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Alzheimer's Disease Health Center

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Low Levels of B Vitamin Linked to Alzheimer's Lesions


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.
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