Am J Clin Nutr. 2005;81(4):736-45.
Vitamins E and C are safe across a broad range of intakes.
Hathcock JN, Azzi A, Blumberg J, Bray T, Dickinson A, Frei B,
Jialal I, Johnston CS, Kelly FJ, Kraemer K, Packer L, Parthasarathy S, Sies H,
Traber MG.
Council for Responsible Nutrition, Washington, DC, USA.
jhathcock@crnusa.org
A robust database shows that dietary supplements of vitamins E and C are safe
for the general population. Because these nutrients supply antioxidant and
other functions for homeostasis and protection against free radical damage,
supplementation has been intensively studied. Because of perceived benefits,
many persons consume quantities of vitamins E and C well above the recommended
dietary allowances. As safety guidance, tolerable upper intake levels have been
established by the Food and Nutrition Board, Institute of Medicine, at 1000 mg
for vitamin E and 2000 mg for vitamin C in adults. Many clinical trials with
these vitamins have involved subjects with various diseases, and no consistent
pattern of adverse effects has occurred at any intake. Numerous studies of
vitamin C supplementation have provided no pattern of evidence to support
concerns about safety other than occasional gastrointestinal upset or mild
diarrhea resulting from the osmotic effects of unabsorbed quantities of vitamin
C. Evidence of bleeding effects and other potential adverse effects of high
vitamin E intakes in humans is not convincing. Evidence of adverse effects of
vitamin C that result from its effects on iron absorption and metabolism has
not been confirmed in clinical trials. Thus, we conclude from clinical trial
evidence that vitamin E supplements appear safe for most adults in amounts
</=1600 IU (1073 mg RRR-alpha-tocopherol or the molar equivalent of its
esters) and that vitamin C supplements of </=2000 mg/d are safe for most
adults.