A lack of folic acid may increase the risk of Alzheimer's disease, according to researchers at the National Institute on Aging Gerontology Research Center in Baltimore, Maryland.

Recent studies have shown that persons with low folic acid levels and elevated homocysteine levels are at an increased risk of developing Alzheimer's disease. Folic acid has been shown to lower homocysteine levels.

Investigators compared the effects of a low folic acid diet on mice bred to develop Alzheimer's-related brain deposits. The low folic acid diet increased homocysteine levels more than 10-fold and led to a substantial loss of neurons.

Normal mice fed the low-folate diet did not show a loss of neurons, the researchers reported in the Journal of Neuroscience.

Researchers concluded that a diet low in folic acid and too much homocysteine makes the brain's neurons become vulnerable to amyloid beta peptides, which cause the plaques linked to the development of Alzheimer's disease.

"Our data suggest that folic acid deficiency and homocysteine impair DNA repair in neurons, which sensitizes them to oxidative damage induced by amyloidB-peptide," concluded the researchers.

Investigators suggest that maintaining a sufficient intake of folic acid will help to keep brain cells healthy and possibly protect against Alzheimer's disease. Folic acid is found in green, leafy vegetables, citrus fruits and juices, whole wheat bread and dried beans.

A daily supplement containing 400 micrograms would normally be sufficient.

Other sources: Journal of Neuroscience