Benefits and Uses of Vitamin C

Vitamin C supplements are often touted as a natural defense against a number of health conditions, such as the common cold. But while research shows that including enough vitamin C in your diet may protect against certain health problems, there's a lack of scientific evidence to support the use of vitamin C supplements.

Uses for Vitamin C Supplements

Found naturally in many fruits and vegetables, vitamin C is necessary for collagen formation, wound healing, and the repair and maintenance of cartilage, bones, and teeth.

In alternative medicine, vitamin C supplements offer antioxidant benefits and are purported to help the following health conditions:

colds
asthma
bronchitis
cardiovascular disease
cataracts
glaucoma
high blood pressure
Parkinson's disease

Some proponents also claim that vitamin C supplements can boost immunity, as well as aid in the prevention of cancer.

Health Benefits of Vitamin C Supplements:

To date, studies on the health effects of vitamin C supplements have yielded mixed results. Here's a look at some key findings:

1) Colds

In a 2007 review of 30 clinical trials (involving a total of 11,350 people), researchers concluded that vitamin C supplements did not help fight off colds in the normal population. However, the review's authors note that vitamin C supplements may be of some benefit to people living in extremely cold climates or to individuals exposed to brief periods of severe physical exercise (such as marathon runners).

More: 11 Natural Remedies for Colds | How to Boost Your Immune System Naturally

2) Heart Disease

Taking vitamin C supplements may not reduce risk of major cardiovascular events, according to a 2008 study of 14,641 male physicians (ages 50 and older at the study's start). For an average of eight years, study members took either a placebo or 500 mg of vitamin C in supplement form daily.

(In addition, the supplement group took 400 IU of vitamin E every other day.) Study results showed that neither vitamin E nor the vitamin C supplements had any significant effect on major cardiovascular events, such as stroke and heart attack.

3) Cancer

For a study published in 2009, 8,171 women took either a placebo or 500 mg of vitamin C in supplement form daily (as well as vitamin E and beta carotene every other day) for an average of 9.4 years. Study results showed that supplementation with vitamin C, vitamin E, or beta carotene did not help to prevent cancer.

Furthermore, a 2008 study involving 77,721 men and women (ages 50 to 76 years) found that long-term use of vitamin C supplements did not decrease risk of lung cancer. And in a 2004 review of 14 studies on antioxidant supplements and prevention of gastrointestinal cancers -- including four trials involving vitamin C supplements -- investigators found no evidence that antioxidant supplements prevented gastrointestinal cancers.

More: Can Resveratrol Keep You Cancer-Free? | Turmeric for Cancer Defense?

Caveats

Although vitamin C is generally considered safe, high doses may lead to a number of adverse effects, including kidney stones, severe diarrhea, and nausea. What's more, a 2008 study suggests that taking vitamin C supplements during cancer treatment may reduce the effectiveness of certain chemotherapy drugs.

Supplements haven't been tested for safety and due to the fact that dietary supplements are largely unregulated, the content of some products may differ from what is specified on the product label. Also keep in mind that the safety of supplements in pregnant women, nursing mothers, children, and those with medical conditions or who are taking medications has not been established.

You can get additional tips on using supplements here.

Using Vitamin C for Health

Given the lack of scientific support for the health benefits of vitamin C supplements, it's important not to rely on vitamin C products as a principal treatment of any health condition. In order to get enough vitamin C each day, look first to food sources like citrus, strawberries, tomatoes, peppers, leafy greens, and cantaloupe.

If you're looking to treat or prevent a certain condition with vitamin C supplements -- or any kind of dietary supplement -- make sure to consult your physician before you start your supplement regimen. Keep in mind that alternative medicine should not be used as a substitute for standard care. Self-treating a condition and avoiding or delaying standard care may have serious consequences.

_Sources:

_{Bjelakovic G, Nikolova D, Simonetti RG, Gluud C. "Antioxidant supplements for preventing gastrointestinal cancers." Cochrane Database Syst Rev. 2004 18;(4):CD004183.}

_{Douglas RM, Hemilä H, Chalker E, Treacy B. "Vitamin C for preventing and treating the common cold." Cochrane Database Syst Rev. 2007 18;(3):CD000980.}

_{Heaney ML, Gardner JR, Karasavvas N, Golde DW, Scheinberg DA, Smith EA, O'Connor OA. "Vitamin C antagonizes the cytotoxic effects of antineoplastic drugs." Cancer Res. 2008 1;68(19):8031-8.}

_{Lin J, Cook NR, Albert C, Zaharris E, Gaziano JM, Van Denburgh M, Buring JE, Manson JE. "Vitamins C and E and beta carotene supplementation and cancer risk: a randomized controlled trial." J Natl Cancer Inst. 2009 7;101(1):14-23.}

_{Memorial Sloan-Kettering Cancer Center. About herbs: Vitamin C. February 2009.}

_{National Institutes of Health. "Vitamin C (ascorbic acid): MedlinePlus Medical Encyclopedia". March 2010.}

_{National Institutes of Health. "Vitamin C (ascorbic acid): MedlinePlus Supplements". August 2009.}

_{Sesso HD, Buring JE, Christen WG, Kurth T, Belanger C, MacFadyen J, Bubes V, Manson JE, Glynn RJ, Gaziano JM. "Vitamins E and C in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial." JAMA. 2008 12;300(18):2123-33.}

_{Slatore CG, Littman AJ, Au DH, Satia JA, White E. "Long-term use of supplemental multivitamins, vitamin C, vitamin E, and folate does not reduce the risk of lung cancer." Am J Respir Crit Care Med. 2008 1;177(5):524-30.}