vitamin E, any or all of the group of fat-soluble vitamins that consist of the tocopherols and are essential for normal reproduction, muscle development, resistance of erythrocytes to hemolysis, and various other biochemical functions. It is a fat-soluble antioxidant and acts in maintaining the stability of polyunsaturated fatty acids and other fatlike substances, including vitamin A and hormones of the pituitary, adrenal, and sex glands. Deficiency is rare and may take from months to years to occur but results in muscle degeneration, vascular system abnormalities, megaloblastic anemia, hemolytic anemia, infertility, creatinuria, and liver and kidney damage and is associated with the aging process. The richest dietary sources are wheat germ; soybean, cotton seed, peanut, and corn oils; margarine; whole raw seeds and nuts; soybeans; eggs; butter; liver; sweet potatoes; and the leaves of many vegetables, such as turnip greens. It is stored in the body for long periods of time so that any deficiency is rare. It is considered nontoxic except in hypertensive patients and those with chronic rheumatic heart disease. Alpha-tocopherol is the most physiologically active form of the group. Toxicity is also rare. Also called alpha-tocopherol, tocopherol.