Dr. David Smith of Oxford University in England said the amino acid homocysteine is linked to shrinkage of the brain. Shrinkage of the brain is linked to Alzheimer's disease.
Previous studies show patients with mild cognitive impairment, a precursor to Alzheimer's disease, suffered 50 percent less brain shrinkage overall if they took vitamin B supplements.
The current study of 156 patients, published in the Proceedings of the National Academy of Sciences journal, found brain shrinkage was reduced by 90 percent in particular areas of the brain most vulnerable in Alzheimer's patients, the Daily Telegraph reported.
"It is too early to know whether these effects mean someone is less likely to develop dementia," Dr. Eric Karran, director of research at Alzheimer's Research UK, said in a statement. "It is also not clear from other research in this area whether B vitamins would have any benefit for those who already have dementia."