|Key Facts||In Our Multivitamin|
|Form absorbed||Ascorbic acid
|Active forms||Ascorbic acid
|Nutrient Reference Value||80 mg||% NRV||100%|
|Stored in||Not stored in body
Vitamin C, also known as ascorbic acid, is an essential water soluble vitamin which has several important functions in the body. It's structurally related to glucose, and consists of two inter-convertible compounds: L-ascorbic acid, and its oxidised derivative L-dehydroascorbic acid. (1-3)
Vitamin C is important for:
✔️ contributing to the protection of cells from oxidative stress
✔️ supporting the normal function of the immune system
✔️ maintaining the normal functioning of the nervous system
✔️ contributing to normal energy yielding metabolism.
Vitamin C is an important antioxidant, involved in the prevention of the damaging effects of free radicals. (2,3,11)
Vitamin C is needed as a cofactor for the neurotransmitters dopamine and noradrenaline. (3,4)
There's loads of scientific evidence of the effects of vitamin C on the body's innate immune system (non-specific defence mechanisms) and adaptive (pathogen specific) immune response. (5-8)
Vitamin C is considered an absolute requirement for two enzymes involved in the production of carnitine, which plays an important role in energy production. (2)
Foods that provide vitamin C (1)
Vitamin C is found in a wide range of fruits and vegetables. Good sources include:
- citrus fruit
- brussels sprouts
How much vitamin C do I need? (1,10)
Vitamin C can't be stored in the body, so you need to get it in your diet every day.
The amount of vitamin C that adults aged over 18 need is:
- 40 mg a day
How much is too much?Taking more than 1,000 mg per day of vitamin C can cause stomach pain, diarrhoea, and flatulence. These symptoms should disappear once you stop taking vitamin C supplements.
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Interactions with other nutrients
Absorption of metal ions may be altered by vitamin C. Vitamin C has been shown to regenerate other antioxidants within the body, including vitamin E. (11)
Absorption and bioavailability
Absorption of vitamin C in the gut is efficient. It occurs in the small intestine via a saturable active transport mechanism, meaning that while the absorption efficiency of low oral doses of vitamin C (less than 64 mg) may be as high as 98%, absorption efficiency decreases with increasing doses of the vitamin. Approximately 70%–90% of vitamin C is absorbed at moderate intakes of 30–180 mg/day. However, at doses above 1 g/day, absorption falls to less than 50% with unmetabolised ascorbic acid being excreted in the urine. (11)
Supplements typically contain vitamin C in the form of ascorbic acid, which has equivalent bioavailability to that of naturally occurring ascorbic acid in foods. Other forms of vitamin C supplements such as sodium ascorbate have been found to have no difference in bioavailability. (12-15)
Once absorbed, ascorbic acid is widely distributed in all tissues of the body. It is a strong reducing agent, involved in prevention of the damaging effects of free radicals.
- Frei, B.; England, L.; Ames, B.N. Ascorbate is an outstanding antioxidant in human blood plasma. Natl. Acad. Sci. USA 1989, 86, 6377-6381. (PubMed)
- Sadler, M.J.; Strain, J.J.; Caballero, B. Encyclopedia of human nutrition, Academic Press: San Diego, 1999.
- Shils, M.E.; Shike, M.; Ross, A.C.; Caballero, B.; Cousins, R. Modern Nutrition in Health and Disease, Lippincott Williams & Wilkins: Baltimore, 2006.
- Delafuente, J.C.; Prendergast, J.M.; Modigh, A. Immunologic modulation by vitamin C in the elderly. J. Immunopharmacol. 1986, 8, 205-211. (PubMed)
- Jacob, R.A.; Kelley, D.S.; Pianalto, F.S.; Swendseid, M.E.; Henning, S.M.; Zhang, J.Z.; Ames, B.N.; Fraga, C.G.; Peters, J.H. Immunocompetence and oxidant defense during ascorbate depletion of healthy men. J. Clin. Nutr. 1991, 54, 1302S-1309S. (PubMed)
- Bender, D.A. Nutritional Biochemistry of the Vitamins. Cambridge University Press: Cambridge, 2003.
- Garrow, J.S.; James, W.P.T.; Ralph, A. Human Nutrition and Dietetics. Churchill Livingstone: London; Edinburgh, 2000.
- Levin, M.; Katz, A.; Padayatty, S.J. Vitamin C. In: Modern Nutrition in Health and Disease; Shils, M.E.; Shike, M.; Ross, A.C.; Caballero, B.; Cousins, R.J., Eds. Lippincott Williams and Wilkins: Philadelphia, 2006; pp. 507-524.
- COMA; Dietary Reference Values for Food Energy and Nutrients for the United Kingdom; Report of the Panel on Dietary Reference Values; Committee on Medical Aspects of Food and Nutrition Policy, HMSO: London, 1991.
- Jacob, R.A.; Sotoudeh, G. Vitamin C function and status in chronic disease. Clin. Care 2002, 5, 66-74. (PubMed)
- Johnston, C.S.; Luo, B. Comparison of the absorption and excretion of three commercially available sources of vitamin C. Am. Diet Assoc. 1994, 94, 779-81. (PubMed)
- Bates, C.J. Bioavailability of vitamin C. J. Clin. Nutr. 1997, 51 (Suppl 1), S28-33. (PubMed)
- Mangels, A.R.; Block, G.; Frey, C.M.; Patterson, B.H.; Taylor, P.R.; Norkus, E.P. The bioavailability to humans of ascorbic acid from oranges, orange juice and cooked broccoli is similar to that of synthetic ascorbic acid. Nutr. 1993, 123, 1054-1061. (PubMed)
- Gregory, J.F. 3rd. Ascorbic acid bioavailability in foods and supplements. Rev. 1993, 51, 301-303. (PubMed)