What is vitamin C?

Vitamin C, also known as ascorbic acid, is a water-soluble micronutrient. Human beings cannot manufacture their own vitamin C and must rely on outside sources to obtain it, including food and supplements.

Vitamin C benefits

This vitamin is best known for its role in the synthesis of collagen, a connective tissue protein used as a structural component of skin, blood vessels, tendons, ligaments, and bone. A deficiency of vitamin C leads to the deficiency disease “scurvy,” characterized by insufficient collagen production. Although frequently thought of as a third-world deficiency disease, about 7% of Americans still suffer from scurvy.[1]

Another vitamin C function is the important role it plays as an antioxidant, protecting vital molecules in the body from damage by free radicals and reactive oxygen species. These molecules include proteins, lipids (fats), carbohydrates, and nucleic acids (DNA and RNA). Vitamin C also plays a complementary role with other antioxidants, such as vitamin E, helping to regenerate them from their oxidized form back into their reduced (active) form.[2,3]

Vitamin C is also needed for the synthesis of the neurotransmitter norepinephrine, which performs critical brain function, including an effect on mood. Likewise, it is needed for the synthesis of the amino acid carnitine, which is essential for the transport of fat into cellular mitochondria, where the fat is converted to energy or ATP.[4] In addition, vitamin C may also be involved in the metabolism of cholesterol to bile acids, which may be important for maintaining healthy cholesterol levels already within normal ranges.[5]

Another profound role that vitamin C plays is promoting the health of the immune system, including stimulating the production and function of white blood cells, including leukocytes, neutrophils, lymphocytes and phagocytes.[6,7,8,9,10,11,12] In fact, research has demonstrated that supplemental vitamin C increases serum levels of antibodies [13, 14] and C1q complement proteins.[15,16,17] Also, vitamin C has been shown to increase interferon levels in vitro,[18] and research on supplemental vitamin C has shown that it supports upper respiratory health.[19]

What has vitamin C?

Vitamin C is found in different fruits and vegetables. Although the vitamin C content varies depending upon the product, [20] about five servings (2½ cups) of fruits and vegetables should average out to about 200 mg of vitamin C. Rich sources of vitamin C include sweet red peppers, strawberries, oranges and orange juice, grapefruit and grapefruit juice, and broccoli. Other good sources are tomatoes and potatoes.

How much vitamin C should I take?

The RDA (Recommended Dietary Allowance) for vitamin C is 90 mg for men and 75 mg for women. The RDA for men and women smokers is 125 mg and 110 mg, respectively. However, studies conducted at the National Institutes of Health indicated that plasma and circulating cells in healthy subjects attain near-maximal concentrations of vitamin C at a dose of about 400 mg/day—a dose much higher than the current RDA.[21] This suggests that a daily intake of 400 mg is advisable. This can easily be obtained using a 500 mg capsule of vitamin C daily since 400 mg capsules of vitamin C aren’t commonly available.

References

1. Callus CA, Vella S, Ferry P. Scurvy is Back. Nutr Metab Insights. 2018; 11: 1178638818809097.
2. Carr AC, Frei B. Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. Am J Clin Nutr. 1999;69(6):1086-1107.
3. Bruno RS, Leonard SW, Atkinson J, et al. Faster plasma vitamin E disappearance in smokers is normalized by vitamin C supplementation. Free Radic Biol Med. 2006;40(4):689-697.
4. Carr AC, Frei B. Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. Am J Clin Nutr. 1999;69(6):1086-1107.
5. Simon JA, Hudes ES. Serum ascorbic acid and gallbladder disease prevalence among US adults: the Third National Health and Nutrition Examination Survey (NHANES III). Arch Intern Med. 2000;160(7):931-936.
6. Prinz W, Bortz R, Bregin B, Hersch M. The effect of ascorbic acid supplementation on some parameters of the human immunological defence system. Int J Vitam Nutr Res. 1977;47(3):248-257.
7. Vallance S. Relationships between ascorbic acid and serum proteins of the immune system. Br Med J. 1977;2(6084):437-438.
8. Kennes B, Dumont I, Brohee D, Hubert C, Neve P. Effect of vitamin C supplements on cell-mediated immunity in old people. Gerontology. 1983;29(5):305-310.
9. Panush RS, Delafuente JC, Katz P, Johnson J. Modulation of certain immunologic responses by vitamin C. III. Potentiation of in vitro and in vivo lymphocyte responses. Int J Vitam Nutr Res Suppl. 1982;23:35-47.
10. Jariwalla RJ, Harakeh S. Antiviral and immunomodulatory activities of ascorbic acid. In: Harris JR (ed). Subcellular Biochemistry. Vol. 25. Ascorbic Acid: Biochemistry and Biomedical Cell Biology. New York: Plenum Press; 1996:215-231.
11. Levy R, Shriker O, Porath A, Riesenberg K, Schlaeffer F. Vitamin C for the treatment of recurrent furunculosis in patients with imparied neutrophil functions. J Infect Dis. 1996;173(6):1502-1505.
12. Anderson R, Oosthuizen R, Maritz R, Theron A, Van Rensburg AJ. The effects of increasing weekly doses of ascorbate on certain cellular and humoral immune functions in normal volunteers. Am J Clin Nutr. 1980;33(1):71-76.
13. Prinz W, Bloch J, Gilich G, Mitchell G. A systematic study of the effect of vitamin C supplementation on the humoral immune response in ascorbate-dependent mammals. I. The antibody response to sheep red blood cells (a T-dependent antigen) in guinea pigs. Int J Vitam Nutr Res. 1980;50(3):294-300.
14. Feigen GA, Smith BH, Dix CE, et al. Enhancement of antibody production and protection against systemic anaphylaxis by large doses of vitamin C. Res Commun Chem Pathol Pharmacol. 1982;38(2):313-333.
15. Haskell BE, Johnston CS. Complement component C1q activity and ascorbic acid nutriture in guinea pigs. Am J Clin Nutr. 1991;54(6 Suppl):1228S-1230S.
16. Johnston CS, Cartee GD, Haskell BE. Effect of ascorbic acid nutriture on protein-bound hydroxyproline in guinea pig plasma. J Nutr. 1985;115(8):1089-1093.
17. Johnston CS, Kolb WP, Haskell BE. The effect of vitamin C nutriture on complement component C1q concentrations in guinea pig plasma. J Nutr. 1987;117(4):764-768.
18. Dahl H, Degre M. The effect of ascorbic acid on production of human interferon and the antiviral activity in vitro. Acta Pathol Microbiol Scand B. 1976;84B(5):280-284.
19. Sasazuki S, Sasaki S, Tsubono Y, Okubo S, Hayashi M, Tsugane S. Effect of vitamin C on common cold: randomized controlled trial. Eur J Clin Nutr. 2006;60(1):9-17.
20. .S. Department of Agriculture, Agricultural Research Service. USDA National Nutrient Database for Standard Reference, Release 22. 2009. Available at: http://www.nal.usda.gov/fnic/foodcomp/search/.
21. Higdon J, Drake VJ. Vitamin C.  Linus Pauling Institute, Oregon State University. 2006-2009. Retrieved June 15, 2011 from http://lpi.oregonstate.edu/infocenter/vitamins/vitaminC/index.html#lpi_recommend.