According to a new study large daily doses of B vitamins could halve the rate of brain shrinkage in elderly people with warning signs of Alzheimer's, potentially delaying the onset of the disease.
Brain shrinkage, a natural part of ageing, happens faster in people with mild cognitive impairment (MCI), a precursor to Alzheimer's and other forms of dementia.
The team of British-led scientists behind the study believe the vitamin treatment could delay or even prevent development of the disease but stressed more research was needed to test this theory.
Over a two-year period, half were given a daily tablet containing high doses of the B vitamins folate, B6 and B12. The rest received a placebo pill with no active ingredients.
The trial, led by researchers at Oxford University assisted by colleagues in Norway, yielded dramatic results.
On average, taking B vitamins slowed the rate of brain atrophy by 30 percent. In some cases, there were reductions as high as 53 percent.
"This is a very striking, dramatic result. It's much more than we could have predicted," said David Smith, one of the study leaders from the Department of Pharmacology at Oxford University,
"It is our hope that this simple and safe treatment will delay the development of Alzheimer's disease in many people who suffer from mild memory problems."
An estimated 37 million people worldwide live with dementia, with Alzheimer's disease causing the majority of cases, according to the World Health Organisation.
Symptoms of MCI include lapses in memory and language problems that are not serious enough to affect daily life. But half of people with the condition develop dementia within five years.
People over the age of 60 without MCI normally experience brain shrinkage of a rate of around 0.5 percent a year.
It is normally twice as fast in people with MCI, and those with Alzheimer's can see their brain lose 2.5 percent of its volume each year.
The doses of B vitamins in the trail were much higher than would be found in a normal diet or health supplements, the scientists stressed.
Smith cautioned people should not rush out and start taking huge doses of B vitamins as the long-term effects were not known.