Older people who got lots of folate, a nutrient found in leafy green vegetables such as spinach and in fruits such as strawberries, appear to reduce their risk of developing Alzheimer's by more than half, researchers have found — and the findings, if confirmed by more studies, could lead to a relatively simple way to avoid Alzheimer's, an incurable brain disease that afflicts 4.5 million Americans.

"If you could reduce the risk of Alzheimer's by half that would be a huge accomplishment," says William Thies, a spokesman for the Chicago-based Alzheimer's Association. He says there is currently no preventive therapy for this disease, which causes memory loss and confusion.

The study was reported in the first issue of the journal Alzheimer's & Dementia. It's the largest to date to show that folate, a type of B vitamin, could prevent Alzheimer's.

Folate reduces blood levels of homocysteine, a substance that when elevated may damage brain cells and lead to Alzheimer's, says Paul Aisen, a neurologist at the Georgetown University Medical Center in Washington, D.C.

This study doesn't prove that folate reduces the risk of Alzheimer's, so Aisen does not recommend taking a folate supplement.

Still, people can't go wrong by including more fruits and vegetables in their diets, Thies says. Foods rich in folate include whole-wheat bread, oranges, broccoli, spinach and bananas.

Researchers found that people who reported getting at or above 400 micrograms of folate per day, the recommended daily allowance of this vitamin, had a 55 percent lower risk for Alzheimer's than people getting less than that amount. And most people in the study got to that level of folate consumption by taking a supplement.

However, the study collected dietary information in 1998, before wide-scale folate supplementation of breads, cereals, pastas and other grain products. Folate was added to the food supply to help prevent certain birth defects.

Epidemiologist Maria Corrada of the University of California-Irvine and her colleagues collected dietary information from 579 people 60 and older who showed no sign of Alzheimer's. The recruits kept track of the food they consumed and told the researchers if they were taking vitamin supplements that contained folic acid, the synthetic form of folate.

The researchers calculated the total amount of folate consumed and kept track of the recruits for about 10 years. During that time, 57 people developed Alzheimer's.