Vitamin C


Vitamin C (ascorbic acid, ah-score-bick ah-syd)


Vitamin C (ascorbic acid) is an essential, water-soluble vitamin. It is well-known for its antioxidant properties and ability to reduce free radicals by donating electrons through reduction reactions. (32) The discovery of vitamin C has been attributed to the treatment of scurvy in sailors and the potato famine in Ireland. (8) Administration of approximately 0.01 grams per day can prevent scurvy. (18). In the North American diet, some of the highest concentrations of vitamin C are present in citrus juices, fruit, and a variety of vegetables. (45)

Main Medical Uses

Evidence exists for the use of vitamin C in the treatment of many conditions. Vitamin C administration has been used in atrial fibrillation, (44) the common cold, (39) complex regional pain syndrome, (1) cardiovascular conditions, (3) gout, (28) osteoarthritis, (25) cataracts, (50) blood pressure regulation, (27) glycemic control, (4) upper respiratory tract infections, (48) and inflammation. (24) It is an adjuvant used to prevent and treat iron deficiencies, (14) and tyrosinemia. (49) There is mixed evidence for its use in physical and exercise performance. (6, 40)

Dosing and Administration

The Recommended Dietary Allowance (RDA) of vitamin C for adults is 75 mg per day for females and 90 mg per day for males. It is recommended that smokers increase their intake by an additional 35 mg per day. The optimal intake for the majority of the adult population, without increasing risk of inadequacy or adverse effects, is 200 mg per day. (18)

For an explanation of the classes of evidence, please see the Rating Scales for Evidence-Based Decision Support.

Adverse Effects

Vitamin C is considered to be safe and tolerable. Exceeding the Tolerable Upper Intake Level (UL) of 2000 mg per day for adults can lead to gastrointestinal disturbances and osmotic diarrhea. The daily UL for children aged 1 to 3 is 400 mg, aged 4 to 8 is 650 mg, and aged 9 to 13 is 1800 mg. (17)


Associated Interactions

Mechanism of Action and Metabolism

The main functions of ascorbic acid occur by substrate reduction. As it donates electrons, ascorbic acid becomes a free but stable, ascorbyl radical. Two molecules of this newly formed radical can then be simultaneously reduced to form ascorbate or oxidized to form dehydroascorbic acid (DHA). (4)

Vitamin C is absorbed by the lumen in the small intestine, as well as by renal tubules through sodium-dependent vitamin C transporters for ascorbate. (31, 43) These transporters are located throughout the body and promote cellular accumulation of ascorbate. Similarly, ascorbate that is oxidized to DHA outside of cells can be transported through GLUT1 and GLUT 3 transporters, which are also widely distributed throughout the body. (40) While renal reabsorption of vitamin C occurs, the precise mechanism of efflux in the kidney is yet to be. (13)

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