Vitamin E is a major nutrient that helps protect cells and cell membranes , among other functions. Vitamin E is a fat-soluble vitamin. Such vitamins are absorbed into the body dissolved in lipids (oily or fatty substances). They are stored in the body in the liver and in fat tissues.
Common food sources of vitamin E include fats, oils , nuts , wheat germ, and seeds . Food manufacturers fortify some foods with vitamin E. Vitamin E is actually a group of eight compounds called tocopherols and tocotrienols. One form, called alpha-tocopherol, is most active in the body. Other forms are used in smaller amounts in special roles. Vitamin E dosages are usually expressed in units called alpha-tocopherol equivalents.
Experts at the United States National Academy of Medicine have established a tolerable upper intake level (UL) of 1000 milligrams of vitamin E per day. The UL represents the upper limit for safe intake of the vitamin.
Function.
In the body, vitamin E functions as an antioxidant , protecting cells from damage by molecules called free radicals. Free radicals are highly reactive molecules derived from oxygen-containing compounds. Vitamin E protects cell membranes and helps protect the surface lining of blood vessels. Vitamin E also functions in the immune system and is involved in cell signaling and gene expression.
Deficiency and excess.
People who lack a particular vitamin can develop a vitamin deficiency disease. Because vitamin E is stored in the body, deficiency is rare and takes 5 to 10 years to develop. Vitamin E deficiency is sometimes seen with diseases of the liver or pancreas that impair the absorption of fats in the intestines. A deficiency of vitamin E results in fragile red blood cells. This condition may cause anemia (a lack of healthy red blood cells) and nerve and muscle damage.
Taking megadoses of vitamins without proper medical supervision can cause adverse health effects. Megadoses are doses many times larger than recommended amounts. Too much vitamin E in the body may interfere with blood clotting, leading to an increased risk of bleeding .
History.
The American researchers Herbert M. Evans and Katherine S. Bishop discovered vitamin E in 1922. They observed that female rats fed a special diet failed to reproduce. They determined that an unknown nutrient was missing from the diet. Evans and Bishop called this missing nutrient “anti-sterility factor.” By 1925, Evans began to call it vitamin E. In 1936, working with the American scientist Gladys A. Emerson, Evans isolated vitamin E from wheat germ and other vegetable oils. In 1938, the Swiss chemist Paul Karrer synthesized vitamin E for the first time.
