Īntioxidants protect cells from the damaging effects of free radicals, which are molecules that contain an unshared electron. As a result, blood and cellular concentrations of other forms of vitamin E are lower than those of alpha-tocopherol and have been the subjects of less research. The liver preferentially resecretes only alpha-tocopherol via the hepatic alpha-tocopherol transfer protein the liver metabolizes and excretes the other vitamin E forms. Serum concentrations of vitamin E (alpha-tocopherol) depend on the liver, which takes up the nutrient after the various forms are absorbed from the small intestine.

Alpha- (or α-) tocopherol is the only form that is recognized to meet human requirements. Naturally occurring vitamin E exists in eight chemical forms (alpha-, beta-, gamma-, and delta-tocopherol and alpha-, beta-, gamma-, and delta-tocotrienol) that have varying levels of biological activity. 'Vitamin E' is the collective name for a group of fat-soluble compounds with distinctive antioxidant activities. Vitamin E is found naturally in some foods, added to others, and available as a dietary supplement.

For a reader-friendly overview of Vitamin E, see our consumer fact sheet on Vitamin E. This is a fact sheet intended for health professionals.

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