Seniors' Health: Folic acid may lower risk for Alzheimer's disease

High intake of folic acid from a combination of food and supplements may decrease the chances of developing Alzheimer's disease.

Dr. José Luchsinger and his colleagues at Columbia University in New York followed the diets of 965 adults age 65 and older for an average of six years. The researchers used food questionnaires to estimate the participants' consumption of folic acid, a B vitamin, as well as vitamins B6 and B12.

All participants were free of Alzheimer's disease and other forms of dementia at the beginning of the study, but 192 cases of Alzheimer's disease developed during the study period. The group with the highest intake of folic acid from all sources was significantly less likely to develop Alzheimer's than the group with the lowest intake.

However, folic acid from food or supplements alone did not have a significant impact on Alzheimer's disease risk. Nor were intakes of vitamins B6 and B12 linked to risk of Alzheimer's disease.

One possible basis for the apparent link between high intake of folic acid and decreased Alzheimer's risk is the relationship between the vitamin and homocysteine, an amino acid in the blood. "There have been a few papers that reported that high homocysteine levels are related to a higher risk of Alzheimer's disease," Luchsinger says.

Supplementation with folic acid, vitamin B6 and vitamin B12 has been shown to decrease homocysteine levels, but Luchsinger says his study results have made him wonder if folic acid affects Alzheimer's disease risk through channels other than homocysteine.

"The homocysteine effect in our data was not particularly strong," he says. "The folate effect is certainly stronger than the homocysteine effect and ... whatever happened in our data was specific to folate, and not the other homocysteine-related vitamins B6 and B12."

Food sources of folic acid include enriched grain products such as breakfast cereals, bread, pasta and rice, as well as dark leafy greens and legumes such as lentils and chickpeas.