Vitamin E is a collective name for a group of fat-soluble vitamins occurring naturally in nuts, oils and green leafy vegetables. While there are eight natural forms of vitamin E, only one — alpha-tocopherol — can be used by the body. Vitamin E is stored in the liver, which releases it into the bloodstream as needed. The compound is an antioxidant, which prevents cell damage and is needed for a healthy immune system. It also helps to dilate blood vessels and to prevent blood clots from forming.

Several studies have found that people who consume more vitamin E have a lower risk of heart disease and cancer. But randomized clinical trials found that vitamin E supplements did not prevent heart attacks or strokes and might increase the rates of heart failure. And other randomized trials found no benefits in preventing cancer either.

Vitamin E supplements were also tested for the prevention of cognitive decline, such as dementia or Alzheimer’s disease, but results have been inconclusive. People with higher intakes of vitamin E tended to have lower rates of macular degeneration and cataracts, but supplements have not proven to be effective in preventing those eye disorders.

Vitamin E can interact with various medications, including blood thinners, certain cholesterol medications and chemotherapy or radiotherapy treatments. Higher doses of vitamin E can lead to bleeding or interfere with normal clotting.

The safe upper limit for vitamin E has been set at 1,000 mg, but some studies have shown a small increase in the risk of death in people who take supplements of 400 mg per day or more. Vitamin E deficiency is rare, except in people who have trouble digesting fat.

Synthetic vitamin E, listed on product labels with the designation “DL,” is only half as active as naturally occurring vitamin E, designated with a “D.” As a result, you need twice as much of the supplement to reach the same amount of the nutrient. Most vitamin E supplements contain at least 45 mg of alpha-tocopherol and many contain 180 mg.

Daily recommended amount:Adults: 15 mgLactating women: 19 mgChildren (0-6 months): 4 mgChildren (7-12 months): 5 mgChildren (1-3 years): 6 mgChildren (4-8 years): 7 mgChildren (9-13 years): 11 mgChildren (14-18): 15 mg

Good sources:Almonds (dry roasted, 1 oz.): 7.4 mgSunflower oil (1 TBS): 5.6 mgPeanut butter (2 TBS): 2.9 mgBroccoli (cooked, 1 cup): 1.2 mgFortified breakfast cereal (1 cup): 20 to 40 mg

Sources: National Institutes of Health, University of Florida

— Markian Hawryluk, The Bulletin