Experts have cast doubts on a new study, which says that vitamin B could prove to be a revolutionary weapon against Alzheimer's disease.

David Smith and colleagues at the University of Oxford say that high doses of B vitamins may halve the rate of brain shrinkage in older people experiencing some of the warning signs of the disease.

The team instructed a group of 168 people over the age of 70 with mild cognitive impairment (MCI) to take a 2 year course of either daily vitamin B supplements or placebo pills.

The vitamins included folic acid, B6 and B12. Each person had an fMRI brain scan at the start and end of the study, in order to compare how their brains had atrophied or shrunk over the period.

While the brains of the placebo group shrunk by an average of 1.08 per cent per year, those taking vitamin B supplements experienced an average atrophy of "only" 0.76 per cent per year.

However, Clive Ballard, director of research at the Alzheimer's Society, said: "Previous studies looking at B vitamins have been very disappointing and we wouldn't want to raise people's expectations yet," reports New Scientist.

Chris Kennard, chair of the Medical Research Council's Neurosciences and Mental Health Board, told the BBC: "We must be cautious when recommending supplements like vitamin B as there re separate health risks if taken in too high doses," Kennard said. (ANI)