Taking B vitamins won't slow mental decline: study

Taking B vitamins don't prevent Alzheimer's disease, nor would it slow mental decline as we age, according to a large scale research by British scientists.

High levels in the blood of a compound called homocysteine have been found in people with Alzheimer's disease.

Taking vitamin B-12 are known to lower levels of homocysteine in the body, so a "homocysteine hypothesis" assumes that taking B vitamins could reduce the risk of Alzheimer's disease and slow mental decline.

In the new research published on Tuesday in the American Journal of Clinical Nutrition, Oxford University researchers brought together data from 11 randomized clinical trials involving 22,000 people, which compared the effect of B vitamins on cognitive function in older people against placebo.

Participants receiving B vitamins did see a reduction in the levels of homocysteine in their blood by around a quarter.

However, when looking at scores for specific mental processes such as memory, speed or executive function, there was no difference between those on B vitamins and those receiving placebo to a high degree of accuracy.

"Our study draws a line under the debate: B vitamins don't reduce cognitive decline as we age," Dr Robert Clarke of Oxford University, who led the work, said.

He said that about 25-30 percent of the adult population take multi-vitamins, often with the idea that they are also good for the heart or the brain, but the evidence just isn't there.

"Much better is to eat more fruit and vegetables, avoid too much red meat and too many calories, and have a balanced diet," he said.