CHICAGO — Moderate supplements of vitamin E, already believed to protect older people from heart disease and dementia, also boost the immune system in people over 65, a new study found.

The research suggests that older people ought to take about 20 times more vitamin E a day than the current recommended daily allowance of 8 to 10 milligrams, authors said.

"We looked at three different levels of vitamin E - 60, 200 and 1300 milligrams, and the 200 milligrams ( 400 I.U. ) seemed to be optimal," said immunologist Simin N. Meydani of the USDA Human Nutiition Research Center on Aging at Tufts University in Boston.

The researchers compared supplements with a placebo among 88 healthy people age 65 and older. They reported the results in Wednesday's issue of the Journal of the American Medical Association.

Daily 200-milligram supplements for four months increased subjects' T-cell function by 65 percent and their response to hepatitis B vaccine sixfold, compared with placebos, researchers said.

T-cells are white blood cells that help fight viruses and tumors and contribute to the body's defenses in other ways. Vaccine response refers to the level of protection that a vaccine provokes in the body.

No adverse effects were reported. Doses of 800 milligrams boosted inununity similarly in those measures and others, but pushed them no higher, Meydani said.

"The problem with a lot of studies in nutrition is that you find something (beneficial), and people think more must be better," Meydani said.

Other studies have indicated that vitamin E supplements can protect against heart disease, cancer and even Alzheirner's disease, apparently by neutralizing destructive molecules known as free radicals, which result from metabolism and disease-fighting activity.