Vitamin E is an antioxidant that helps protect cells from damage caused by free radicals. These are unstable molecules with missing electrons that form when cells burn oxygen. Adequate levels of vitamin E are necessary for proper functioning of the reproductive system, nerves and muscles.

Vitamin E’s antioxidant properties also prevent the oxidation of low-density lipoprotein (LDL) cholesterol, the so-called “bad” cholesterol. This may lower the risk of heart disease and stroke.

Vegetable oils are the best source of vitamin E. These include oils made of soybean, corn, canola, sunflower, cottonseed and safflower. Foods made of oil such as certain types of margarine and salad dressings are good sources of vitamin E. Experts usually recommend that people get all of their vitamin E from their diets rather than from supplements. However, in some cases supplementation may be advised.

Deficiency of vitamin E is rare but may occur in premature babies with very low birth weights. It also may occur in people who have conditions that are associated with poor fat absorption, such as cystic fibrosis and Crohn's disease. Vitamin E deficiency may cause several symptoms, including leaving people more vulnerable to damage caused by free radicals.

Excessive levels of dietary vitamin E do not appear to pose health problems. However, taking high levels of a vitamin E supplement does appear to cause health problems, such as impairing the blood-clotting action of vitamin K, leading to an increased risk of bleeding.