Vitamin B12 deficiency linked to memory problems
September 26th, 2011
04:49 PM ET

Vitamin B12 deficiency linked to memory problems

There's been a lot of buzz about vitamin B12 in recent years, and here's another reason to pay attention to it:

A new study finds that a deficiency in vitamin B12 is associated with memory and thinking problems, as well as brain shrinkage. The research is published in the journal Neurology.

Researchers did not prove that low vitamin B12 levels cause these cognitive abnormalities, but they did find a strong association with markers of deficiency, said study co-author Dr. Martha Morris of the Rush University Medical Center in Chicago.

The theory is that adequate levels of vitamin B12 is necessary for the brain's myelin sheath, an insulating layer around nerves. When the sheath gets damaged, impulses between transmitted along nerve cells slow down.

Vitamin B12 is found in meats, fish, shellfish and dairy products, and some cereals are fortified with it. People over 65 in particular may need B12 supplements because older patients' bodies have a harder time absorbing this vitamin.

Researchers looked at 121 participants in the Chicago Health and Aging Project. They looked at both serum levels of vitamin B12 and markers of vitamin B12 deficiency.

The study found that methylmalonate, a marker of vitamin B12 deficiency, is associated with a reduction of brain volume and so may contribute to cognitive problems. Homocysteine, an amino acid associated with low B12 levels as well as folate, was linked to thinking problems through a different mechanism involving abnormal white matter signals (as seen on certain kinds of MRIs).

There aren't a lot of data on using these markers clinically for the purposes of testing the health of older patients, said Dr. James Lah, neurologist at the Emory University School of Medicine in Atlanta, Georgia, who was not involved in the study. The study points to them as potentially helpful, but more research needs to be done, he said.

The study did not find an association between the serum B12 levels of participants and the likelihood of brain problems. Morris said that makes sense because while low levels negatively affect the brain, high levels above normal aren't necessarily better than adequate levels.

"There’s a level we should all have, and if you fall below that, it could cause problems," she said.

Quantifying that level is up for debate, but the National Institutes of Health offers  guidelines for recommended vitamin B12 intake at various ages.

Morris and colleagues did not look at this phenomenon in Alzheimer's patients, but a small 2010 study in Neurology found that people who tended to eat vitamin B12-rich foods are less likely to develop Alzheimer's than those who did not. Vitamin B12 deficiency has not been shown to be directly involved in the pathology of Alzheimer's in the brain, but it may aggravate the brain in other ways that could lead to Alzheimer's. "We can't discount its involvement," Lah said.

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