FRIDAY, Aug. 12, 2005 (HealthDayNews) -- Preventing Alzheimer's disease may be as simple as increasing the amount of the B vitamin called folate that you get from fruits, green vegetables and supplements, researchers suggest in a new study.
According to the study, older people whose folate intake is above the recommended dietary allowance are at a significantly reduced risk of developing Alzheimer's.
However, the researchers cautioned that far more research is needed to establish a link between folate and the possible prevention of the brain-wasting disease. In fact, one previous study found folate encouraging the development of Alzheimer's disease.
This latest study appears in the August issue of the journal Alzheimer's and Dementia.
Experts hypothesize that folate protects against Alzheimer's by reducing blood levels of homocysteine, an amino acid. Homocysteine has already been linked to an increased risk for heart disease.
"There are also links between vascular disease and Alzheimer's disease," said lead author Maria M. Corrada, an assistant adjunct professor of neurology at the University of California, Irvine. "So maybe there is some mechanism so that lowering homocysteine may be beneficial."
Folates are B-vitamin nutrients found in foods such as bananas and oranges, leafy green vegetables, asparagus, broccoli, liver, and many types of beans and peas.
Folate supplements are also recommended for pregnant women to help prevent birth defects that affect the brain and spinal cord, called neural tube defects.
In their study, Corrada and her colleagues collected data on 579 men and women 60 and older who participated in the Baltimore Longitudinal Study of Aging. The people in the study kept track of what they ate and what supplements they took for a week.
During a follow-up period that spanned more than nine years, Corrada's team looked at the number of people who developed Alzheimer's and what differences they had in their diets from those who didn't develop the disease.
Over that period, 57 people developed Alzheimer's. Compared with those who developed the disease, study participants with the highest folate intake reduced their risk of developing Alzheimer's by 55 percent, the researchers found.
This reduced risk was not seen for the other vitamins the researchers looked at, including vitamin C, carotenoids and vitamin B12.
"This may give us some clues about what can be done eventually to prevent Alzheimer's disease," Corrada said. "There may be the possibility that folate may have a causal relationship to Alzheimer's disease."
Despite this finding, Corrada doesn't recommend increasing the amount of folate you take in the hope of reducing your risk of Alzheimer's. "At this point the only recommendation should be: Take what's in a multivitamin," she said. "It's premature to recommend anything higher than that."
One Alzheimer's expert noted that this finding is exactly opposite to the conclusion of another recent study.
"A colleague of mine had the exact opposite finding," said Dr. David A. Bennett, director of the Rush Alzheimer's Disease Center in Chicago. Bennett was referring to a study published in the April issue of the Archives of Neurology.
In that study, researchers found that high folate levels may actually cause cognitive decline, based on data for 3,718 people 65 and older.
"This is the problem with observational studies," Bennett said. "You can get really mixed results from observational studies. Observational trials are intended to lay the groundwork for clinical trials. They are not intended to lay the groundwork for any kind of recommendation."
Bennett added that there is observational evidence that homocysteine is associated with an increased risk of Alzheimer's. "It's a fine theory," he said. "But there's an old saying in this field, which is: for any epidemiologic association, we can come up with a biologically possible hypothesis."
Given the contradictory findings, Bennett believes that clinical trials are needed to settle the question of folate's effects on Alzheimer's.
"There's folate supplements out there and people are being encouraged to take folate for various reasons," he said. "I think we need to take a look at that."
More information
The Alzheimer's Association can tell you more about Alzheimer's disease.
