Vitamins, Fat-Soluble Health Article

Vitamin E

The link between vitamin-E deficiency and reproductive failure in rats was first discovered in 1922 by Herbert Evans and Katherine Scott Bishop. The chemical name of vitamin E, tocopherol, is derived from toco, meaning "related to childbirth."

Vitamin E comprises a family of eight naturally occurring compounds: four tocopherols and four tocotrienols, of which alpha-tocopherol is the only one to have vitamin-E activity in the human body. It is also the most common form of vitamin E in food. Vitamin E is highly susceptible to destruction by oxygen, metals, light, and deep-fat frying. As a result, prolonged food storage lowers the vitamin-E content of food.

As with other fat-soluble vitamins, absorption of vitamin E requires adequate absorption of dietary fat. In addition, the percentage of absorption declines as the amount consumed is increased. Vitamin E is stored mainly in adipose tissue, while some is stored in the muscle. The remaining vitamin E is found in cell membranes in tissue.

Vitamin E is an antioxidant and one of the body's primary defenders against oxidative damage caused by free radicals. Its activity is enhanced by other antioxidants such as vitamin C and the mineral selenium. Vitamin E interrupts free-radical chain reactions by getting oxidized, thus protecting cell membranes from free-radical attack. Scientists have implicated oxidative stress in the development of cancer, arthritis, cataracts, heart disease, and in the process of aging itself. However, it is not yet known whether supplementation with megadoses of vitamin E offers protection against heart disease and cancer beyond that provided by positive dietary and lifestyle changes.

Bibliography

Insel, Paul; Turner, Elaine R.; and Ross, Don (2002). Nutrition. Sudbury, MA: Jones and Bartlett.

Wardlaw, Gordon M.; Hampl, Jeffrey S.; and Disilvestro, Robert A. (2004). Perspectives in Nutrition, 6th edition. New York: McGraw-Hill.

Whitney, Eleanor Noss, and Rolfes, Sharon Rady (2002). Understanding Nutrition, 9th edition. Belmont, CA: Wadsworth/Thomson Learning.