Low levels of vitamin B12 linked to Alzheimer's

People with low levels of vitamin B₁₂ may be at greater risk of developing Alzheimer's disease. The finding supports previous research showing large doses of B vitamins might halve the rate of brain shrinkage.

Babak Hooshmand and colleagues at the Karolinska Institute in Stockholm, Sweden, followed 271 healthy people aged 65 to 79 for seven years. The researchers measured the blood concentration of the amino acid homocysteine, high levels of which have been linked to negative effects on the brain, such as stroke. They also measured levels of active vitamin B₁₂, which can decrease homocysteine levels.

By the end of the study, 17 people had developed Alzheimer's. A level of homocysteine moderately above average corresponded to a 16 per cent higher risk of developing Alzheimer's, while a level of active B₁₂ slightly above average meant a 2 per cent lower risk.

"This is a very convincing study," says David Smith of the University of Oxford, who has investigated the effect of B-vitamin supplements on brain shrinkage. He says it is the first to show that low levels of active vitamin B₁₂ are a risk factor for developing dementia several years later.

Although B₁₂ deficiency is common among elderly people, more evidence is needed before recommending B₁₂ supplements to stave off dementia, says Hooshmand.