Alzheimer's Disease Health Center

Low Levels of B Vitamin Linked to Alzheimer's Lesions

April 4, 2000 (New York) -- Low blood levels of the B vitamin folic acid may play a role in increasing a woman's risk of developing Alzheimer's disease as she ages, according to a study of Catholic nuns.

The unusual study, reported in the April issue of the American Journal of Clinical Nutrition, found that nuns who had the lowest levels of folic acid in their blood had more Alzheimer's-like brain lesions when they died than their fellow sisters who had higher levels.

Folic acid is known to be important to brain development. In pregnant women, insufficient folic acid can cause serious neurological problems in babies, such as spina bifida, the incomplete formation of the spine. Folic acid supplements are recommended for all women of childbearing age to minimize the risk.

While the new study is not proof that similar supplementation in elderly women or men will decrease their risk of developing Alzheimer's in their old age, it suggests that folic acid may play an ongoing role in protecting the brain throughout our lifetimes, say study author David A. Snowdon, MD, and colleagues from the Sanders-Brown Center on Aging at the College of Medicine of the University of Kentucky in Lexington.

Snowdon studied 30 nuns from the order of the School Sisters of Notre Dame, who provided blood samples and underwent testing of their mental abilities when they were 78 to 99 years of age. The nuns also gave permission to be autopsied after death.

In the autopsies, more than 50% of the sisters were found to have varying degrees of atrophy, or wasting away, of a major area of the brain. Half had significant numbers of the brain lesions that have been associated with Alzheimer's disease.

Extensive examination of the nuns' blood for indications of their nutritional status found that the only difference between sisters with brain wasting and those without was the level of folic acid. Those with the lowest folic acid levels had the greatest degree of brain wasting. Among nuns with the Alzheimer's-like lesions in their brains, there was a higher degree of mental decline.

The mechanisms by which low folate levels may cause brain wasting or Alzheimer's lesions are unclear, but in the body, folic acid reduces blood levels of an amino acid known as homocysteine. Studies have shown that if homocysteine builds up in the blood, it may cause blood-vessel disease.

In an editorial accompanying the study, Irish researchers say the findings add to the evidence that changes in the way folic acid is metabolized as we age may accelerate the development of brain-wasting conditions such as Alzheimer's disease.

But a folate expert who spoke to WebMD about the findings says he believes the study is of little value, because none of the folic acid levels found in the participants' blood were what anyone would consider low.