A high intake of folate (vitamin B9) from dietary and supplement sources may decrease the risk of Alzheimer's disease, according to a new study published in the Archives of Neurology (2007, vol. 64, no. 1).

Unfortunately, folate levels in young American women are now dropping, according to another recent study by the Centers for Disease Control and Prevention (Morbidity and Mortality Weekly Report, 2007, vol. 55, no. 51). Although reasons for the drop aren't clear, experts say possible causes include high obesity rates, low-carbohydrate diets, and increased consumption of whole-grain products in lieu of other, folate-fortified carbohydrates. (Whole-grain products are not subject to the mandatory folic acid fortification, which the U.S. government instituted in 1998 largely because of folate's critical role in protecting against birth defects).

For the Alzheimer's study, researchers at Columbia University administered a food frequency questionnaire to 965 subjects (ages 65 and older) who had no signs of dementia. After six years, they found that those with the highest total folate intake had the lowest risk of contracting Alzheimer's.

Folate helps lower levels of homocysteine, an amino acid in the blood. Studies have linked elevated homocysteine levels to an increased risk for Alzheimer's, stroke, and heart disease.

Scientists noted that a decreased risk for Alzheimer's was not associated solely with dietary folate or folate from supplements; the benefit was seen only when the two sources were combined. "The richest sources of dietary folate are deep green leafy vegetables, asparagus, broccoli, whole wheat, and brewer's yeast," says Shari Lieberman, PhD, CNS, FACN, author of The Real Vitamin and Mineral Book (Avery, 2007).