During a nine-year study, researchers showed that older adults whose diets were high in folate reduced their risk of Alzheimer's disease by half compared with those whose diets contain less than the Recommended Dietary Allowances (RDA).
The study appears in the inaugural issue of Alzheimer's and Dementia: the Journal of the Alzheimer's Association.
Alzheimer's disease is a progressive brain disorder that gradually destroys memory and the ability to think and reason. An estimated 4 million people in the U.S. have dementia, most with Alzheimer's disease. By 2050, that number could be as high as 16 million, according to the Alzheimer's Association.
More Folate Needed
Using information gathered from the Baltimore Longitudinal Study of Aging, researchers identified the relationship between diet and Alzheimer's disease risk.
They analyzed the diets of 579 volunteers (359 men, 220 women) 60 and older without Alzheimer's disease and followed them for nine years. The researchers looked at what percentage of participants' diets contained antioxidant vitamins (E, C, carotenoids) and B vitamins (folate, B-6, and B-12).
Between 1984 and 1991, participants provided diaries describing their diet during a typical week. Total daily nutrient intake was estimated as the combined intake from diet and supplements.
Healthy Diet Important
Folate has also been shown to lower blood levels of homocysteine, a risk factor for heart disease. High homocysteine levels, as well as decreased folate and vitamin B-12 levels, have also been associated with stroke and Alzheimer's disease.
Foods rich in folate include oranges and bananas, leafy green vegetables, asparagus, broccoli, liver, and many types of beans and peas, as well as fortified bread.
During the follow-up period 57 participants developed Alzheimer's disease.
The researchers then compared the nutrient intake of those who developed Alzheimer's disease with that of those who did not develop the disease. They show that those with a higher dietary intake of folate had an almost 60 percent lower rate of the disease.
They concluded that older adults whose total folate intake (diet and supplement) equaled or exceeded the 400 microgram RDA reduced their chances of developing Alzheimer's disease by 55 percent.
No association was seen between intakes of vitamin C, carotenoids, or vitamin B-12.
When analyzed separately a reduced risk of Alzheimer's disease was seen among people taking "at or above" the RDA for vitamin E or vitamin B-6; however, the protective effects of these vitamins disappeared when folate, vitamin E, and vitamin B-6 were all taken into account together.
"Although folates appear to be more beneficial than other nutrients, the primary message of our study should be that overall healthy diets seem to have an impact on limiting Alzheimer's disease risk," says Maria Corrada, assistant professor of neurology at the University of California in Irvine, in a news release.
Sources: News release, Alzheimer's Association. Maria Corrada, assistant professor of neurology, University of California, Irvine. News release, American Heart Association. Alzheimer's Society. Linus Pauling Institute.
By Patti Connor
Reviewed by Brunilda Nazario, MD
© 2005, WebMD Inc. All rights reserved