Two independent studies have provided the first strong evidence that people who eat diets rich in Vitamin E might reduce their risk of getting Alzheimer's, a crippling brain disease.

The apparent benefits, reported today by researchers in Chicago and in the Dutch city of Rotterdam, were seen in people who consumed foods such as grains, nuts, milk, vegetable oils, egg yolks and poultry - natural sources of the antioxidant vitamin.

"These were the first studies to show a direct link between dietary intake of Vitamin E and the development of Alzheimer's disease," said Dr. Martha Clare Morris, principal investigator at Rush-Presbyterian-St. Luke's Medical Center in Chicago.

In both studies, she said, "the more Vitamin E participants consumed, the lower their risk."

Oddly, a reduced risk was not observed in people who took Vitamin E supplements, which provide higher doses of the compound than most people can obtain from food.

The studies, published in today's Journal of the American Medical Association, tested a hypothesis that for years has intrigued scientists eager to find ways of preventing a heartbreaking disease that strikes increasing numbers of people each year as societies age.

Alzheimer's is a progressive brain disease that robs people of memory, speech, reasoning and the ability to accomplish simple tasks and recognize people who were familiar. In the United States, an estimated 360,000 people annually are diagnosed with the disease, though the number is expected to triple in the next 40 years.

The risk of developing Alzheimer's increases as a person ages. For people 65 and older, the risk is about 5 percent. For those 85 and older, the risk is greater than 20 percent.

Antioxidants are a class of chemicals that counteract naturally occurring compounds known as free radicals, which have been implicated in Alzheimer's. Free radicals are released when a cell dies and are poisonous to nearby cells.

Scientists were quick to explain that the new findings, while advancing the idea that antioxidants might protect the brain, do not settle the issue.

"Clearly, the results from these studies and others are not necessarily conclusive," said Dr. Neil Buckholtz, who heads dementia research at the National Institute on Aging, which funded the Chicago study.

But Dr. Constantine G. Lyketsos, an Alzheimer's researcher at the Johns Hopkins School of Medicine, said the reports are tantalizing because they suggest a possible way of preventing the disease years before the first symptoms arise.

"I think most people in my shoes are persuaded that the brain degeneration of Alzheimer's disease is happening 10 to 20 years before the symptoms," he said. "If that's true, then the best strategy to manage the symptoms is to prevent them."

The studies had important similarities and differences.

In Chicago, scientists at Rush-Presbyterian recruited 815 men and women 65 and older and followed them for an average of 3.9 years. In the Netherlands, researchers with the Erasmus Medical Center studied 5,395 men and women 55 and older and tracked them for about six years.

In both studies, researchers asked participants what they ate and monitored them to see how many developed symptoms of Alzheimer's.

While the Dutch study found lower rates of Alzheimer's among people who ate diets rich in Vitamin A and Vitamin C, the Chicago study did not see a benefit from Vitamin C. Both vitamins have antioxidant properties.

Researchers in Chicago divided participants into five levels of Vitamin E consumption. People in the group that consumed the most Vitamin E had a 70 percent lower risk of Alzheimer's than people who got the least. In Rotterdam, researchers divided participants into three groups. Those who consumed the most had a 40 percent lower risk than those getting the least.

Christine Tangney, a nutritionist at Rush-Presbyterian, said it was impossible to come up with a dietary prescription. But she noted that the people whose risk was lowest did not eat extraordinary amounts of foods rich in the Vitamin E.

The lowest-risk people consumed between 10 and 40 international units of Vitamin E, far less than the 400 units contained in many dietary supplements. (An international unit is a standard measure of potency.)

Why supplements did not offer the same benefits was unclear, though scientists offered a few possible explanations. Many of the people on supplements had only recently begun taking them - and perhaps not enough time has passed to achieve an effect.

Also, supplements contain a synthetic form of Vitamin E that might be less effective in preventing Alzheimer's.