Taking B vitamins doesn't slow mental decline as we age, nor is it likely to prevent Alzheimer's disease, conclude researchers who have assembled all the best clinical trial data involving 22,000 people to offer a final answer on this debate. When looking at measures of global cognitive function -- or 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.

Source: Taking B vitamins won't prevent Alzheimer's disease, researchers conclude