Large daily doses of B vitamins could delay -- or even halt -- the onset of Alzheimer's disease, a study suggested Thursday.

The study found that supplementing the diet with vitamin B could halve the rate of brain shrinkage in elderly people with warning signs of the disease.

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 slow or possibly halt development of the disease but stressed more research was needed to test this theory.

In the research, published in the online journal Public Library of Science ONE, brain atrophy was studied in 168 volunteers over the age of 70 diagnosed with MCI.

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."

Rebecca Wood, chief executive of British charity the Alzheimer's Research Trust which co-funded the study, added the results were "very important."

"The strong findings must inspire an expanded trial to follow people expected to develop Alzheimer's, and we hope for further success," she added.

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 trial 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.

Explore further MRI shows brain atrophy pattern that predicts Alzheimer's

(c) 2010 AFP