Vitamin E is a fat-soluble vitamin. It has important antioxidant properties. There are several forms of vitamin E. Alpha-tocopherol is the most active form in humans. It protects the body's cells from the actions of free radicals (oxidants), which are the waste products of energy metabolism. Free radicals can damage body cells through oxidation and increase the risk of heart disease and cancer. It has been theorized that vitamin E may reduce the incidence of heart disease and cancer through its antioxidant effects. Studies evaluating the effect of vitamin E supplementation have been contradictory. More studies are needed to fully evaluate the ability of vitamin E to reduce heart disease and cancer. Foods that contain vitamin E are nuts, oils, green leafy vegetables and fortified cereals. The recommended daily allowance (RDA) for vitamin E is 22.5 IU (international units) per day for men and women 14 years of age and older. Little information is known regarding excessive supplementation with vitamin E. However, due to the potential for blood thinning activity, following the RDA for vitamin E is recommended.