Combined vitamin E+C supplementation increased resistance to total serum lipid oxidation more effectively than supplementation with vitamin E or vitamin C alone at the 36-month follow-up. A strong database shows that vitamin E and C dietary supplements are safe for the general population. Because these nutrients provide antioxidants and other functions for homeostasis and protection against damage caused by free radicals, supplementation has been intensively studied. Because of the perceived benefits, many people consume amounts of vitamins E and C well in excess of the recommended dietary amounts.
As a safety guideline, the Food and Nutrition Board of the Institute of Medicine has established tolerable maximum intake levels of 1000 mg for vitamin E and 2000 mg for vitamin C in adults. Many clinical trials with these vitamins have involved people with various diseases and a consistent pattern of adverse effects has not been observed with any intake. Numerous studies on vitamin C supplementation have provided no evidence to support safety concerns, except for occasional gastrointestinal discomfort or mild diarrhea as a result of the osmotic effects of unabsorbed amounts of vitamin C. The evidence on bleeding effects and other possible adverse effects from a high intake of vitamin E in humans is not convincing.
Clinical trials have not confirmed evidence of the adverse effects of vitamin C derived from its effects on iron absorption and metabolism. Therefore, from clinical trials, we conclude that vitamin E supplements appear safe for most adults in quantities. No interactions were found between vitamin C and vitamin E. However, this does not necessarily mean that there are no interactions.
