Vitamin E

Vitamin E is a generic term for several of the tocopherols that have similar activity, and the unit of measure is based on the level of tocopherol with an activity equivalent to that of alpha-tocopherol. Beta-tocopherol has a lower level of activity than alpha-tocopherol so more of it would be necessary for the same effect. The adult DRI for vitamin E is 15 milligrams per day, a level easily obtained by consuming green leafy vegetables, vegetable oils, seeds, nuts, liver, and corn. However, a failure to consume sufficient vegetables, nuts, or vegetable oil may place adults at risk of an inadequate intake. It is difficult to induce a vitamin E deficiency in humans, and it also appears to be a relatively nontoxic vitamin (there is no evidence of toxicity from consuming the vitamins from food). The Institute of Medicine indicates that adverse effects from vitamin E supplementation may include hemorrhagic toxicity.

Vitamin E is a potent antioxidant that protects membranes from destruction by peroxides. Peroxides are formed when fats (especially polyunsaturated fats) become oxidized (rancid). These peroxides are called free radicals because they bounce around unpredictably inside cells, altering or destroying them. Since vitamin E is an anti oxidant, it helps capture oxygen, thereby limiting the oxidation of fats to protect cells.

Several studies on vitamin E and physical performance have been conducted, but none has found an improvement in either strength or endurance with vitamin E supplementation. Studies evaluating whether vitamin E supplementation reduces exercise-induced peroxide damage have mixed results. Some suggest that a clear reduction in peroxidative damage occurs, but others have found that vitamin E has no benefit. It seems clear that more information on vitamin E is needed before a definitive exercise-related benefit can be claimed. However, the theoretical basis related to a reduction in peroxidative damage through a slight increase in additional vitamin E consumption is sound. Vitamin E supplements may be sold in international units (IU). One milligram of alpha-tocopherol is equivalent to approximately 1.5 IU of vitamin E.