The Functions of Vitamin C in the Body

Vitamin C is a water-soluble vitamin, meaning that your body doesn’t store it. You have to get what you need from food, including citrus fruits, broccoli, tomatoes.



You need vitamin C for the GROWTH and REPAIR of tissues in all parts of your body. It helps the body make collagen, an important protein used to make SKIN, cartilage, tendons, ligaments and blood vessels. Vitamin C is needed for HEALING wounds, and for repairing and maintaining bones and teeth. It also helps the body absorb iron from nonheme (plant) sources.

Vitamin C is an important ANTIOXIDANT, along with vitamin E, beta-carotene, and many other plant-based nutrients. Antioxidants block some of the damage caused by free radicals, substances that damage DNA. The build up of free radicals over time may contribute to the ageing process and the development of health conditions such as cancer, heart disease, and arthritis. In this sense, vitamin C is an important ANTI-AGEING nutrient.

Contributors to Low Levels of Vitamin C and Signs of Deficiency 

Although being seriously deficient in vitamin C is rare nowadays, evidence suggests that many people may have low levels of vitamin C. Smoking cigarettes lowers the amount of vitamin C in the body, so smokers are at a higher risk of deficiency. Stress and pollution also drain vitamin C from the body, as does a constantly activated immune system (such as in allergies, leaky gut, auto-immune diseases).

Signs of vitamin deficiency include dry and splitting hair; gingivitis (inflammation of the gums) and bleeding gums; rough, dry, scaly skin; decreased wound-healing rate, easy bruising; nosebleeds; a decreased ability to ward off infections and accelerated ageing.

Over time, low blood levels of vitamin C contribute to the genesis of cardiovascular disease, type 2 diabetes and cancer.


The GSTT1 Gene Determines Your Ability to Process Vitamin C 

Research has shown that the amount of ascorbic acid circulating in the blood can differ between people even when the same amount of vitamin C is consumed. Some people do not process vitamin C from the diet as efficiently as others and are at a greater risk of vitamin C deficiency.  A recent study published in the American Journal of Clinical Nutrition has shown that the ability to process vitamin C depends on individual genetic variation in a gene called glutathione S-transferase T1 (GSTT1) (Cahill et al., 2009).

The GSTT1 Gene Has a Major Role in Detoxification

Glutathione S-transferases, or GSTs, are a large family of detoxifying enzymes that play a role in the glutathione-ascorbic acid antioxidant cycle in the human body. GSTs work with vitamin C to reduce oxidative stress and they can spare each other from oxidation. One class of the GST enzyme family is the theta class which consists of the GSTT1 enzyme.

People with the Del genotype are at a much greater risk of vitamin C deficiency

There is a common “deletion” variant in the gene that codes for the GSTT1 enzyme such that those who have two copies of the “deletion” variant do not produce a functional GSTT1 enzyme while those with even a single copy of the “insertion” version produce GSTT1 with normal functional activity.

The relationship between the deletion (or “Del”) variant of the GSTT1 gene and circulating levels of ascorbic acid have been shown to depend on the amount of vitamin C consumed (Cahill et al., 2009). This study examined 905 healthy young women and men and measured their dietary vitamin C intake and serum ascorbic acid levels. Subjects who did not meet the Recommended Dietary Allowance (RDA) for dietary vitamin C were significantly more likely to be vitamin C deficient (as assessed by serum ascorbic acid levels <11 μmol/L) than those who met the RDA. When the population was stratified by GSTT1 genotype, those with the Del genotype were at a much greater risk of vitamin C deficiency when not meeting the RDA.

Although individuals of East Asian ancestry are more likely to have the Del genotype compared to those of European ancestry (~ 50% vs. 20%), the effect of consuming less than the RDA for vitamin C and having the Del genotype on serum ascorbic acid was similar in both groups.


Regarding cancer risk, another study found that individuals with the Del genotype have reduced or no glutathione S-transferase activity and therefore may be unable to eliminate electrophilic carcinogens as efficiently. These individuals should take greater care to detoxify at frequent intervals (at least twice per year).

The Nutrigenomix test kit analyzes the Ins/Del variant to assess risk of vitamin C deficiency associated with low vitamin C intake. Subjects with the Del variant are at a much greater risk of vitamin C deficiency compared to those with the Ins variant.  Your nutritionist can use this information, along with other known factors, including health conditions and lifestyle factors, to develop a plan for you to achieve and maintain optimal vitamin C status.



Supporting Research

Afkhami-Ardekani M, Shojaoddiny-Ardekani A. Effect of vitamin C on blood glucose, serum lipids & serum insulin in type 2 diabetes patients. Indian J Med Res. 2007;126(5):471-4.

Antoon AY, Donovan DK. Burn Injuries. In: Behrman RE, Kliegman RM, Jenson HB, eds.Nelson Textbook of Pediatrics. Philadelphia, Pa: W.B. Saunders Company; 2000:287-294.

Audera C, Patulny RV, Sander BH, Douglas RM. Mega-dose vitamin C in treatment of the common cold: a randomised controlled trial. Med J Aust. 2001;175(7):359-362.

Braun BL, Fowles JB, Solberg L, Kind E, Healey M, Anderson R. Patient beliefs about the characteristics, causes, and care of the common cold: an update. J Fam Pract. 2000;49(2):153-156.

Bruno RM, Daghini E, Ghiadoni L, Sudano I, Rugani I, Varanini M, Passino C, Emdin M, Taddei S. Effect of acute administration of vitamin C on muscle sympathetic activity, cardaic sympathovagal balance, and baroreflex sensitivity in hypertensive patients. Am J Clin Nutr.2012;96(2):302-8.

Canter PH, Wider B, Ernst E. The antioxidant vitamins A, C, E and selenium in the treatment of arthritis: a systematic review of randomized clinical trials. Rheumatology. 2007;46(8):1223-33.

Cook NR, Albert CM, Gaziano JM, Zaharris E, MacFadyen J, Danielson E, Buring JE, Manson JE. A randomized factorial trial of vitamins C and E and beta carotene in the secondary prevention of cardiovascular events in women: results from the Women’s Antioxidant Cardiovascular Study. Arch Intern Med. 2007;167(15):1610-8.

Daniel TA, Nawarskas JJ. Vitamin C in the prevention of nitrate tolerance. Ann Pharacother. 2000;34(10):1193-1197.

Douglas RM, Chalker EB, Treacy B. Vitamin C for preventing and treating the common cold.Cochrane Database Syst Rev. 2000;(2):CD000980.

Dwyer JH, Merz NB, Shirocre AM, et al. Progression of early atherosclerosis and intake of vitamin C and vitamin E from supplements and food. The Los Angeles Atherosclerosis Study. 41st Annual Conference on Cardiovascular Disease Epidemiology and Prevention — Abstract P77. Circulation. 2001;103:1365d.

Gandini S, Merzenich H, Robertson C, Boyle P. Meta-analysis of studies on breast cancer risk and diet: the role of fruit and vegetable consumption and the intake of associated micronutrients. Eur J Cancer. 2000;36:636-646.

Head KA. Natural therapies for ocular disorders, part two: cataracts and glaucoma. Altern Med Rev. 2001;6(2):141-66.

Institute of Medicine. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Of Sciences. 2002. Accessed Sept. 14, 2007.

Juraschek SP, Guallar E, Appel LJ, Miller ER. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2012;95(5):1079-88.

Kaur B, Rowe BH, Ram FS. Vitamin C supplementation for asthma (Cochrane Review).Cochrane Database Syst Rev. 2001;4:CD000993.

Keligman: Nelson Textbook of Pediatrics, 19th ed. Philadelphia, PA: Saunders Elsevier. 2011.

Khaw KT, Bingham S, Welch A, et al. Relation between plasma ascorbic acid and mortality in men and women in EPIC-Norfolk prospective study: a prospective population study. European Prospective Investigation into Cancer and Nutrition. Lancet. 2001;357:657-63.

Kompauer I, Heinrich J, Wolfram G, Linseisen J. Association of carotenoids, tocopherols, and vitamin C in plasma with allergic rhinitis and allergic sensitization in adults. Public Health Nutr. 2006;9:472-9.

Kurowska EM, Spence JD, Jordan J, Wetmore S, Freeman DJ, Piche LA, Serratore P. HDL-cholesterol-raising effect of orange juice in subjects with hypercholesterolemia. Am J Clin Nutr. 2000;72(5):1095-1100.

Laight DW, Carrier MJ, Anggard EE. Antioxidants, diabetes and endothelial dysfunction.Cardiovasc Res. 2000;47:457-464.

Langlois M, Duprez D, Delanghe J, De Buyzere M, Clement DL. Serum vitamin C concentration is low in peripheral arterial disease and is associated with inflammation and severity of atherosclerosis. Circulation. 2001;103(14):1863-1868.

Lonn E. Do antioxidant vitamins protect against atherosclerosis? The proof is still lacking. J Am Coll Cardiol. 2001;38:1795-8.

Lykkesfeldt J, Christen S, Wallock LM, Chang HH, Jacob RA, Ames BN. Ascorbate is depleted by smoking and repleted by moderate supplementation: a study in male smokers and nonsmokers with matched dietary antioxidant intakes. Am J Clin Nutr. 2000;71(2):530-536.

Mares-Perlman JA, Lyle BJ, Klein R, et al. Vitamin supplement use and incident cataracts in a population-based study. Arch Ophthalmol. 2000;118:1556-63.

Masaki H. Role of antioxidants in the skin: anti-aging effects. J Dermatol Sci. 2010 May;58(2):85-90. Epub 2010 Mar 17. Review.

Masaki KH, Losonczy KG, Izmirlian G. Association of vitamin E and C supplement use with cognitive function and dementia in elderly men. Neurology. 2000;54:1265-1272.

National Academy of Sciences. Dietary Reference Intakes (DRIs): Recommended Intakes for Individuals, Vitamins. Accessed June 1, 2011.

Nurmatov U, Devereux G, Sheikh A. Nutrients and foods for the primary prevention of asthma and allergy: systematic review and meta-analysis. J Allergy Clin Immunol. 2011 Mar;127(3):724-33.e1-30. Review.

Ohnishi ST, Ohnishi T, Ogunmola GB. Sickle cell anemia: a potential nutritional approach for a molecular disease. Nutrition. 2000;16:330-8.

Padayatty SJ, Levine M. Reevaluation of ascorbate in cancer treatment: emerging evidence, open minds and serendipity. J Am Coll Nutr. 2000;19(4):423-425.

Ram FS, Rowe BH, Kaur B. Vitamin C supplementation for asthma. Cochrane Database Syst Rev. 2004;(3):CD000993.

Ravindran RD, Vashist P, Gupta SK, Young IS, Maraini G, Camparini M, Jayanthi R, John N, Fitzpatrick KE, Chakravarthy U, Ravilla TD, Fletcher AE. Inverse association of vitamin C with cataract in older people in India. Ophthalmology. 2011;118(10):1958-1965e2.

Rock CL, Michael CW, Reynolds RK, Ruffin MT. Prevention of cervix cancer. Crit Rev Oncol Hematol. 2000;33(3):169-185.

Shinke T, Shite J, Takaoka H, Hata K, Inoue N, Yoshikawa R, Matsumoto H, Masai H, Watanabe S, Ozawa T, Otake H, Matsumoto D, Hirata K, Yokoyama M. Vitamin C restores the contractile response to dobutamine and improves myocardial efficiency in patients with HF. Amer Heart J. 2007;154(4):645.e1-8.

Takkouche B, Regueira-Mendez C, Garcia-Closas R, Figueiras A, Gestal-Otero JJ. Intake of vitamin C and zinc and risk of common cold: a cohort study. Epidemiology. 2002;13(1):38-44.

Taylor A, Jacques PF, Chylack LT Jr, et al. Long-term intake of vitamins and carotenoids and odds of early age-related cortical and posterior subcapsular lens opacities. Am J Clin Nutr.2002;75(3):540-549.

Tofler GH, Stec JJ, Stubbe I, Beadle J, Feng D, Lipinska I, Taylor A. The effect of vitamin C supplementation on coagulability and lipid levels in healthy male subjects. Thromb Res. 2000;100(1):35-41.

Wolverton: Comprehensive Dermatologic Drug Therapy, 3rd ed. Philadelphia, PA: Saunders Elsevier. 2012.

Yokoyama T, Date C, Kokubo Y, Yoshiike N, Matsumura Y, Tanaka H. Serum vitamin C concentration was inversely associated with subsequent 20-year incidence of stroke in a Japanese rural community. The Shibata study. Stroke. 2000;31(10):2287-2294.

You WC, Brown LM, Zhang L, et al. Randomized double-blind factorial trial of three treatments to reduce the prevalence of precancerous gastric lesions. J Natl Cancer Inst. 2006;98:974-83.

Zheng SJ, Rautiainen S, Lindblad BE, Morgenstern R, Wolk A. High-dose supplements of viatmins C and E, low-dose multivitamins, and the risk of age-related macular degeneration.Am J Epidemiol. 2013;177(6):548-55.