Vitamin E is a fat-soluble vitamin with antioxidant properties. The term 'vitamin E' actually represents a group of eight different tocopherols, lipid soluble compounds that are synthesized by plants and required by most animals, including humans. Of these, d-alpha-tocopherol is the naturally occurring form with the greatest vitamin activity.
The eight different forms (isomers) of vitamin E are alpha-, beta-, gamma-, and delta-tocopherol; and alpha-, beta-, gamma- and delta-tocotrienol. Alpha-tocopherol is the most active form in humans. Dosing and daily allowance recommendations for vitamin E are often provided in alpha-tocopherol equivalents (ATEs) to account for the different biological activities of the various forms of vitamin E, or in international units (IU), which food and supplement labels may use. The conversion factor is 1 milligram of an ATE=1.5 IU.
Some experts believe that the supplementation of vitamin E in the form of alpha-tocopherol rather than gamma-tocopherol may play a role in the apparent negative effects or lack of effects reported in the literature. Gamma-tocopherol is thought to have more antioxidant effects than alpha-tocopherol. Intake of alpha-tocopherol reduces the level of gamma-tocopherol in the body and therefore may reduce efficacy. Additional research in this area is warranted.
Foods that contain vitamin E include eggs, fortified cereals, fruit, green leafy vegetables (such as spinach), meat, nuts, nut oils, poultry, vegetable oils (corn, cottonseed, safflower, soybean, sunflower), argan oil, olive oil, wheat germ oil and whole grains. Cooking and storage may destroy some of the vitamin E in foods.
Vitamin E has been proposed for the prevention or treatment of numerous health conditions, often based on its antioxidant properties. However, aside from the treatment of vitamin E deficiency (which is rare), there are a lack of clearly proven medicinal uses of vitamin E supplementation beyond the recommended daily allowance. There is ongoing research on its use in numerous diseases, particularly in cancer and heart disease.
For more information about vitamin E, please visit Natural Standard's Foods, Herbs & Supplements Database.