future studies are needed to establish the role of antioxidants like vitamin C in cancer. Talk to your oncologist before starting any supplements during cancer treatment .

Can Prevent Gout Attacks

Gout is a common and extremely painful type of arthritis that mainly affects the big toes. It's caused by excess uric acid (a waste product) in the blood, which causes crystals to form in the joints. The crystals then cause inflammation, which leads to painful attacks.

Several studies have shown that vitamin C can prevent gout by lowering levels of uric acid in the blood. This may, at least in part, be due to its antioxidant activity. Uric acid levels appear to be higher in people with significant oxidative stress.

However, a 2021 review of studies concluded that, while results have been promising, more high-quality studies on humans need to be done to say for sure that it's a safe and effective treatment or preventive measure.

Prevents Iron-Deficiency Anemia

With anemia , your blood doesn't contain enough red blood cells, which carry oxygen from your lungs to your body's tissues. The most common type of anemia involves a deficiency of iron , which your body needs to make red blood cells.

Vitamin C is known to help your body absorb some nutrients. Among healthcare providers, that led to a long-standing practice of recommending vitamin C supplements with iron supplements for treating anemia.

A 2019 article found that vitamin C increased iron absorption by 67%. A 2020 study casts doubt on that, though. It found that iron supplements alone improved anemia just as much as iron plus vitamin C.

The different results may be related to what kind of iron people took. Nonheme iron from plant sources is better absorbed with vitamin C. Heme iron, the form found in meat, is better absorbed in general because it has higher bioavailability than nonheme iron. More research is needed to sort this out.

Boosts Immunity and Speeds Healing

Vitamin C's best-known use is for boosting the immune system. It does this by:

• Helping your body make several types of specialized immune cells that guard against infection
• Improving the function of those immune cells
• Protecting them from damage by free radicals

Studies show vitamin C's effect on the immune system may help with certain infections, such as:

• Sepsis (an extreme, life-threatening response to infection)
• Other respiratory infections

Vitamin C is also sometimes used orally (by mouth) or topically (applied to the skin) for skin healing. According to research, vitamin C use may:

• Reduce deaths from severe burns (in high oral or IV doses soon after admission to a hospital)
• Promote wound healing (orally or topically)
• Reduce skin inflammation in conditions such as psoriasis and atopic dermatitis (orally or topically)
• Protect skin against damage from the sun (orally or along with topical vitamin E)

These abilities are believed to be largely due to vitamin C's antioxidant activity along with its ability to promote collagen production in the skin.

This is likely better achieved with nutritional intake (including supplements) rather than topically because collagen is present in deeper layers of skin and can't penetrate the outer layers to get there.

What Is Collagen?

Collagen is a protein in your body that makes tissues strong, resilient, and able to tolerate stretching. It's in skin, bones, muscles, tendons, and cartilage.

Fights the Common Cold

Traditional wisdom about taking vitamin C for the common cold may not be as wise as you think. Research has provided mixed evidence about vitamin C for treating or preventing these respiratory infections.

Several studies, including a large systematic review of the evidence, suggest vitamin C supplements:

• May shorten the duration of the common cold
• May reduce the severity of cold symptoms
• May reduce the likelihood of colds in people in extreme environments (e.g., soldiers, endurance athletes)

Even these points aren't firmly conclusive, though, and some studies have found vitamin C may only have a minimal or no effect on how long your cold lasts.

More research needs to be done before researchers can draw any firm conclusions.

Slows Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is an eye disorder that can, over time, cause blindness. Research on whether vitamin C and other antioxidants can prevent AMD has been inconclusive. But some research suggests it may slow it down.

The Age-Related Eye Disease Study (AREDS), a large clinical trial, included almost 3,600 older adults with AMD. The participants were divided into four groups and given different treatments:

• Group 1: Antioxidant supplements: vitamin C, beta carotene, vitamin E
• Group 2: Zinc , copper
• Group 3: Antioxidants plus zinc
• Group 4: Placebo

After six years, the participants who got supplements had less AMD progression. However, researchers can't be sure that vitamin C itself made a difference.

This is an older study, though, and since then, a number of other studies have failed to show that vitamin C alone is helpful against AMD. However, a 2023 Cochrane review found vitamin C, taken alone with vitamin E, beta‐carotene, and zinc, probably slows down progression to late AMD.

Protects Brain Health

Vitamin C's antioxidant activity may play a role in brain health.

Research suggests regular dietary intake plus supplements may protect you from neurodegeneration related to aging and diseases such as:

• Alzheimer's disease
• Parkinson's disease
• Multiple sclerosis
• Amyotrophic lateral sclerosis (ALS)
• Huntington's disease

Vitamin C may even help treat or lower your risk of mental health disorders, including:

• Schizophrenia

Studies suggest vitamin C deficiency may contribute to the development of these mental and neurodegenerative conditions and that supplementation may help alleviate symptoms. However, this work is preliminary, and more research is needed.

Vitamin C Deficiency

Vitamin C deficiency is rare in developed countries. In the United States, only about 8.4% of the population is believed to be vitamin C deficient.

You'd have to get less than 10 milligrams (mg) per day from food for about a month to feel the effects of a vitamin C deficiency. In severe cases, this can lead to scurvy (which is rare in the U.S.).

Symptoms of scurvy include:

• Bleeding gums

Vitamin C deficiency is treated with vitamin C supplements. Some symptoms improve within the first 24 hours of treatment. Others may take a few weeks or months to resolve.

What Causes a Vitamin C Deficiency?

A deficiency occurs either from insufficient nutrient intake in the diet or increased losses due to poor absorption.

People who don't consume various foods, mainly fruits and vegetables, are at greater risk of vitamin C deficiency. Smokers have a higher requirement for vitamin C, so smoking may also be a risk factor.

Additionally, people with malabsorption disorders may become deficient because they can't absorb enough vitamin C.

How Do I Know if I Have a Vitamin C Deficiency?

Symptoms of a vitamin C deficiency include:

• Gingivitis (gum disease)
• Petechiae (small red spots on the skin)
• Poor wound healing

If you have these symptoms and know your vitamin C intake is low, or if you rarely eat fruits and vegetables, talk with your healthcare provider about whether supplements are right for you.

What Are the Side Effects of Vitamin C?

Vitamin C is generally considered safe, but high doses can cause side effects. These may include:

• Stomach cramps
• Kidney stones

Higher doses are more likely to lead to side effects. Doses over 2,000 milligrams a day may increase the risk of diarrhea and kidney stones. If you have a history of kidney stones, taking more than 1,000 milligrams a day may increase your chances of having more.

Vitamin C supplements are not right for everyone. Talk to your healthcare provider first if you are experiencing any of the following:

• Undergoing cancer treatment : Vitamin C supplements can interact with some cancer therapies .
• Chronic kidney disease : Vitamin C can increase oxalate formation and lead to kidney failure.
• G6PD : Large amounts of vitamin C (administered intravenously) have caused hemolysis (the breakdown of red blood cells) in people with a metabolic disorder called glucose-6-phosphate dehydrogenase (or G6PD). However, this is uncommon.
• Iron overload : Vitamin C supplementation can exacerbate symptoms since it has a role in iron absorption.

Dosage: How Much Vitamin C Should I Get?

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.

For most healthy people, it is easy to get adequate amounts of vitamin C through food. You can meet your recommended dietary allowance (RDA) for vitamin C each day by eating just one of the following:

• Red bell pepper
• Cup of tomato juice
• Cup of strawberries

The RDA for vitamin C is as follows:

There are two important caveats to these recommendations:

• If you smoke, take an additional 35 milligrams per day.
• If you've been diagnosed with a vitamin C deficiency, you'll need between 100 and 200 milligrams per day until a blood test shows normal levels.

Taking high doses may be appropriate for some people, but it usually provides no extra benefit. Your body controls how much vitamin C it absorbs.

That means it'll take what it needs from food and supplements, and anything beyond that comes out in your urine. Taking 1,000 milligrams a day or more actually drops your absorption rate by about 50%.

Upper Limits

The tolerable upper intake level (TUL) is the highest amount you can safely take. Doses beyond that are more likely to cause side effects.

For vitamin C, the daily TUL is different for different groups:

Adults : 2,000 milligrams

• 1 to 3 years: Less than 400 milligrams
• 4 to 8 years: Less than 650 milligrams
• 9 to 13 years: Less than 1,200 milligrams
• 14 to 18 years: Less than 1,800 milligrams

Pregnant people : 2,000 milligrams for adults or less than 1,800 milligrams for teens

What Happens if I Take Too Much Vitamin C?

Excessive amounts of vitamin C (above TUL) can result in:

If you're healthy, taking recommended levels of vitamin C supplements generally doesn't pose risks.

If you take estrogen or estrogen-based contraceptives , vitamin C may increase the risk of hormonal side effects . This is because vitamin C may slow the rate at which estrogen leaves your body.

Vitamin C can also increase the absorption of certain drugs, such as:

• Aluminum from antacids: Do not take vitamin C and antacids at the same time. Wait at least two hours after taking vitamin C before taking an antacid. Wait four hours after taking an antacid to take vitamin C.
• Levothyroxine, a thyroid hormone treatment

Vitamin C supplementation can make some medications less effective, including:

• The antipsychotic drug fluphenazine
• Certain HIV medications, such as indinavir
• Certain chemotherapy drugs

This is not a complete list of interactions that may occur with vitamin C. Talk to your healthcare provider and pharmacist before starting vitamin C supplementation or adjusting your intake and let them know about everything you're taking; this includes prescription and over-the-counter drugs, vitamins, and herbal supplements.

How to Store Vitamin C

Store vitamin C supplements in a closed container, away from exposure to light.

Sources of Vitamin C and What to Look For

Vitamin C is readily available in your diet, and most people can get the required amounts from food.

Multiple vitamin C supplement formulations are readily available. You can buy them from most stores and websites that sell nutritional supplements.

Food Sources of Vitamin C

It is always best to get your nutrients from food rather than supplements.

Fruits and vegetables, especially citrus fruits, are good sources. Foods naturally rich in vitamin C include:

• Raw red bell peppers : 95 milligrams per 1/2-cup serving
• Orange juice : 93 milligrams per 3/4-cup serving
• Orange : 70 milligrams per one medium fruit
• Kiwi : 64 milligrams per one medium fruit
• Raw green peppers : 60 milligrams per 1/2-cup serving
• Cooked broccoli : 51 milligrams per 1/2-cup serving
• Strawberries : 49 milligrams per 1/2-cup serving
• Cooked Brussels sprouts : 48 milligrams per 1/2-cup serving
• Tomato juice : 33 milligrams per 3/4-cup serving
• Cantaloupe : 29 milligrams per 1/2-cup serving

If you don't get enough vitamin C from what you eat, a supplement can help get you to the right levels.

Vitamin C Supplements

Vitamin C supplements are available as a single nutrient supplement or combination supplement. You can find them in many forms, such as:

• Chewable tablets
• Dissolving powders and tablets

You may also see different types of vitamin C, including:

• L-ascorbic acid : Typically derived from corn
• Combination supplements : Common ingredients are sodium or calcium
• Citrus bioflavonoids : Compounds from fruits such as oranges, grapefruits, and tangerines
• Rose hips : A type of wild plant sometimes used in medicinal compounds
• Acerola powder : The fruit acerola has a high ascorbic acid content
• Camu camu : A type of berry that grows on shrubs in the Amazon rainforests

No one form is more effective than another. Remember to look at the dosages and avoid exceeding the TUL.

Also, pay attention to units of measure. The RDA for vitamin C is in milligrams (mg), but vitamin C labels may list grams (g) or micrograms (mcg).

• 1 milligram (mg) = 1,000 micrograms (mcg)
• 1 gram (g) = 1,000 milligrams

Dietary supplements aren't regulated by the FDA. When possible, choose a supplement that's been tested by a trusted third party, such as:

• ConsumerLabs

This ensures purity and that the contents match the label; however, it doesn't guarantee effectiveness.

Vitamin C supplements have been marketed for many conditions. Ultimately, it's the best treatment for vitamin C deficiency.

As an antioxidant and anti-inflammatory, vitamin C has been studied for its uses in heart disease prevention, gout, immunity, and more.

It is best to get vitamin C from your food. But if you don't, a supplement can help you meet your goals. Talk to your healthcare provider before taking supplements.

The right dosage depends on several factors, including age and medical conditions. In addition, vitamin C can interact with certain medications and cause side effects at high levels, so it is important to discuss with your healthcare provider whether supplementation is appropriate for you.

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Holford P, Carr AC, Jovic TH, et al. Vitamin C-an adjunctive therapy for respiratory infection, sepsis and COVID-19 .  Nutrients . 2020;12(12):3760. doi:10.3390/nu12123760

Pullar JM, Carr AC, Vissers MCM. The roles of vitamin C in skin health .  Nutrients . 2017;9(8):866. doi:10.3390/nu9080866

Nakajima M, Kojiro M, Aso S, et al. Effect of high-dose vitamin C therapy on severe burn patients: a nationwide cohort study .  Crit Care . 2019;23(1):407. doi:10.1186/s13054-019-2693-1

Harvard University, T.H. Chan School of Public Health. Collagen .

Ran L, Zhao W, Wang J, et al. Extra dose of vitamin c based on a daily supplementation shortens the common cold: a meta-analysis of 9 randomized controlled trials. BioMed Research International . 2018;2018:1-12.

Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev . 2013;(1):CD000980. doi:10.1002/14651858.CD000980.pub4

Hemilä H, Chalker E. Vitamin C reduces the severity of common colds: a meta-analysis . BMC Public Health . 2023;23(1):2468. doi:10.1186/s12889-023-17229-8

Cerullo G, Negro M, Parimbelli M, et al. The long history of vitamin C: From prevention of the common cold to potential aid in the treatment of COVID-19 . Front Immunol . 2020; 11:574029. doi:10.3389/fimmu.2020.574029

Quidel S, Gómez S, Bravo-Soto G, Ortigoze A. What are the effects of vitamin C on the duration and severity of the common cold? Medwave . 2018;18(5):e7260. doi:10.5867/medwave.2018.06.7260

Evans JR, Lawrenson JG. Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration . Cochrane Database Syst Rev . 2023;9(9):CD000254. doi:10.1002/14651858.CD000254.pub5

Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8 . Arch Ophthalmol . 2001;119(10):1417-1436. doi:10.1001/archopht.119.10.1417

Zampatti S, Ricci F, Cusumano A, Marsella LT, Novelli G, Giardina E. Review of nutrient actions on age-related macular degeneration . Nutr Res . 2014;34(2):95–105. doi:10.1016/j.nutres.2013.10.011

The Cochrane Collaboration. Preventing dementia: do vitamin and mineral supplements have a role?

Kocot J, Luchowska-Kocot D, Kiełczykowska M, Musik I, Kurzepa J. Does vitamin C influence neurodegenerative diseases and psychiatric disorders?   Nutrients . 2017;9(7):659. doi:10.3390/nu9070659

Zhou F, Xie X, Zhang H, Liu T. Effect of antioxidant intake patterns on risks of dementia and cognitive decline . Eur Geriatr Med . 2023;14(1):9-17. doi:10.1007/s41999-022-00720-7

Hantikainen E, Lagerros YT, Ye W, et al.  Dietary antioxidants and the risk of Parkinson disease. The Swedish National March Cohort .  Neurology.  2021;96(6):e895-e903. doi:10.1212/WNL.0000000000011373

Rowe S, Carr AC. Global vitamin C status and prevalence of deficiency: a cause for concern? Nutrients . 2020;12(7):2008. doi:10.3390/nu12072008

National Center for Advancing Translational Sciences. Genetic and Rare Diseases Information Center. Scurvy .

Miraj F, Karda IWAM, Abdullah A, Dionysios E. Lessons learned from "the great mimicker disease": A retrospective study of 18 patients with scurvy . J Child Orthop . 2023;17(6):618-625. doi:10.1177/18632521231213150

Marik PE. Is intravenous vitamin C contraindicated in patients with G6PD deficiency? Critical Care . 2019. doi:10.1186/s13054-019-2397-6

Martini N. Potion or poison? Vitamin C . J Prim Health Care . 2014;6(3):251. doi:10.1071/HC14251

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By Jennifer Lefton, MS, RD/N, CNSC, FAND Lefton is a registered dietitian/nutritionist and certified nutrition support clinician with over 20 years of experience in clinical nutrition.

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Vitamin C Experiment, Essay Example

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The aim of the experiment is to ascertain the saturation of Vitamin C in a variety of distinct fruit juices by means of t8itreation and to provide ranking for the vitamin C sources.

Introduction

Vitamins C (ascorbic acid) is a compound that dissolves in water and is one of the essential vitamins for life. Ascorbic acid is incorporated in a number of bodily functions, which are inclusive of the development of collagen in the joints, the production of dopamine, adrenaline and noradrenaline in the central nervous system. Vitamin C (ascorbic acid) is also responsible for the production of carnitine which is an essential component in the energy transference mechanism in the cellular mitochondria. A lack of ascorbic acid is the causal attribute of scurvy. It had been determined that protection from scurvy could be acquired by the consumption of citric fruits and sauerkraut. The research question that will be formulated is does the consumption of one daily fruit juice serving satisfy the recommended daily intake for Vitamin C in many of the industrialized nations including Australia, Canada, New Zealand, the United Kingdom and the United States. The minimum   recommended daily intake of vitamin C is 60 mg/ day. A Nobel prize award winning researcher, Linus Pauling recommended mega dosages of ascorbic acid on a daily basis in order to ward of diseases. Vitamins c is frequently applied as an antioxidant and antimicrobial in a number of food products. Ascorbic acid had been initially discovered in 1928 and in 1932 it had been determined as the biological agent which facilitated the deterrence of the dissemination of scurvy. The chemical structure had been documented in 1933 and had been verified by production.

Isomers which are enantiomers are reflections of one another. The L- enantiomer of Vitamin C is ascorbic acid. Ascorbic acid is a substance that has a stable solid quality which is inert with air and photoluminescence when found in an aqueous solution. The result of the oxidation process derives dehydroascorbic acid. When one of the species experiences oxidation, the other species experiences reduction. These are two processes which are complementary opposites. In the systems which have a biological quality, metabolic processes derive reactive oxidants. These oxidants have the capacity of reacting with molecules that are in their surroundings. consequently, causing damage to the cell. The human anatomy provides protection for its cells by applying a distinct collection of molecules which are designated antioxidants in order to detoxify and diminish the oxidants. The experiment applies this process in a redox/ oxidation titration procedure. In the process, Vitamin C decreases the orange hue of the iodine ion in order to produce the colorless solution. The reaction that is taking place in this experiment is the following:

H 4 O 6 + I 2 ? H 2 O 6 + 2I + 2H *

The process of volumetric evaluation is an approach that applies the assessment of volumes in order to ascertain the quantity of a substrate in a solution. In any of the reactions which occur between one or more categories of ions, the reaction equation demonstrates the stoichiometric proportions of the reacting molecules. The chemical reaction that is being researched is the process that occurs between the solutions of iodine and ascorbic acid. The chemical reaction equation details that the proportion of molecules of iodine to the molecules of ascorbic acid is in the ratio of one to one.  This infers that one mole of ascorbic acid reacts with one mole of vitamin C.

Iodine as an Indicator

The presences of an iodine cause the creation of a blue complex when starch is detected. As a result, iodine can respond as its proprietary indicator. As there is an excess of ascorbic acid, the iodine molecule which has an orange hue that is being aggregated from the bn8urrettte is experiencing reduction and loss its orange hue. When oxidation has taken place for all of the ascorbic acid, the iodine molecules which have been aggregated will no longer experience reduction. As a result of the starch solution that had been added, the aqueous solution will acquire a blue hue.

Materials and Experimental Procedure

• Iodine Solution
• Ascorbic acid. Acetic acid (0.2 M).
• Starch solution

Iodine Standardization Process

An iodine solution can be standardized regarding titration in correlation to a determinate saturation of sodium thiosulfate in accordance with the following chemical equation:

I 2 + 2S 2 O 3 ?2I + S 4 O 6

The sodium thiosulfate solution had been prepared prior to the experiment. The precise concentration is inscribed ion the label. This is the solution that will be applied for ascertaining the precise amount of iodine solution that is to be applied for the approximation of the Vitamin C content in the fruit juice.

Two hundred milliliters of iodine had been collected and placed into a flask which had a cap. The burette was prepared for the process of titration by rinsing and washing the burette with water and subsequently with a small amount of iodine solution. The cap was placed on the solution that was maintained in the flask.

One hundred and twenty milliliters of the sodium thiosulfate had been collected and placed into another clean and dry, two hundred and fifty milliliter flask. The precise concentration of the sodium thiosulfate solution was recorded.

A pipette was applied in order to transfer the sodium thiosulfate into a clan flask. Approximately half of a teaspoon of the starch in solid form had been applied in addition to 10 drops of acetic acid with a concentration of 0.2 M. The iodine solution was titrated to the point of realizing a color change for than interval of thirty seconds. The initial and final volumes were documented.

Sodium thiosulfate in the amount of 25 ml was transferred into a flask. The starch solution and the acetic acid had been aggregated. The titration was performed with the iodine solution. This was realized incrementally until there had been a 2 ml amount titrated. The ital. and the final volumes had been documented in the logbook.

Step four was repeated until there had been three titration values which were similar. The similarities were maintained to a tenth of a milliliter.

The calculation of the iodine solution was determined.

Outcome [Thiosulfate ions] = 2.040 x 10 – 3 M (Derived from label)

Table 1: Titration Outcomes for the Standardization Process of Iodine (Mean Titer = 33.675 ml).

In the trails the clear iodine solution was transformed to a blue hue.

Chemical reaction:

Consequently, one mole of iodine responds to one mole of S 2 O 3

25.00 ml of 2.040 x 10 – 3  M S 2 O 3 possesses 2.040 x 10 – 3   x 0.025moles of S 2 O 3 . Consequently, 33.675 ml

of the mystery Iodine solution possesses (2.040 x 10 – 3  x 0.025)/ 2 moles of iodine. As a result, 100 ml of the mystery iodine solution possesses (2.040 x 10 – 3  x 0.025 x 1000)/ (2 x 33.675) miles of iodine. Consequently, the saturation of the mystery iodine solution is 7.57 x 10 -4 M.

Determination of Vitamin C

Tem milliliters of fruit juice was weighed on the loading balance.

Five milliliters of fruit juice had been placed in the cylinder that had been applied for weighing.

The fruit juice had been placed into a 250 ml flask and was diluted with 20 ml of denatured water. A spoonful of starch solution had been aggregated with approximately ten drops of acetic acid which had a concentration of 0.2 M.

Steps one to three had been repeated for two different types of fruit juice.

The weight of the vitamin C in the fruit juice sample had been calculated. The data was recorded.

The recommended daily ingestion of Vitamin C in New Zealand and Australia is approximately 60 mg / daily. The mass of the fruit juice and the amount that would be needed to approximate 60 mg/ daily of vitamin C consumption.

Outcome: Fruit chosen- Orange

Weight of the fruit Juice One sample = 5.0 g

Weight of the fruit Juice sample two = 4.95 g

Table 2: Titration Outcomes for the Vitamin c determination of Orange Juice.

Molar weight of ascorbic acid is 176.12g/ mole

Chemical reaction: I 2 + Ascorbic acid ? @UI + Dehydroascorbic acid. Consequently, a mole of iodine responds to a mo9le of ascorbic acid

Fruit Juice One Sample

20.43 ml of 7.57 x 10 -4 M iodine solution possess 7.57 x 10 -4 M x 0.02043 mol of iodine.

As a result, 5.0 g of orange juice possesses 7.57 x 10 -4 M x 0.02043 mol of vitamin C.

As a result, 5.0 g of orange juice possesses 7.57 x 10 -4 M x 0.02043 x 176.12 g of Vitamin C

As a result, 5.0 g of orange juice possesses 2.7122 g of Vitamin C.

Consequently, the Vitamin C content in the fresh juice sample one is 2.7122mg/ 5.0 g = (54.2mg/g. + 54.0 mg /2) = 54.1 mg.

The hypothesis is disproven. The null hypothesis applies. The amount of vitamin c in one serving of juice is not sufficient to provide the recommended daily ingestion of vitamin C for New Zealand, Australia, Canada The UK and the United States.

Which one of the single servings of fruit juices provides the recommended daily ingestion of vitamin C for New Zealand, Australia, Canada, the UK and the United States?

All of the assessments of the amount of vitamin C contained in the different fruit juice samples had been determined. There had been two distinct values for each of the categories of fruit juice. The average amount of ascorbic acid that was maintained in each gram of juice was documented. The fruit juice which had the most substantial vitamin C content was reviewed.

In reality, it is discernable to know which of the fruit juices provides the greatest amount of vitamin C. The answerer derived may be different that the assessed values. The average value could have been skewed by two extremely elevated readings or one elevated reading for a sample. The portion of juice may have been outstanding. Usually, the measurements do not provide exact quantities, but instead they provide a distri9bution of numbers. When attempting to apply the information of which the distribution of numerical values in an actual real problem, the consideration of the baits of distribution which are the most relevant must be taken into account.

The two fruit juices which had the most elevated average vitamin C content were considered. In the discussion, they were delineated as Fruit Juice One and fruit Juice two. It would be easy to derive which of the juices was being examined from the data. In the event that fruit Juice one possessed the more elevated content of vitamin C, what is the statistical probability that if two new samples were to be analyzed, that fruit juice one would have a higher vitamin C content than fruit juice two. The method where the probability of the information derived from the collection of the fruit juices could be referenced. It is designated the term the sign test.

AS table had been drawn in the, logbook which detailed all of the collections’ assessments for fruit juice on the left side of the table. On the upper part of the table, the collections’ assessments for fruit juice two would be placed. The outcome is a grid with thirty-six boxes. An X had been drawn in each of the boxes where the reading of the fruit juice sample one had been greater than the value of fruit juice sample two. The statistical probability that the fruit juice sample one emerges as the victor in the comparison with the fruit juice sample two is equivalent to the proportion of the boxes in the table which have the cross. tabulate the fraction and document the fraction in the logbook.

Table 3: The statistical probability that fruit juice sample one would have a more solvated reading in the following sample is 24/ 67 = 0.6667

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10: Vitamin C Analysis (Experiment)

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• To standardize a \(\ce{KIO3}\) solution using a redox titration.
• To analyze an unknown and commercial product for vitamin C content via titration.
• To compare your results for the commercial product with those published on the label.

Note: You will need to bring a powdered or liquid drink, health product, fruit samples, or other commercial sample to lab for vitamin C analysis. You will need enough to make 500 mL of sample for use in 3-5 titrations. Be sure the product you select actually contains vitamin C (as listed on the label or in a text or website) and be sure to save the label or reference for comparison to your final results. Be careful to only select products where the actual vitamin C content in mg or percent of RDA (recommended daily allowance) is listed. The best samples are lightly colored and/or easily pulverized.

The two reactions we will use in this experiment are:

\[\ce{KIO3(aq) + 6 H+(aq) +5 I- (aq)→ 3 I2(aq) + 3 H2O(l) + K+(aq) } \quad \quad \text{generation of }\ce{I2} \label{1}\]

\[\underbrace{\ce{C6H8O6(aq)}}_{\text{vitamin C(ascorbic acid)}}\ce{ + I2(aq) →C6H6O6(aq) +2 I- (aq) + 2 H+(aq) } \quad \quad \text{oxidation of vitamin C}\label{2}\]

Reaction \ref{1} generates aqueous iodine, \(\ce{I2}\) ( aq ). This is then used to oxidize vitamin C (ascorbic acid, \(\ce{C6H8O6}\)) in reaction \ref{2}. Both of these reactions require acidic conditions and so dilute hydrochloric acid, \(\ce{HCl}\) ( aq ), will be added to the reaction mixture. Reaction one also requires a source of dissolved iodide ions, \(\ce{I^-}\) ( aq ). This will be provided by adding solid potassium iodide, \(\ce{KI}\) ( s ), to the reaction mixture.

This is a redox titration. The two relevant half reactions for reaction \ref{2} above are:

Reduction half reaction for Iodine at pH 5:

\[\ce{I2 +2e^{⎯} → 2I^{⎯}}\]

Oxidation half reaction for vitamin C (\(\ce{C6H8O6}\)) at pH 5:

A few drops of starch solution will be added to help determine the titration endpoint. When the vitamin C (ascorbic acid) is completely oxidized, the iodine, \(\ce{I2}\) ( aq ), will begin to build up and will react with the iodide ions, \(\ce{I^-}\) ( aq ), already present to form a highly colored blue \(\ce{I3^-}\)-starch complex, indicating the endpoint of our titration.

Vitamin C: An Important Chemical Substance

Vitamin C , known chemically as ascorbic acid , is an important component of a healthy diet. The history of Vitamin C revolves around the history of the human disease scurvy, probably the first human illness to be recognized as a deficiency disease. Its symptoms include exhaustion, massive hemorrhaging of flesh and gums, general weakness and diarrhea. Resultant death was common. Scurvy is a disease unique to guinea pigs, various primates, and humans. All other animal species have an enzyme which catalyzes the oxidation of L- gluconactone to L-ascorbic acid, allowing them to synthesize Vitamin C in amounts adequate for metabolic needs.

L-Ascorbic Acid -- Vitamin C

As early as 1536, Jacques Cartier, a French explorer, reported the miraculous curative effects of infusions of pine bark and needles used by Native Americans. These items are now known to be good sources of ascorbic acid. However, some 400 years were to pass before Vitamin C was isolated, characterized, and synthesized. In the late 1700's, the British Navy ordered the use of limes on ships to prevent scurvy. This practice was for many years considered to be quackery by the merchant marines, and the Navy sailors became known as “Limeys”. At that time scurvy aboard sailing vessels was a serious problem with often up to 50% of the crew dying from scurvy on long voyages.

The RDA ( Recommended Daily Allowance ) for Vitamin C put forward by the Food and Nutrition Board of the National Research Counsel is 60 mg/day for adults. It is recommended that pregnant women consume an additional 20 mg/day. Lactating women are encouraged to take an additional 40 mg/day in order to assure an adequate supply of Vitamin C in breast milk. Medical research shows that 10 mg/day of Vitamin C will prevent scurvy in adults. There has been much controversy over speculation that Vitamin C intake should be much higher than the RDA for the prevention of colds and flu. Linus Pauling, winner of both a Nobel Prize in Chemistry and the Nobel Peace Prize, has argued in his book, Vitamin C and the Common Cold , that humans should be consuming around 500 mg of Vitamin C a day (considered by many doctors to be an excessive amount) to help ward off the common cold and prevent cancer.

Vitamin C is a six carbon chain, closely related chemically to glucose. It was first isolated in 1928 by the Hungarian-born scientist Szent-Gyorgi and structurally characterized by Haworth in 1933. In 1934, Rechstein worked out a simple, inexpensive, four-step process for synthesizing ascorbic acid from glucose. This method has been used for commercial synthesis of Vitamin C. Vitamin C occurs naturally primarily in fresh fruits and vegetables.

Table 1: Vitamin C content of some foodstuffs

From Roberts, Hollenberg, and Postman, General Chemistry in the Laboratory .

Work in groups of three, dividing the work into three parts (standardization, unknown analysis, and food products) among your group members and then compare data if you are to finish in one period. Work carefully: your grade for this experiment depends on the accuracy and precision of each of your final results.

Materials and Equipment

You will need the following additional equipment for this experiment: 3 Burets, 1 Mortar and pestle, 1 Buret stand

Avoid contact with iodine solutions, as they will stain your skin. Wear safety glasses at all times during the experiment.

WASTE DISPOSAL : You may pour the blue colored titrated solutions into the sink. However, all unused \(\ce{KIO3}\) (after finishing parts A-C) must go in a waste container for disposal. This applies to all three parts of the experiment.

Proper Titration Techniques

Using a Buret

Proper use of a buret is critical to performing accurate titrations. Your instructor will demonstrate the techniques described here.

• Rinsing: Always rinse a buret (including the tip) before filling it with a new solution. You should rinse the buret first with deionized water, and then twice with approximately 10-mL aliquots of the solution you will be using in the buret. Be sure to swirl the solution to rinse all surfaces. If you are using an acid or base solution be careful to avoid spilling the solution on hands or clothing.
• Filling: Mount the buret on a buret stand. Be sure that the tip fits snuggly into the buret and is pressed all the way in. If the tip is excessively loose, exchange it for a tighter fitting one. Using a funnel rinsed in the same manner as the buret, fill the buret with the titrant to just below the 0.00 mL mark. There is no need to fill the buret to exactly 0.00 mL since you will use the difference between the ending and starting volumes to determine the amount delivered. When the buret is full, remove the funnel as drops remaining in or around the funnel can creep down and alter your measured volume. If you overfill the buret, drain a small amount into an empty beaker. Do not re-use this "extra" solution as it may have been contaminated by the beaker or diluted slightly by any water present in the beaker. Always pour fresh solution into the buret.
• Removing Air Bubbles: Often air bubbles will be trapped in the tip of a newly filled buret. These can be difficult to see and troublesome as they alter the measured volume when they escape. To remove air bubbles hold the buret over an open beaker and open the stopcock fully to allow solution to flow out of the buret. Your instructor will demonstrate this technique. Refill the buret as necessary.
• Reading the Buret: You should always read the volume in a buret from the bottom of the meniscus viewed at eye level (see Figure 1). A black or white card held up behind the buret helps with making this reading. Burets are accurate to ±0.02 mL and all readings should be recorded to two decimal places. Be sure to record both the starting and ending volumes when performing a titration. The difference is the volume delivered.

Figure 1: Reading a Buret

Good Titration Techniques

Throughout your scientific careers you will probably be expected to perform titrations; it is important that you learn proper technique. In performing a titration generally an indicator that changes color is added to a solution to be titrated (although modern instruments can now perform titrations automatically by spectroscopically monitoring the absorbance). Add titrant from the buret dropwise , swirling between drops to determine if a color change has occurred. Only if you know the approximate end-point of a titration should you add titrant faster, but when you come within a few milliliters of the endpoint you should begin to slow down and add titrant dropwise.

As you become proficient in performing titrations you will get a "feeling" for how much to open the stopcock to deliver just one drop of titrant. Some people become so proficient that they can titrate virtually "automatically" by allowing the titrant to drip out of the buret dropwise while keeping a hand on the stopcock, and swirling the solution with the other hand. If you do this, be sure that the rate at which drops are dispensed is slow enough that you can stop the flow before the next drop forms! Overshooting an end-point by even one drop is often cause for having to repeat an entire titration. Generally, this will cost you more time than you will gain from a slightly faster droping rate.

Refill the buret between titrations so you won’t go below the last mark. If a titration requires more than the full volume of the buret, you should either use a larger buret or a more concentrated titrant. Refilling the buret in the middle of a trial introduces more error than is generally acceptable for analytical work.

Set-up and Preparation of Equipment

• Clean and rinse a large 600-mL beaker using deionized water. Label this beaker “standard \(\ce{KIO3}\) solution.”
• From the large stock bottles of ~0.01 M \(\ce{KIO3}\) obtain about 600 mL of \(\ce{KIO3}\) solution. This should be enough \(\ce{KIO3}\) for your group for all three parts of the experiment including rinsings. The reason for collecting one beaker of stock is there is no guarantee that different batches of \(\ce{KIO3}\) from the stockroom will have the same exact molarity. By having one beaker of stock you ensure that all your trials come from the same solution. (If you run out of stock or spill this solution accidentally you will need to repeat part A on the new solution).
• Clean and rinse three burets once with deionized water and then twice with small (5-10 ml) aliquots of standard \(\ce{KIO3}\) from your large beaker. Pour the rinsings into a waste beaker.
• Fill each of the burets (one for each part of the experiment) with \(\ce{KIO3}\) from your beaker. Remove any air bubbles from the tips. The starting volumes in each of the burets should be between 0.00 mL and 2.00 mL. If you use a funnel to fill the burets be sure it is cleaned and rinsed in the same way as the burets and removed from the buret before you make any readings to avoid dripping from the funnel into the buret.

Each of the following parts should be performed simultaneously by different members of your group. You do not have enough time to do these sequentially and finish in one lab period.

Part A: Standardization of your \(\ce{KIO3}\) solution

The \(\ce{KIO3}\) solution has an approximate concentration of about ~0.01 M. You will need to determine exactly what the molarity is to three significant figures. Your final calculated results for each trial of this experiment should differ by less than ± 0.0005 M. Any trials outside this range should be repeated. You will need to calculate in advance how many grams of pure Vitamin C powder (ascorbic acid, \(\ce{C6H8O6}\)) you will need to do this standardization (this is part of your prelaboratory exercise). Remember that your buret holds a maximum of 50.00 mL of solution and ideally you would like to use between 25-35 mL of solution for each titration (enough to get an accurate measurement, but not more than the buret holds).

• Calculate the approximate mass of ascorbic acid you will need and have your instructor initial your calculations on the data sheet.
• Weigh out approximately this amount of ascorbic acid directly into a 250-mL Erlenmeyer flask. Do not use another container to transfer the ascorbic acid as any loss would result in a serious systematic error. Record the mass added in each trial to three decimal places in your data table. It is not necessary that you weigh out the exact mass you calculated, so long as you record the actual mass of ascorbic acid added in each trial for your final calculations.
• Dissolve the solid ascorbic acid in 50-100 mL of deionized water in an Erlenmeyer flask.
• Add approximately 0.5-0.6 g of \(\ce{KI}\), 5-6 mL of 1 M \(\ce{HCl}\), and 3-4 drops of 0.5% starch solution to the flask. Swirl to thoroughly mix reagents.
• Begin your titration. As the \(\ce{KIO3}\) solution is added, you will see a dark blue (or sometimes yellow) color start to form as the endpoint is approached. While adding the \(\ce{KIO3}\) swirl the flask to remove the color. The endpoint occurs when the dark blue color does not fade after 20 seconds of swirling.
• Calculate the molarity of this sample. Repeat the procedure until you have three trials where your final calculated molarities differ by less than ± 0.0005 M.

Part B: Vitamin C Unknown (internal control standard)

• Obtain two Vitamin C tablets containing an unknown quantity of Vitamin C from your instructor.
• Weigh each tablet and determine the average mass of a single tablet.
• Grind the tablets into a fine powder using a mortar and pestle.
• Weigh out approximately 0.20-0.25 grams of the powdered unknown directly into a 250-mL Erlenmeyer flask. Do not use another container to transfer the sample as any loss would result in a serious systematic error. Record the mass added in each trial to three decimal places in your data table.
• Dissolve the sample in about 100 mL of deionized water and swirl well. Note that not all of the tablet may dissolve as commercial vitamin pills often use calcium carbonate (which is insoluble in water) as a solid binder.
• Add approximately 0.5-0.6 g of \(\ce{KI}\), 5-6 mL of 1 M \(\ce{HCl}\), and 2-3 drops of 0.5% starch solution to the flask before beginning your titration. Swirl to mix.
• Perform two more trials. If the first titration requires less than 20 mL of \(\ce{KIO3}\), increase the mass of unknown slightly in subsequent trials.
• Calculate milligrams of ascorbic acid per gram of sample and using the average mass of a tablet, determine the number of milligrams of Vitamin C contained in each tablet. Be sure to use the average molarity for \(\ce{KIO3}\) determined in Part A for these calculations. Your results should be accurate to at least three significant figures. Repeat any trials that seem to differ significantly from your average.

Part C: Fruit juices, foods, health-products, and powdered drink mixes

Solids samples

• Pulverize solid samples (such as vitamin pills, cereals, etc.) with a mortar and pestle. Powdered samples (such as drink mixes) may be used directly.
• Weigh out enough powdered sample, so that there will be about 100 mg of ascorbic acid (according to the percentage of the RDA or mg/serving listed by the manufacturer) in each trial.
• Add the sample to a 250-mL Erlenmeyer flask containing 50-100 mL of water. (Note: If your sample is highly colored, you might want to dissolve the KI in the water before adding the mix, so that you can be sure it dissolves).
• Begin your titration. As the \(\ce{KIO3}\) solution is added, you will see a dark blue (or sometimes yellow or black depending on the color of your sample) color start to form as the endpoint is approached. While adding the \(\ce{KIO3}\) swirl the flask to remove the color. The endpoint occurs when the dark color does not fade after 20 seconds of swirling.
• Calculate the milligrams of ascorbic acid per gram of sample. Be sure to use the average molarity determined for the \(\ce{KIO3}\) in Part A for these calculations. Your results should be accurate to at least three significant figures. Repeat any trials that seem to differ significantly from your average.

Liquid samples

• If you are using a pulpy juice, strain out the majority of the pulp using a cloth or filter.
• Using a graduated cylinder, measure out at least 100 mL of your liquid sample. Record the volume to three significant figures (you will calculate the mass of ascorbic acid per milliliter of juice).
• Add this liquid to an Erlenmeyer flask.
• Begin your titration. As the \(\ce{KIO3}\) solution is added, you will see a dark blue (or sometimes yellow or black depending on the color of your sample) color start to form as the endpoint is approached. While adding the \(\ce{KIO3}\) swirl the flask to remove the color. The endpoint occurs when the dark color does not fade after 20 seconds of swirling. With juices it sometimes takes a little longer for the blue color to fade, in which case the endpoint is where the color is permanent.
• Perform two more trials. If the first titration requires less than 20 mL of \(\ce{KIO3}\), increase the volume of unknown slightly in subsequent trials.
• Calculate the milligrams of ascorbic acid per milliliter of juice. Be sure to use the average molarity determined for the \(\ce{KIO3}\) in Part A for these calculations. Your results should be accurate to at least three significant figures. Repeat any trials that seem to differ significantly from your average.

Pre-laboratory Assignment: Vitamin C Analysis

• If an average lemon yields 40 mL of juice, and the juice contains 50 mg of Vitamin C per 100 mL of juice, how many lemons would one need to eat to consume the daily dose of Vitamin C recomended by Linus Pauling? Show all work.
• Why are \(\ce{HCl}\), \(\ce{KI}\), and starch solution added to each of our flasks before titrating in this experiment? What is the function of each?
• \(\ce{HCl}\):
• \(\ce{KI}\):
• A label states that a certain cold remedy contains 200% of the US Recommended Daily Allowance (RDA) of Vitamin C per serving, and that a single serving is one teaspoon (about 5 mL). Calculate the number of mg of Vitamin C per serving and per mL for this product. Show all work.
• Based on the balanced reactions \ref{1} and \ref{2} for the titration of Vitamin C, what is the mole ratio of \(\ce{KIO3}\) to Vitamin C from the combined equations?

_______ moles \(\ce{KIO3}\) : _______ moles Vitamin C (ascorbic acid)

• Assuming that you want to use about 35 mL of \(\ce{KIO3}\) for your standardization titration in part A, about how many grams of ascorbic acid should you use? (you will need this calculation to start the lab). Show all work.

Hint: you will need to use the approximate \(\ce{KIO3}\) molarity given in the lab instructions and the mole ratio you determined in the prior problem.

Lab Report: Vitamin C Analysis

Mass of ascorbic acid to be used for standardization of ~0.01 M \(\ce{KIO3}\): __________ g ______Instructor’s initials

Supporting calculations:

Standardization Titration Data:

*All values should be with in ±0.0005 M of the average; trials outside this range should be crossed out and a fourth trial done as a replacement. Express your values to the correct number of significant figures. Show all your calculations on the back of this sheet.

• Average Molarity of \(\ce{KIO3}\):

"Internal Control Sample" (unknown) code:

Mass of Tablet 1:

Mass of Tablet 2:

Average mass:

Control Standard (Unknown) Titration Data:

* Express your values to the correct number of significant figures. Show all your calculations on the back of this sheet.

• ____________mg/g
• ____________mg/tablet

Name of Sample Used: ________________________________________________________

• Briefly describe the sample you chose to examine and how you prepared it for analysis. You may continue on the back if necessary:

Part C Titration Data:

*Express your values to the correct number of significant figures. Show all your calculations on the back of this sheet.

Average ascorbic acid :

• What is the concentration of Vitamin C listed on the packaging by the manufacturer or given in the reference source? This can be given in units of %RDA, mg/g, mg/mL, mg/serving, or %RDA per serving. Be sure to include the exact units cited.
• Manufacturer’s claim: ____________________________ (value and units)
• Serving Size (if applicable): ________________________ (value and units)

____________ mg / g or mL

• If your reference comes from a text book or the internet give the citation below. If it comes from a product label please remove the label and attach it to this report.
• Using your average milligrams of Vitamin C per gram or milliliter of product from part C as the "correct" value, determine the percent error in the manufacturer or text’s claim (show calculations)?
• What can you conclude about the labeling of this product or reference value? How do you account for any discrepancies? Does the manufacturer or reference overstate or understate the amount of Vitamin C in the product? If so, why might they do this? Explain below. Use the back of this sheet if necessary.

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• Indian J Clin Biochem
• v.28(4); 2013 Oct

Vitamin C in Disease Prevention and Cure: An Overview

Shailja chambial.

Department of Biochemistry, All India Institute of Medical Sciences, Jodhpur, 342005 Rajasthan India

Shailendra Dwivedi

Kamla kant shukla, placheril j. john.

Department of Zoology, Centre for Advanced Studies, University of Rajasthan, Jaipur, 302004 India

Praveen Sharma

The recognition of vitamin C is associated with a history of an unrelenting search for the cause of the ancient haemorrhagic disease scurvy. Isolated in 1928, vitamin C is essential for the development and maintenance of connective tissues. It plays an important role in bone formation, wound healing and the maintenance of healthy gums. Vitamin C plays an important role in a number of metabolic functions including the activation of the B vitamin, folic acid, the conversion of cholesterol to bile acids and the conversion of the amino acid, tryptophan, to the neurotransmitter, serotonin. It is an antioxidant that protects body from free radical damage. It is used as therapeutic agent in many diseases and disorders. Vitamin C protects the immune system, reduces the severity of allergic reactions and helps to fight off infections. However the significance and beneficial effect of vitamin C in respect to human disease such as cancer, atherosclerosis, diabetes, neurodegenerative disease and metal toxicity however remains equivocal. Thus further continuous uninterrupted efforts may open new vistas to understand its significance in disease management.

Introduction

Vitamins are essential nutrients that are required for various biochemical and physiological processes in the body. It is well known that most of the vitamins cannot be synthesized in the body and hence their supplementation in diet is essential. Vitamins are classified on the basis of their solubility as water soluble (C and B complexes) and fat soluble vitamins (A, D, E, K). Vitamin C or ascorbic acid (AA) was first isolated in 1923 by Hungarian biochemist and Nobel laureate Szent-Gyorgyi and synthesized by Howarth and Hirst [ 1 ]. It exists in reduced [ascorbate] and oxidized forms as dehydroascorbic acid which are easily inter-convertible and biologically active thus it acts as important antioxidant. Vitamin C is easily oxidized acid and destroyed by oxygen, alkali and high temperature. Most of the plant and animal species have the ability to synthesize vitamin C from glucose and galactose through uronic acid pathway but man and other primates cannot do so because of deficiency of enzyme gulonolactone oxidase [EC 1.1.3.8] required for it’s biosynthesis. Deficiency of this enzyme is a result of a mutation which occurred approximately 40 million years ago [ 2 ].

The body requires vitamin C for normal physiological functions. It helps in the synthesis and metabolism of tyrosine, folic acid and tryptophan, hydroxylation of glycine, proline, lysine carnitine and catecholamine. It facilitates the conversion of cholesterol into bile acids and hence lowers blood cholesterol levels. It also increases the absorption of iron in the gut by reducing ferric to ferrous state. As an antioxidant, it protects the body from various deleterious effects of free radicals, pollutants and toxins. The therapeutic effect of vitamin C was explored by Linus Pauling however his work on therapeutic role of vitamin C in his later years generated much controversy yet he was the first to introduce the concept of high doses of vitamin C for the treatment of various conditions from common cold to cancer [ 3 ]. Since then mega doses of vitamin C have been widely used in the treatment and prevention of a large number of disorders like diabetes, atherosclerosis, common cold, cataracts, glaucoma, macular degeneration, stroke, heart diseases, cancer and so on.

Deficiency of this vitamin is often associated with anemia, infections, bleeding gums, scurvy, poor wound healing, capillary haemorrhage, muscle degeneration, atherosclerotic plaques and neurotic disturbances. For the correction of deficiency, vitamin C is often supplemented in large doses and unlike fat soluble vitamins, toxicity is rare. Recently the role of vitamin C in infection and immunity has also been investigated. In view of the vast biological, physiological functions and therapeutic role of vitamin C, this review is an attempt to summarise various evidences in this context.

Dietary Sources of Vitamin C

Vitamin C is found in citrus fruits, green peppers, red peppers, strawberries, tomatoes, broccoli, brussels sprouts, turnip, Indian gooseberry and other leafy vegetables. The animal sources are poor in vitamin C content and the level is usually <30–40 mg/100 g. Therefore plant sources become important because of high content of vitamin C up to 5,000 mg/100 g. It’s absorption in the buccal cavity is by passive diffusion however in gastrointestinal tract absorption is by active sodium dependent vitamin C transporters (SVCT) [ 4 , 5 ].

Vitamin C Bioavailability

Bioavailability or the effective concentration of vitamin C essentially depends on its effective absorption from intestine and renal excretion. Vitamin C, consumed either with diet or dietary supplements, is absorbed by the epithelial cells of the small intestine by SVCT1 or, subsequently diffuses into the surrounding capillaries and then the circulatory system [ 5 – 7 ]. Circulating AA is filtered from kidney capillary bed into the Bowman’s capsule through a general filtration mechanism. AA is reabsorbed through SVCT1 transporter in proximal convoluted tubule [ 6 ]. The difference between the amount of AA filtered and reabsorbed constitutes renal excretion [ 8 ]. Together, intestinal absorption and renal excretion controls the serum level of vitamin C and thus its bioavailability. At low concentrations, most vitamin C is absorbed in the small intestine and reabsorbed from the renal tubule [ 9 ]. However, at high concentrations, SVCT1 is down regulated [ 10 ] which limits the amount of AA absorbed from the intestine and kidney [ 11 ]. This imposes a physiological restriction on the maximal effective serum vitamin C concentration (or its bioavailability) that is attainable by oral consumption [ 12 ]. This value has been determined to be 200 mmol/L [ 12 ], although “normal” physiological serum concentrations of ascorbate in healthy humans range from 60 to 100 mmol/L [ 13 ]. Vitamin C levels in circulating blood cells, such as platelets, are much higher than the plasma [ 13 ], as these cells express the SVCT2 transporter [ 14 ], which mediates intracellular ascorbate accumulation [ 15 ].

Reduced bioavailability of vitamin C is often seen in stress, alcohol intake, smoking, fever, viral illnesses, usage of antibiotics, pain killers, exposure to petroleum products or carbon monoxide, heavy metals toxicity and so on. However, the precise mechanism behind low vitamin C level in the body is not well defined. Presumably, an increased utilization of this vitamin in these conditions and/or a decreased absorption from the gut could be a cause of decreased vitamin C level [ 16 ]. In the event of high consumption, AA and its metabolites such as dehydroascorbic acid, 2,3-diketogulonic acid and oxalic acid are excreted via kidney in humans. AA is generally non-toxic but at high doses (2–6 g/day) it can cause gastrointestinal disturbances or diarrhoea [ 17 , 18 ]. The side effects are generally not serious and can be easily reversed by reducing the intake of AA. Furthermore, there is no consistent and compelling data on serious health effects of vitamin C in humans [ 18 , 19 ].

Biochemical Functions of Vitamin C

The biochemical functions of AA are largely dependent on the oxido-reduction properties of l -AA which is a co-factor for hydroxylation and activity of mono-oxygenase enzymes in the synthesis of collagen, carnitine and neurotransmitters [ 20 ]. AA accelerates hydroxylation reactions by maintaining the active centre of metal ions in a reduced state for optimal activity of enzymes hydroxylase and oxygenase. Thus, it is crucial in the maintenance of collagen which represents about one-third of the total body protein. In an experimental study AA has been shown to have involvement in synthesis and release of type IV collagen into the culture medium [ 21 ]. Further, it has also been reported that AA 2-phosphate, a long-acting vitamin C derivative, stimulates both cell growth and the expression of mRNA for type III collagen in human osteoblast-like MG-63 cells and in normal human osteoblasts, as well as in human bone marrow mesenchymal stem cells, but not the expression of type I collagen in these cells [ 22 ]. However, in another study Kishimoto et al. [ 23 ] have observed that AA induced the expression of type 1 and type 4 collagen and SVCT2 in cultured human skin fibroblasts. Collagen constitutes the principal protein of skin, bones, teeth, cartilage, tendons, blood vessels, heart valves, inter vertebral discs, cornea, eye lens. AA is essential to maintain the enzyme prolyl and lysyl hydroxylase in an active form. AA deficiency results in reduced hydroxylation of proline and lysine, thus affecting collagen synthesis. AA is also an essential co-factor for hydroxylations involved in the synthesis of muscle carnitine “β-hydroxybutyric acid” [ 24 , 25 ]. Carnitine is required for the transport and transfer of long chain fatty acids into mitochondria for energy production. Further, AA is also a co-factor for the enzyme dopamine-β-hydroxylase, which catalyzes the conversion of neurotransmitter dopamine to norepinephrine [ 19 ] and hence essential for the synthesis of catecholamines. In addition, AA catalyzes other enzymatic reactions involving amidation necessary for maximal activity of hormones oxytocin, vasopressin, cholecystokinin and alpha-melanotropin [ 26 ]. It is also involved in the transformation of cholesterol to bile acids as it modulates the microsomal 7α-hydroxylation, the rate limiting reaction of cholesterol catabolism in liver [ 27 ]. Deficiency of AA affects this conversion and as a result cholesterol accumulates in the liver leading to hypercholesterolemia [ 28 , 29 ], cholesterol gall stones formation etc [ 30 , 31 ].

Vitamin C and Common Cold

Apart from the well accepted role of vitamin C in the prevention of scurvy, the most widely known health beneficial effect of AA is in the prevention and relief of common cold. Pauling was the first to introduce the concept of high dose of vitamin C and suggested that ingestion of 1–3 g of AA effectively prevents/ameliorates common cold [ 32 ]. The role of oral vitamin C in the prevention and treatment of cold however remains controversial despite many controlled studies [ 33 ]. A number of clinical trials with varying doses of AA showed that it does not have significant prophylactic effect, but reduces the severity and duration of symptoms of cold during the period of infection. Randomized and non-randomized trials on role of vitamin C in prevention and treatment of the common cold indicated that AA in dose of 1 g/day during severe winter months produced no beneficial effect on the incidences of common cold [ 34 ]. In both preventive and therapeutic trials, there was a consistent beneficial but generally modest therapeutic effect on the duration of cold symptoms. There was no clear indication of the relative benefits of different regimes of vitamin C doses. However, in trials that tested vitamin C after cold symptoms occurred, there was some evidence of greater benefits with larger doses than with lower doses [ 34 , 35 ]. Attenuation of immunity in common cold is well known. There has been a continuous debate about the role of AA in boosting immunity during rhinitis. AA has been shown to stimulate immune system by enhancing T-cell proliferation in response to infection. These cells are capable of lysing infected targets by producing large quantities of cytokines and by helping B cells to synthesize immunoglobulins to control inflammatory reactions. Further, it has been shown that AA blocks pathways that lead to apoptosis of T-cells and thus stimulate or maintain T-cell proliferation to attack the infection. This mechanism has been proposed for the enhanced immune response observed after administration of vitamin C during rhinitis [ 36 , 37 ].

Vitamin C and Tissue Healing

It is also fairly understood that wound healing requires synthesis and accumulation of collagen and subsequent cross-linking of the fibre to give new tensile strength to the damaged tissue. An early study demonstrated that maximum tensile strength of scar tissue in guinea pig was achieved after supplementation of vitamin C [ 38 ]. Since then various studies have been carried out to evaluate the role of AA in wound repair and healing/regeneration process as it stimulates collagen synthesis. Adequate supplies of AA are necessary for normal healing process especially for post-operative patients because there is rapid utilization of AA for the synthesis of collagen at the site of wound/burns during post-operative period hence, administration of 500 mg to 1.0 g/day of AA are recommended to accelerate the healing process [ 39 ]. Of late, Jagetia et al. [ 40 ] demonstrated that AA pre-treatment was beneficial in healing of irradiated wounds and suggested a vitamin C related therapeutic strategy to accelerate wound repair in such conditions and in the cases of combined injury situation.

Vitamin C and Iron

AA is known to enhance the availability and absorption of iron from non-heme iron sources [ 41 ]. It’s supplementation is found to facilitate the dietary absorption of iron. The reduction of iron by AA has been suggested to increase dietary absorption of non-heme iron [ 42 , 43 ]. Vitamin C rich fruits such as goose berry has been reported to increase the bioavailability of iron from staple cereals and pulses [ 44 ]. Recent observations are of the view that vitamin C inhibits the expression of hepcidin and by affecting erythropoietin receptor in HepG2 cells and the bioavailability of iron provides protection against anaemia due to iron deficiency [ 45 ]. Darius Lane et al. [ 46 ], has considered ascorbate as a novel modulator for the classical transferrin Fe + uptake pathway, acting through intracellular reductive mechanism. It is also well known that AA acts as a pro-oxidant in invitro in the presence of redox-active iron and might contribute to the formation of hydroxyl radical, which eventually may lead to lipid, DNA or protein oxidation [ 47 ]. Thus vitamin C supplementation in individuals with high iron and or bleomycin detectable iron in some preterm infants could be deleterious due to the production of oxidatively damaged molecules [ 48 – 51 ]. However, Proteggente et al. [ 52 ] have observed no pro-oxidant effect of AA supplementation on DNA damage in presence or absence of iron.

Vitamin C and Fertility

Vitamin C has been used in the management of male infertility on empirical grounds, particularly in the presence of non-specific seminal infections [ 53 ]. It’s presence in the seminal plasma of healthy adults in high concentration, ranging from 2.5 to 12 mg/dL, has been reported by various authors [ 54 , 55 ]. However, the precise role of vitamin C in relation to male reproduction is not yet clear. Chinoy [ 56 ] stated that AA was essential for the structural and functional integrity of androgen-dependent reproductive organs. Low concentration of vitamin C showed marked degenerative changes in the testes, epididymis and vas deferens of scorbutic guinea pigs [ 57 ]. Besides degeneration of the spermatogenic epithelium, steroidogenesis and plasma testosterone level also showed a decline [ 58 ]. On the other hand, excessive intake of vitamin C has been reported to cause reproductive failure in the males [ 59 ]. However, Sapra et al. [ 60 ] could not observe any definite effect of vitamin C supplementation on Leydig cells in guinea pigs. AA as the principle antioxidant in seminal plasma of fertile men, contributes up to 65 % of its total chain breaking antioxidant capacity [ 61 ]. It’s concentration in seminal plasma is almost ten times higher than plasma concentration. In various studies AA content in seminal plasma of fertile and infertile men was found to be significantly different [ 62 , 63 ] and the percentage of sperm with normal morphology correlated significantly with seminal AA in both the groups [ 63 – 65 ]. AA deficiency may lead to an increase in oxidative damage induced by reactive oxygen species (ROS) and increased ROS was observed in the semen of 25–45 % of infertile men [ 66 ]. This is further corroborated by association of decreased AA with increase seminal plasma lipid peroxidation as observed in human trial [ 67 ]. Others have also observed oxidative stress induced deleterious effect on male fertility [ 68 , 69 ]. Increased free radicals in the seminal plasma of infertile subjects by lowering the effective vitamin C levels may potentiate the deleterious effects that result in abnormal sperm parameters [ 70 , 71 ]. Further studies report that supplementation of AA leads to significant reduction in ROS concentration [ 72 , 73 ], sperm membrane lipid per-oxidation [ 73 ] and sperm DNA oxidation [ 74 ] and increased sperm quality [ 72 – 74 ]. The results of a recent animal experimental study indicated that, vitamin C improves antioxidant enzymes activity and significantly reduce MDA in testis compared with the test group [ 75 ]. Vitamin C supplementation as antioxidant in dose dependent manner in men may improve sperm quality [ 76 ]. It’s supplementation also increases progesterone levels in infertile women with luteal phase defect [ 77 ].

Vitamin C and Atherosclerosis

There are several publications on the role of vitamin C in lipid metabolism and atherogenesis with diverse observations. The significance of dietary inadequacy of vitamin C in the aetiology of dyslipidemia and atherosclerosis first became apparent from the clinical studies of Myasnikova in 1947. The study showed lowering of cholesterol level by administration of AA in the hypercholesterolemic patients [ 78 ]. Since then several authors have also persuaded similar studies. One reviewed the evidence for the role of vitamin C in bile acid synthesis [ 27 ] while others gave particular emphasis on the potential involvement of vitamin C in pathogenesis of atherosclerosis [ 79 , 80 ]. There are reports indicating increase in total body cholesterol and hypercholesterolemia in acutely scorbutic guinea pigs. However, some studies could not observe any effect of vitamin C in similar animal models [ 81 ]. Das et al. [ 82 ] observed that administration of AA lowers blood cholesterol, triglycerides, lipid per-oxidation and increases HDL cholesterol. Most of the earlier studies were conducted using rabbit as an animal model for examining vitamin C deficiency. As such rabbit is not a suitable model for such studies as it can synthesize AA unlike higher primates and human beings. It is difficult to elicit vitamin C deficiency in animal models. In view of the conflicting observations based on the acutely scorbutic animal model chosen by most of the workers, Ginter et al. [ 83 ] designed a model of chronic latent vitamin C deficiency in guinea pigs. This model in contrast to others, enabled the effect of AA deficiency on lipid metabolism and atherosclerosis to be followed in long term experiments. In protracted hypovitaminosis C lasting for 10 weeks, there was a considerable accumulation of cholesterol in liver and also increased concentration in serum [ 83 – 85 ].

It was also reported that the deficiency of vitamin C leads to enhanced accumulation of cholesterol in thoracic aorta along with pathomorphological changes in blood vessels [ 83 , 86 , 87 ]. Various human trials have also indicated vitamin C induced reduction in blood lipid levels in normal and hypercholesterolemic subjects [ 88 , 89 ]. Marc and Kothari and Sharma have further observed that vitamin C administration causes significant reduction in LDL and increase in HDL [ 87 ] and there by provides protection against CAD [ 87 , 90 ]. Similar observations have been given by others also [ 91 – 96 ]. Chronic AA deficiency in man can lead to impaired cholesterol metabolism resulting in atheromatous changes in the vascular system [ 87 ]. This is further supported by the observation that vitamin C lowers cholesterol [ 88 ] and reduces the risk of developing cardiovascular disease (CHD) [ 97 , 98 ]. Numerous studies have also looked into the association between AA intake and blood lipids. A large prospective epidemiological study in Finnish men and women suggested that high intake of AA was associated with a reduced risk of death from CHD in women than in men [ 98 ]. Similarly, several other studies showed that high intake of AA in American men and women appeared to benefit only women [ 97 , 99 ]. Yet, another cohort study suggested that cardiovascular mortality was reduced in both sexes by vitamin C [ 100 ]. It is likely that cholesterol lowering effect of vitamin C is affected by several factors like initial cholesterol levels, age and sex of the subjects, dose and mode of the administration. The influence of age may be important because SAA levels have been found to be lower in elderly as compared to adolescents [ 101 , 102 ] and therefore elderly subjects could be more responsive to the administration of vitamin C. In UK, a study showed that the risk of stroke in those with highest intake of vitamin C was only half that of subjects with the lowest intake. No evidence is suggestive of lower rate of CHD in those with high vitamin C intake [ 103 ]. A recent meta-analysis study on the role of AA and antioxidant vitamins also showed no evidence of significant benefit in prevention of CHD [ 104 ]. Thus, no conclusive evidence is available on the possible protective effect of AA supplementation on CHD.

Increased attention is being paid to involvement of low density lipoprotein (LDL) in atherogenesis. There are reports indicating that lipid peroxidation and oxidative modification of LDL are implicated in development of atherosclerosis [ 105 ]. Vitamin C provides protection against oxidative changes in LDL in different types of oxidative stress including metal induced oxidative stress [ 106 ]. Addition of iron to plasma devoid of AA resulted in lipid peroxidation, whereas endogenous and exogenous AA was found to inhibit the lipid oxidation in iron-over loaded human plasma [ 107 ]. In an invitro study, when AA was added to human serum supplemented with Cu 2+ , antioxidant activity were observed rather than pro-oxidant effects [ 108 ]. AA is known as important antioxidant that scavenges free radicals and thus primarily prevents the oxidation of LDL in aqueous medium [ 109 ]. In addition, invitro studies have also shown that AA strongly inhibits LDL oxidation by vascular endothelial cells at physiological concentrations [ 110 – 112 ]. An important factor that initiates atherosclerosis is the adhesion of leukocytes to the endothelium. Invivo studies have shown that AA inhibits leukocyte-endothelial cell interactions induced by cigarette smoke [ 113 , 114 ] or oxidized LDL [ 115 ]. Further, lipophilic derivatives of AA showed protective effect on lipid-peroxide induced endothelial injury [ 116 ]. In endothelial cells, AA prevented atherogenic modification of mildly oxidized LDL [ 110 ] and preserved α-tocopherol in both cells and LDL [ 117 ]. Although AA may not reverse established atherosclerosis, it can prevent the endothelial dysfunction that is the earliest sign of many vascular inflammatory conditions. AA is responsible for increased endothelial cell proliferation and also checks tumour necrosis factor (TNF) alpha induced endothelial cell growth inhibition. Vitamin C as antioxidant helps in endothelial cell proliferation and also correlated with expression of collagen IV in endothelial cells. Study has also shown that when proliferating endothelial cells were treated with AA, increased retinoblastoma protein (Rb) phosphorylation was observed with decreased level of p53 as compared to untreated cells. Furthermore, the addition of AA to TNF-alpha-treated proliferating endothelial cells blocked both the inhibition of retinoblastoma protein phosphorylation and enhanced p53 expression induced by TNF-alpha and TNF-alpha-induced apoptosis [ 117 ].

A number of studies were carried out in humans to determine the protective effect of AA supplementation (500–100 mg/day) on invivo and exvivo lipid peroxidation in healthy individuals and smokers with inconclusive findings. AA supplementation showed reduction or no change in lipid peroxidation products [ 111 , 118 – 122 ]. There are reports where vitamin C has been found to decrease LDL peroxidation even in passive smokers [ 123 ]. In this context, it is important to note that during exvivo LDL oxidation, AA is removed at initial stage of LDL isolation from plasma therefore, no change in exvivo appears [ 124 ]. May and Li, examined the role of vitamin C in oxidation of LDL which causes endothelial dysfunction, an important early manifestation of atherosclerosis. They observed that up-regulation of endothelial cell SVCT2 expression and function may help to maintain intracellular ascorbate during oxLDL-induced oxidative stress, and that ascorbate in turn can prevent this effect [ 125 ]. Overall, both invitro and invivo experiments showed that AA protects isolated LDL and plasma lipid peroxidation induced by various radicals or oxidants generating systems. However, there are reports in experimental animals that large doses of exogenous iron and AA promote the release of iron from iron binding proteins and also enhance invitro lipid peroxidation in serum. This finding supports the hypothesis that high intake of iron along with AA could increase invivo lipid peroxidation of LDL and therefore could increase risk of atherosclerosis [ 126 ]. However, Chen et al. [ 127 ], demonstrated that ascorbic acts as an anti-oxidant towards lipids even in presence of iron load invivo systems. Vitamin C also helps in prevention of atherosclerosis by strengthening the artery walls through its participation in the synthesis of collagen and by preventing the undesirable adhesion of white blood cells to damaged arteries [ 128 – 132 ].

Vitamin C and Cancer

The notion that vitamin C may have a preventive role in cancer was first proposed in 1949. It was demonstrated by Cameron et al. [ 133 – 135 ], that high-dose vitamin C improved the survival of patients with terminal cancer. However, the first documented study in which vitamin C was administered to cancer patients was carried out in the 1970s, by Pauling and Cameron. They gave 10 g (10,000 mg) of vitamin C per day to 100 terminally ill cancer patients and compared their outcome with 1,000 cancer patients who were given conventional therapy. It was observed that 10.3 % cancer patients receiving vitamin C survived while all patients on conventional therapy without vitamin C died [ 134 ]. Other studies have also confirmed these findings. Murata and Morishige showed in a study conducted on Japanese patients with uterus cancer receiving 5–30 g of vitamin C that these patients survived six times longer than those on vitamin C <4 g per day. When comparison was made between those supplemented with or without vitamin C, survival rate was 15 % higher in those supplemented with vitamin C [ 136 ]. The overwhelming evidence supports that a high intake of vitamin C is linked with a low risk for cancer of oesophagus, oral cavity, stomach, pancreas, cervix, rectum and breast [ 137 , 138 ] and also non-hormonal cancers [ 139 ]. One of the most important amenable determinants of cancer risk is diet. Several research panels and committees have independently concluded that high fruit and vegetable intake reduces the risk of different types of cancer [ 140 , 141 ] and mortality rate was also found to be inversely related to vitamin C intake [ 142 , 143 ]. However a study involving 34,000 post-menopausal women, reported no such association between the intake of vitamins A, C and E and a reduced risk of developing breast cancer [ 144 ]. Intravenous vitamin C has also been reported to have beneficial effect in advanced cancer [ 145 ]. Several mechanisms proposed indicating involvement of vitamin C in the treatment and prevention of cancer are: enhancing the immune system; stimulating the formation of collagen; preventing metastasis (spreading) by inhibiting enzymes; preventing viruses that can cause cancer; correction of vitamin C deficiency which is often associated with cancer patients; wound healing in cancer patients after surgery; enhancing the effectiveness of chemotherapy; reducing the toxicity of chemotherapy; preventing free radical damages and neutralising some carcinogens [ 146 ].

Recently a number of experimental studies have observed that different types of cancer cells either do not grow at high vitamin C concentration or it leads to tumour shrinkage [ 147 , 148 ]. Further recent experimental studies have also found that ascorbate supplementation hinders metastasis, tumour growth and inflammatory cytokine secretion as well as enhanced encapsulation of tumours in Gulo KO mice [ 149 , 150 ]. Reports have shown that intravenous injection increases vitamin C concentration more than 70 times in relation to oral administration and effectiveness of treatment is linked to vitamin C concentration [ 12 , 145 ]. Thus controversy is because of mode, dose and duration of administration.

Newly available pharmacokinetic data improved the understanding of the regulation of vitamin C transport, and the growing evidence on the therapeutic efficacy of vitamin C. This has stimulated interest to reassess the feasibility of using vitamin C in the prevention and treatment of cancer. Though different in their methodologies, most recent studies on vitamin C and cancer have two central themes:(1) the effects of high-dose AA on the development and progression of tumours; and (2) the mechanisms of action that may contribute to the anti-cancer effect [ 144 ]. Research has also refocused on the implications and applicability of high i.v. dose of vitamin C in cancer therapy. In contrast to normal physiological concentration of AA (0.1 mmol/L) pharmacological concentrations of AA (0.3–20 mmol/L) selectively targets and kills tumour cells in invitro. This tumour-killing phenomenon is attributable to the pro-oxidant property of vitamin C, which, at high concentration mediates the production of hydrogen peroxide thus provides a potential mechanism of action for the anti-tumour effect of vitamin C and it’s implication as a pro-drug in cancer treatment [ 145 , 147 ]. However, it is difficult to assess the precise contribution of vitamin C in the clinical outcome, as subjects under examination simultaneously receive different therapeutic treatments [ 151 ]. Therefore, the therapeutic value of high-dose vitamin C administration in cancer progression or remission is not unequivocally supported but i.v. administration of vitamin C in high doses improves the health-related quality of life even at the advanced stage of the disease [ 152 ].

Vitamin C and Diabetes

Diabetes is becoming a pandemic and numbers are expected to rise to 366 million (4.4 % of the global population) by 2030 [ 153 ]. In diabetic patients, long-term damage, dysfunction, and failure of different organs, especially the eyes (diabetic retinopathy), kidneys (diabetic nephropathy), nerves (diabetic neuropathy), heart (myocardial infarction), and blood vessels (atherosclerosis) are related to uncontrolled hyperglycaemia [ 154 – 156 ]. Hyperglycaemia induces oxidative stress [ 157 ] primarily by ROS [ 18 ]. There is convincing experimental and clinical evidence that the generation of ROS increases in both types of diabetes and that the onset of diabetes is closely associated with oxidative stress [ 158 ]. Vitamin C has been associated with decreased risk of developing diabetes mellitus (DM). In Norfolk Prospective Study the association between fruit and vegetable intake and plasma levels of vitamin C and risk of type 2 DM was established [ 159 ]. During 12-years of follow-up, 735 incident cases of diabetes were identified among nearly 21,000 participants. A significant inverse association was found between plasma levels of vitamin C and risk of diabetes (odds ratio = 0.38, 95 % confidence interval: 0.28–0.52) [ 159 ]. This is further supported by a study with longer follow up of 23 years which reported that antioxidants induced risk reduction of type 2 diabetes [ 160 ] and vitamin C level was found to be significantly lower in both insulin dependent and non dependent diabetes [ 161 , 162 ]. Vitamin C reduces fasting and postprandial oxidative stress [ 163 ]. Sharma et al. have observed reduced vitamin C levels in diabetic subjects. They further reported that vitamin C level is also associated with various components of metabolic syndrome and with the increment in component there is a sharp reduction in vitamin C level [ 164 ]. In recent experimental studies it has been found that Vitamin C and E supplementation relieves oxidative stress in the blood and tissues of diabetic aged rats by modulating the antioxidant system and lipid profile [ 165 , 166 ].

Diabetes is associated with various micro vascular and macro vascular complications. Hyperglycaemia in diabetes is responsible for micro vascular ROS generation which causes endothelial dysfunction [ 167 ] and vitamin C blocks acute hyperglycaemic impairment of endothelial function in diabetic subjects [ 168 ]. One of the most important micro vascular complications is diabetic nephropathy. According to statistical prediction, out of 30 million patients with diabetes in India, diabetic nephropathy is expected to develop in 6.66 million [ 169 ]. Qin et al. [ 170 ] reported that vitamin C supplementation significantly decreased podocyte injury in diabetic rats. Perhaps AA protects podocyte by increasing antioxidative capacity and ameliorating the renal oxidative stress [ 171 ]. The role of vitamin C in diabetic retinopathy has also been reported in various studies. Vitamin C and E supplementation reduces neovascularization, prevent the inhibition of retinal glutathione reductase, glutathione peroxidase and superoxide dismutase activities; hence vitamin C and E prevent oxidative stress induced retinopathy [ 172 – 174 ]. Neuropathy is also one of the micro vascular complications often manifested in uncontrolled DM. Some studies report that the role of vitamin C in diabetic neuropathy is not as well pronounced as other antioxidants [ 175 ]. Some suggest that the AA levels are significantly low in diabetic polyneuropathy patients [ 176 ]. Role of vitamin C and other dietary antioxidants have been reviewed by several authors with controversial findings [ 177 ].

Vitamin C and Immunity

Vitamin C affects several components of the human immune system. Vitamin C appears to play a role in a number of neutrophil functions including increased chemotaxis, increased particulate ingestion, enhanced lysozyme-mediated non-oxidative killing, protection against the toxic effects of superoxide anion radical, inhibition of the halide-peroxide-myeloperoxidase system without a pronounced bactericidal effect, and stimulation of the hexose monophosphate shunt [ 178 ].

The role of vitamin C seems to be more pronounced in cell mediated response instead of humoral immunity as the T-cell hyporesponsiveness was observed to be reversed in Crohn’s disease patients on oral supplementation of vitamin C. In the same study no effect was observed on humoral immunity [ 179 ]. Another study supports the fact that vitamin C acts with other micronutrients synergistically and enhances skin barrier function as well as protective activities of immune cells but its role in antibody protection is not as pronounced [ 180 ]. On the contrary animal studies support the role of supplementation of vitamin C in humoral immunity as it increases serum levels of antibodies [ 181 ] and C1q complement proteins [ 182 ] in guinea pigs, which cannot synthesize vitamin C like humans and hence depend on dietary supplementation. Vitamin C along with other micronutrients help in reverting potential damage caused by free radicals at cellular level and modulates immune cell functions through regulation of redox-sensitive transcription factors and affects production of cytokines and prostaglandins. Adequate intake of vitamins C along with other vitamins and micronutrients like B 6 , folate, B 12 , E, selenium, zinc, copper, and iron supports a Th1 cytokine-mediated immune response [ 183 , 184 ] with sufficient production of proinflammatory cytokines, which maintain an effective immune response. Supplementation with these micronutrients reverses the Th2 cell-mediated immune response to Th1 cytokine-regulated response with enhanced innate immunity [ 183 ].

Vitamin C inhibits the excessive activation of the immune system to prevent tissue damage. It also supports antibacterial activity, stimulates natural killer (NK) cells and differentiation of Th0 subset into Th1 subset [ 184 , 185 ]. In addition, vitamin C also modulates synthesis of proinflammatory cytokines, or expression of adhesive molecules [ 185 ].

Mikirova et al. [ 186 ] have demonstrated that intravenous vitamin C treatment reduces pro-inflammatory cytokines IL-1α, IL-2, IL-8, TNF-α, chemokine eotaxin and CRP in cancer patients. Several studies have shown that the modulation of inflammation by intravenous vitamin C correlated with decrease in tumour marker levels [ 186 – 188 ]. Studies conducted on human subjects reported that that plasma vitamin C and dietary intakes of vitamin C are inversely associated with some markers of the acute phase response and haemostasis that have been associated with greater risk of CVD and non-vascular disease. Plasma vitamin C, fruit intake, and dietary vitamin C intake were significantly and inversely associated with mean concentrations of C-reactive protein, an acute phase reactant, and tissue plasminogen activator antigen, a marker of endothelial dysfunction, even after adjustment for confounders. The findings suggest that vitamin C has anti-inflammatory effects and is associated with lower endothelial dysfunction in men with no history of CHD or diabetes [ 189 – 196 ]. Vitamin C concentrations in the plasma and leukocytes rapidly decline during infections and stress. Supplementation of vitamin C has been shown to improve components of the human immune system such as antimicrobial and NK cell activities, lymphocyte proliferation, chemotaxis, and delayed-type hypersensitivity as discussed above. Vitamin C contributes in maintenance of the redox integrity of cells and thereby protects them against ROS generated during the respiratory burst and in the inflammatory response [ 197 ].

Thus, vitamin C has diverse role as an antioxidant protecting the immune cells against intracellular ROS production during inflammatory response, acting as an enzymatic cofactor and maintaining tissue integrity and plays a crucial role in formation of skin, epithelial and endothelial barriers [ 185 ]. Of late vitamin C supplementation has been found to be beneficial in various inflammatory conditions.

Vitamin C and Heavy Metal Toxicity

Metals including iron, copper, chromium, and vanadium undergo redox cycling, while cadmium, mercury, and nickel, as well as lead deplete glutathione and protein-bound sulfhydryl groups, resulting in the production of ROS as superoxide ion, hydrogen peroxide, and hydroxyl radical. As a consequence, enhanced lipid peroxidation, DNA damage, and altered calcium and sulfhydryl homeostasis occur [ 198 ]. Various experimental studies report the beneficial effect of vitamin C against heavy metal toxicity. Lead is considered as one of the common environmental poison in which protective role of vitamin C is extensively studied. A recent experimental study based on histopathological examination revealed the diminution of detrimental effects of chronic lead intoxication on liver, kidneys, brain and testes [ 199 ]. In another study lead induced electrophysiological changes were inhibited in rat colon by AA administration [ 200 ]. The beneficial effect of AA on lead concentrations in human studies is however inconclusive. A large survey comprising of 19,578 participants (6–90 years) without prior history of lead poisoning reported that blood levels of AA are inversely related to plasma AA and recent dietary intake had no influence on blood levels. This study surmises that there may be a protective relationship between AA and lead [ 201 ].

Arsenic toxicity is essentially associated with lipid peroxidation and oxidative stress. Arsenic in drinking water may even cause chromosomal aberration leading to molecular disorders [ 202 ]. Arsenic exposure during gestation and lactation leads to significantly increased lipid peroxidation in the rat brain which was reversed by supplementation of vitamin C, E and Zn [ 203 ]. In another study arsenic induced normocytic and normochromic anemia as well as a significant increase in hemolysis, TBARS production, catalase activity, hyperlipidemia, and impairment in renal functions in mice pups during gestation and lactation which was partially reverted by the administration of AA [ 204 ]. Arsenic induced hepatotoxicity has also been reported by recent experimental studies which have suggested that vitamin C supplementation improves mitochondrial structure and function along with restriction of apoptosis due to caspase-3 inhibition in arsenic trioxide exposed rat liver. The overall report is of view that vitamin C and vitamin C rich fruits such as goose berry provides protection against metal induced hepatotoxicity [ 205 , 206 ].

Cadmium is an extremely toxic metal commonly found in industrial workplaces similar to lead and arsenic also causes lipid peroxidative changes in various tissues. An experimental study discussed protective role of vitamin C supplementation in lung and brain of rat exposed to excessive cadmium [ 207 ]. Vitamin C also reverted haematological changes in mercury and cadmium exposed Wistar rats [ 208 ]. Vitamin C was also observed to be protective against concomitant exposure to heavy metal and radiation in another experimental study [ 209 ].

Vitamin C and Neurodegenerative Disorders

Schizophrenia is one of the major neurological disorders associated with great deal of morbidity and economic burden. It is a multifactorial disease and hence has a poor outcome in spite of the best available treatments. It is worth mentioning that simple water soluble vitamin C, adequately present in fruits and vegetables had drawn attention of the psychiatrists almost seven decades ago for the treatment of schizophrenia. A study conducted on 12 schizophrenics showed that urinary excretion of vitamin C was significantly lower than healthy controls and intravenous injection of large dose of vitamin C produced improvement in mental condition in 75 % of patients [ 210 ]. In another study it was observed that vitamin C level was significantly low in plasma and urine of schizophrenics as compared to normal controls. Administration of vitamin C improved plasma vitamin C level and thus concluded that schizophrenic patients require higher levels of vitamin C than the suggested optimal AA requirement for healthy individuals [ 211 ]. Several investigators have implicated role of increased free radical generation in pathogenesis of schizophrenia. Alteration in the optimum activities of antioxidant enzymes [ 212 – 214 ] and related parameters of lipid peroxidation [ 215 , 216 ] in blood have been detected in schizophrenics. Brain contains large amount of unsaturated fatty acids, catecholamines and monoamines, which are the target molecules for lipid peroxidation [ 217 , 218 ]. Brain is rich in iron containing compounds and thus it is an easy target for lipid peroxidation through the formation of hydroxyl radicals. Monoamine and catecholamine oxidation also produces superoxide anions in the brain [ 219 ]. AA, an antioxidant vitamin, plays an important role in protecting free radical-induced damage in the brain. Dadheech et al. [ 220 ] reported the antioxidant deficit in schizophrenics and it was associated with increased MDA level in blood which is a marker for lipid peroxidation. Vitamin C is present in dopamine dominant areas at high concentrations in the brain tissue as compared to other organs [ 221 , 222 ]. Recently, Arvindakshan et al. [ 223 ] reported reduction in brief psychiatric rating scale (BPRS) and positive and negative syndrome scale score after supplementation with omega-3 fatty acids, vitamin C, and vitamin E. A decrease in the levels of tocopherol, total AA and reduced glutathione was found in schizophrenics compared to normal controls. Further a significant rise in oxidative stress and decreased antioxidant status was observed in the chronic stage of schizophrenia as compared to those in acute condition. A significant rise in dehydroascorbic acid with concomitant fall in reduced AA suggests scavenging action of AA and its utilization with increased oxidative stress as indicated by high blood malondialdehyde levels. Leucocyte AA, a better index of AA status was also found to be reduced in schizophrenics, suggesting depletion of body stores of AA and the condition worsened with advancing age [ 224 ].

Very few studies have examined the effect of vitamin C with typical antipsychotics in the treatment of schizophrenia. Oral supplementation of vitamin C with antipsychotic reverses AA levels, reduces oxidative stress, and improves BPRS score, hence both the drugs in combination can be used in the treatment of schizophrenia [ 225 ]. The findings of another study suggest that antioxidant supplement therapy as an adjuvant therapy is useful in patients with stress-induced psychiatric disorders [ 226 ]. There are also reports advocating beneficial effect of vitamin C in neurodegenerative disorders including Alzheimer’s disease. Overall there is large body of evidence supporting that maintaining healthy vitamin C level can have a protective function against age related cognitive decline but avoiding vitamin C deficiency is likely to be more beneficial than taking supplements on top of normal healthy diet [ 227 ].

Vitamin C papers

• PMID: 2928785
• DOI: 10.1126/science.2928785

Publication types

• Ascorbic Acid / history*
• Publishing / standards
• Ascorbic Acid