Background Information
Vitamin E is known chemically as a lipid-soluble antioxidant. It protects the body from free radicals, substances that can damage cells and tissues. Free radicals are produced by the body's own metabolism and can be generated from exposure to environmental factors such as pollution, cigarette smoke, radiation, and some drugs and pesticides. When free radicals attack cell membranes, they promote a harmful process known as lipid peroxidation. Vitamin E serves as one of the body's first defenders against lipid peroxidation by breaking the free radical chain reaction.
Vitamin E is made up of several substances known as tocopherols. Tocopherols are present in practically every component of the diet, particularly in egg yolk, vegetable oils, and cereals. Eight compounds have been isolated that have vitamin E activity. The most active form is d-a-tocopherol. It should be noted that the Institute of Medicine in publishing the new DRI has redefined vitamin E as only, "naturally occurring form (RRR-) and the other three synthetic 2R-stereoisomer forms (RSR-, RRS-, and RSS-) of a-tocopherol for purposes of establishing the human requirements for vitamin E".

 Effects on Health
High plasma levels of vitamin E, particularly a-tocopherol have been associated with decreased incidence of coronary heart disease, Alxheimer's disease, and prostate and other cancers. Taking vitamin E appears to decrease the risk of developing cataracts and male infertility. It also protects LDL from oxidation.

 Dietary Recommendation
The Dietary Reference Intake for vitamin E is 15 mg/day for both men and women. This is equivalent to 22 International Units (IU) of natural-source vitamin E or 33 IUs of synthetic form. The requirement for vitamin E depends on the type of dietary fat consumed and the presence or absence of other antioxidants. Polyunsaturated fatty acids increase the requirement for vitamin E while antioxidants such as selenium and vitamin C decrease the requirement for vitamin E.
The richest sources of vitamin E are found primarily in polyunsaturated vegetable oils such as soybean, corn, cottonseed, and safflower. Other good sources include dart green leafy vegetables, wheat germ, nuts, and legumes.
The upper limit, based on intake from vitamin supplements, is 1,000 mg of tocopherol per day for adults. According to the National Academy of Sciences, persons who consume more than this amount may be at risk of hemorrhagic damage because vitamin E can act as an anticoagulant.

 Effects on Performance
During exercise, particularly strenuous and exhaustive exercise as well as unaccustomed exercise, oxygen consumption may rise several fold. This increase in oxygen consumption has been associated with oxidative damage and muscle injury.
Studies suggest that vitamin E supplementation does reduce oxidative stress and rates of lipid peroxidation and that vitamin E requirements may increase with exercise. Lipid peroxidation is increased following exercise, as measured by increased amounts of exhaled pentane, and vitamin E supplementation reduces this increased lipid peroxidation (Singh, 1992). Vitamin E may reduce the amount of membrane damage following exercise in untrained subjects but there is little evidence showing that vitamin E benefits high-performance athletes. The majority of well-controlled studies have reported no ergogenic effect on physical performance from vitamin E supplementation, except perhaps in athletes exercising at high altitudes.