Low Levels of B Vitamin Linked to Alzheimer's Lesions

From the WebMD Archives

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.

Jacob Selhub, PhD, says that if there is a relationship between folic acid levels and Alzheimer's disease, it can only be shown by studying people with folate deficiencies. Without truly low folate levels, he says, there is no support for the theory that homocysteine builds up and destroys blood vessels, paving the way for Alzheimer's disease and dementia. Selhub is with Tufts University's Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging in Boston.

Snowdon says his findings only point to an association between relatively low folic acid levels and brain wasting, and that more study is needed.

"This is some evidence -- though not definitive -- that folic acid may be important in maintenance of the integrity of the nervous system," he tells WebMD. "In this special population, we could see a strong association between folate level and the degree of atrophy. That's all. We were not trying to define normal based on very old Catholic sisters. We were reporting a relationship that is in agreement with other studies, but certainly it needs to be studied in more populations, and we need to learn more about folate and the potential benefits of folate supplementation on a variety of health aspects."

Vital Information:

  • Researchers suspect that folate, a B vitamin, may play an ongoing role of protecting the brain throughout our lifetimes.
  • In a recent study, women with the lowest levels of folate in their blood were more likely to have Alzheimer's-type brain lesions when they died.
  • It is still unclear how folate levels affect the development of brain wasting or Alzheimer's disease.