Folate may reduce risk of Alzheimer's disease

By Anthony J. Brown, MD

NEW YORK (Reuters Health) - The findings from a longitudinal study indicate there is an inverse association between folate intake and the risk of Alzheimer's disease. More clinical trials are needed, however, before increasing folate intake can be recommended as a means of preventing Alzheimer's disease.

Folate is a water-soluble form of vitamin B necessary for the formation and maintenance of new cells.

There is evidence that elevated levels of homocysteine -- an amino acid, molecules considered to be the "building blocks" of proteins -- may raise the risk of Alzheimer's disease, Dr. Jose A. Luchsinger, from Columbia University Medical Center in New York, told Reuters Health.

"Because folate and vitamin B12 work in one pathway to decrease homocysteine levels and vitamin B6 works in another, they might have an effect on the risk of Alzheimer's disease."

In their study, reported in the Archives of Neurology, the researchers assessed the occurrence of Alzheimer's disease in 965 dementia-free older adults who completed a food frequency questionnaire and were then followed for an average of 6.1 years. Dietary and supplemental folate, vitamin B6, and vitamin B12 intake were estimated based on the questionnaire responses.

A total of 192 subjects were diagnosed with Alzheimer's disease during follow-up. When the subjects were stratified into four groups based on amount of folate intake, those with the highest 25 percent were 50 percent less likely to develop Alzheimer's disease than those with the lowest 25 percent.

By contrast, levels of vitamin B6 and B12 were not associated with the risk of Alzheimer's disease, the authors note.

Interestingly, high folate intake was only "modestly associated with lower homocysteine levels," Luchsinger noted, "suggesting that other mechanisms may be involved" in the possible anti-Alzheimer's effect.

Luchsinger said that additional clinical trials are currently underway that should help clarify the effect of folate intake on the risk of Alzheimer's disease. He also noted that his group is presently involved in a larger observational study examining the association.

SOURCE: Archives of Neurology, January 2007.