Speaking at the British Science Festival in Bradford on Tuesday, Celeste de Jager, a neuropsychologist at Oxford University, said that taking vitamins B6, B12 and folic acid in medicinal quantities reduced the overall shrinkage of a person's brain by 30% over the course of the two-year study.
Her work, published in the International Journal of Geriatric Psychiatry, was carried out on 270 men and women over 70 who had mild cognitive impairment (MCI), a condition that affects one in six elderly people and which can interfere with memory, language and other mental functions. About half of the people with MCI go on to develop Alzheimer's within five years of the initial diagnosis.
Taking B vitamins and folic acid is known to control the levels of an amino acid called homocysteine in the blood. High levels of this chemical can damage blood vessels and are associated with increased risk of dementia.
"High homocysteine is a known risk factor for cognitive decline in the elderly and Alzheimer's disease and also for other kinds of dementia like vascular dementia," said de Jager. "It can be damaging to the endothelial lining of the blood cells. It also binds to receptors in the brain that are on the neurons and it seems to contribute the atrophy that's associated with Alzheimer's."
The elderly are more susceptible to this effect of high homocysteine, she added, because levels rise with older age, possibly due to poorer absorption of B vitamins in diet as people age.
To keep homocysteine levels down, she said, people should eat more meat, fish and green vegetables, and reduce consumption of alcohol, which is known to deplete the body of vitamin B12.
Across the whole group, de Jager found that the people taking vitamins had a 30% reduced decline in brain tissue over two years compared with placebo. In people with the highest homocysteine levels in the blood at the start of the experiment, however, the vitamins provided most benefit, reducing brain shrinkage by 50% in these cases.
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