The analysis of 121 people found that those with lower vitamin B12 levels scored worse on cognitive tests and had smaller brain volumes as revealed by MRI scans. Shrinking brain volume has been linked to dementia in other studies.

"Every single marker of low vitamin B12 was correlated with low brain volume," said study researcher Christine Tangney, a clinical nutritionist at Rush University in Chicago.

Vitamin B12 is found in meat, fish, eggs and dairy products. Deficiency in vitamin B12 is common in those who adhere to a vegan diet and in third-world countries. However, a growing body of evidence suggests that elderly people in developed counties are also at risk of B12 deficiency.

The new results, published in the journal Neurology, suggest that doctors should test vitamin B12 levels when treating anyone with signs of dementia, the researchers said.

"As folks get older, their guts change in their ability to absorb vitamin B12," Tangney told MyHealthNewsDaily. "For many people, the reason is that their stomach acid production is reduced." Acid breaks down the bonds between vitamin B12 and proteins, so older people may need more vitamin B12 as they age, and may be more likely to be deficient in the vitamin, she said.

In a normal brain, vitamin B12 allows cells to form new connections, a process that allows memory formation. B12 is also a vital component of myelin -- the coating that protects many brain cells. These roles of B12 could explain why low levels of the vitamin lead to dementia or memory loss, the researchers said.

In the new study, Tangney and her colleagues measured B12 levels in a group of people who had participated in the Chicago Health and Aging Project, a long-term study of common chronic health problems in the elderly. The team had previously reported finding an association between vitamin B12 levels and performance on cognitive tests in this group. Most recently, they brought 121 of the participants into the lab for further research -- a battery of 17 tests of memory and cognition -- as well as brain MRI scans.

Those with lower vitamin B12 levels scored worse, on average, on the tests. They also had smaller total brain volume, and less white matter, which is mostly made up of the myelin that coats neurons.

David Smith, a neuroscientist at Oxford University who has performed similar studies in the U.K., said that more work is needed to show whether vitamin B12 supplements will treat or prevent some cases of dementia.

"We need further clinical trials to test whether extra B12 vitamins can slow down or prevent the development of Alzheimer's disease," Smith said.

One noteworthy result of the new study, Smith said, was that reduced brain volume and lower cognitive performance were seen in those whose vitamin B12 levels were still above the official cutoff for B12 deficiency.

"This study and others support the fact that we should be asking the question: what is a desirable B12 level in the elderly population?" Smith said. "Do we need to rethink the cutoff value for deficiency?"

For now, Tangney said, doctors and patients should at least be aware of the symptoms of vitamin B12 deficiency, which include not only dementia and memory loss, but tingling in the hands, poor reflexes, poor balance and vision problems.

"The problem is that the everyday family physician is not necessarily always thinking about vitamin B12 when a patient comes into their office with these symptoms," Tangney said. "If, as an older person, you start experiencing problems with memory, it would be smart for you to talk to your physician about whether you're getting enough B12 in your diet and through supplements."

 From the September 28, 2011, Prepared Foods' Daily News.