Vitamin B12 and folic acid supplements may not decrease the risk of memory problems and Alzheimer’s disease in older adults, even if they have high homocysteine levels.

Vitamin B12 and folic acid may not offer the kind of brain boost to seniors suggested by earlier research. In a new, larger study, scientists from the Netherlands found that people taking these supplements for two years had no significant improvement in cognitive performance.

Earlier observational studies hinted at the benefits of folic acid and vitamin B12 for preventing dementia and Alzheimer’s, prompting interest in using these compounds to improve brain function. Later randomized, controlled trials, however, were less convincing.

“The idea that a naturally occurring vitamin can fuel brain power is an exciting entity,” said Dr. Jessica L. Zwerling, a neurologist and associate director of the Montefiore Einstein Center for the Aging Brain and who was not involved in the study.

The brain benefits of these supplements were thought to stem from their ability to lower blood levels of homocysteine, an amino acid that, in high levels, has been linked to memory loss and dementia.

The current study, one of the largest to test the long-term use of these supplements on memory and thinking skills, was designed to provide a clearer picture.

“Since homocysteine levels can be lowered with folic acid and vitamin B12 supplements, the hope has been that taking these vitamins could also reduce the risk of memory loss and Alzheimer’s disease,” said study author Rosalie Dhonukshe-Rutten, a nutritional scientist at Wageningen University in the Netherlands, in a press release.

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The study, published online yesterday in the journal Neurology, included more that 2,900 healthy senior men and women, with an average age of 74 and high blood levels of homocysteine.

Volunteers were randomly assigned to take either a tablet containing 500 micrograms of vitamin B12 and 400 micrograms of folic acid, or a placebo pill without those vitamins, every day throughout the two years of the study. To assess brain function, researchers gave volunteers a variety of memory and thinking tests at the start and end of the study.

“While the homocysteine levels decreased by more in the group taking the B vitamins than in the group taking the placebo, unfortunately there was no difference between the two groups in the scores on the thinking and memory tests,” said Dhonukshe-Rutten.

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Previous research included another two-year study, published in 2010 in Neurology, that found that vitamin B12, vitamin B6, and folic acid supplements did not improve the mental abilities of men 75 and older. Eight years after the study ended, though, the men had a small decrease in their risk of cognitive impairment, though it was not a significant change.

Certain people taking the supplements in the new long-term study did experience some small positive effects. One analysis of the data found that people with low blood levels of holotranscobalamin, the active form of vitamin B12, improved their thinking speed with the vitamin B12 and folic acid supplements.

“This agrees with the entire clinical picture of B12-related to memory trouble,” said Zwerling.

The supplements given to both groups in the new study also included 15 micrograms of vitamin D3, which may improve brain function at high levels. It is possible that vitamin D3 diluted the effects of the other supplements on mental performance, although it could have simply eliminated any vitamin D3 deficiency among the participants.

“Individuals, especially the elderly, differ in their metabolism of vitamin D and susceptibility to vitamin D deficiency,” said Zwerling. “Overall, the use of D3 just ‘evened the playing ground’ in a population known to have high rates of deficiency.”

Although this new study failed to demonstrate the mental benefits of vitamin B12 and folic acid supplements, vitamin B12 remains essential for overall health.

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“B12 is an important vitamin both for the central and peripheral nervous systems,” said Zwerling. “A B12 deficiency presents in many ways: it can present as hand numbness, distal foot numbness, cognitive changes, gait instability.”

People concerned about their vitamin B12 levels should check with their doctor, since other health issues can mimic a vitamin deficiency.

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