B vitamins may slow the advance of Alzheimer's - New Scientist

Those at risk of developing Alzheimer's may be able to slow its onset through daily B vitamins.

We already know that a high level of the amino acid homocysteine in the blood is a risk factor for Alzheimer's, and that B vitamin supplements help reduce homocysteine levels. But it was unclear whether or not these supplements would slow the progression of mild cognitive impairment (MCI) to Alzheimer's.

David Smith and Gwenaëlle Douaud at the University of Oxford led a research effort to find out. They used MRI to track changes in the brains of 200 elderly volunteers with MCI over two years. During this time, half were given high doses of vitamin B12, B6 and folic acid – 300, 20 and 4 times the UK guideline daily amounts, respectively. The rest took a placebo.

In 2010, Smith and his colleagues showed that high doses of B vitamins slowed whole-brain shrinkage by up to 53 per cent in patients with above average homocysteine levels. Now Smith and Douaud's team have looked deeper to work out which brain regions are best protected.

Better function

They found that it was the areas of the brain most seriously affected by Alzheimer's, including the hippocampus and cerebellum, that were protected in volunteers given the vitamins. For instance, in those with high homocysteine, the atrophy rate in these brain regions was 5.2 per cent in the placebo group but just 0.6 per cent in the vitamin group.

The reduction of atrophy seemed to translate into better brain function too: those given B vitamins performed better on cognitive tests.

"It demonstrates for the very first time that it is possible to modify the disease process in Alzheimer's," says Smith.

Simon Ridley at Alzheimer's Research UK cautions that more work is needed to explore the link. "It's important to note the effects in this trial were only seen in a subgroup of people with MCI," he says. "We must also remember that only a proportion of people with MCI will go on to develop Alzheimer's, and it's not yet clear why this is the case."

Bite the bullet

But Smith points out that performing that additional work will take time. He says that since vitamin supplements are safe for most people they could perhaps be offered to high-risk people as a precaution.

"I think we need to bite the bullet and say, is there any reason that elderly people with memory problems shouldn't be offered them in the meantime?" he says.

In fact, he adds, some doctors are already providing B vitamins. "I raised the same question at a conference last year and a psychiatrist in the audience put his hand up and said 'We already do since your first paper came out'. So there's nothing to stop clinicians doing this."

Journal reference: PNAS , DOI: 10.1073/pnas.1301816110

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