Supplement Update

Its claim to fame: Vitamin E has been associated with reducing heart disease because it blocks oxidation of LDL (bad) cholesterol, making the cholesterol less likely to cling to artery walls. However, only one out of four large-scale trials of megadoses of vitamin E showed a reduced risk of heart attacks.

Old RDA: Women, 8 milligrams (12 IU). Men, 10 milligrams (15 IU).

New RDA: 15 milligrams (22 IU) of natural vitamin E, also called d-alpha-tocopherol, for adults.

Recommended upper limit: 1,000 mg per day from supplemental sources, for adults 19 and older. (A lower limit is recommended for children.) Anything higher increases your risk of uncontrolled bleeding.

Best food sources: Vegetable oils, such as sunflower and safflower; nuts; and seeds. Smaller amounts of vitamin E are found in dairy foods, eggs, beef, whole grains, fruits, and vegetables.

Supplement notes: Because vitamin E is found in fat, some people may need to meet the RDA by taking a supplement. "If you're eating 3,000 calories a day, it's easy to get your 15 milligrams, so don't worry about it," says Maret Traber, Ph.D., associate professor at the Linus Pauling Institute at Oregon State University and Institute of Medicine panelist. "If you're eating only 1,500 calories a day, you may have trouble getting there. I'd rather see someone take a vitamin E supplement and eat a low-fat, low-calorie diet rich in fruit and vegetables than for the person to eat more fat just to get the vitamin E," Traber says.

When buying the supplement, look for natural vitamin E, also known as d-alpha-tocopherol. Researchers used to think synthetic vitamin E, known as dl-alpha-tocopherol, was just as effective, but it is not, Traber says. Many multivitamins contain synthetic vitamin E, Traber warns, so check labels carefully.