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2010-09-09 12:11:34
By Jane Hughes Health correspondent, BBC News
CT scan Brain scan of a person with Alzheimer's
A new study suggests high doses of B vitamins may halve the rate of brain
shrinkage in older people experiencing some of the warning signs of Alzheimer's
disease.
Brain shrinkage is one of the symptoms of mild cognitive impairment, which
often leads to dementia.
Researchers say this could be the first step towards finding a way to delay the
onset of Alzheimer's.
Experts said the findings were important but more research was needed.
The study, published in the journal Public Library of Science One, looked at
168 elderly people experiencing levels of mental decline known as mild
cognitive impairment.
This condition, marked by mild memory lapses and language problems, is beyond
what can be explained by normal ageing and can be a precursor to Alzheimer's
and other forms of dementia.
Half of the volunteers were given a daily tablet containing levels of the B
vitamins folate, B6 and B12 well above the recommended daily amount. The other
half were given a placebo.
After two years, the rate at which their brains had shrunk was measured.
The average brain shrinks at a rate of 0.5% a year after the age of 60. The
brains of those with mild cognitive impairment shrink twice as fast.
Alzheimer's patients have brain shrinkage of 2.5% a year.
The team, from the Oxford Project to investigate Memory and Ageing (Optima),
found that on average, in those taking vitamin supplements, brain shrinkage
slowed by 30%.
In some cases it slowed by more than 50%, making their brain atrophy no worse
than that of people without cognitive impairment.
'Protecting' the brain
Certain B vitamins - folic acid, vitamin B6 and B12 - control levels of a
substance known as homocysteine in the blood. High levels of homocysteine are
associated with faster brain shrinkage and Alzheimer's disease.
Continue reading the main story
Start Quote
These vitamins are doing something to the brain structure - they're protecting
it, and that's very important because we need to protect the brain to prevent
Alzheimer's
End Quote Professor David Smith Oxford University
The study authors believe it was the B vitamins' effect on levels of
homocysteine that helped slow the rate of brain shrinkage.
The study author, Professor David Smith, said the results were more significant
than he had expected.
"It's a bigger effect than anyone could have predicted," he said, "and it's
telling us something biological.
"These vitamins are doing something to the brain structure - they're protecting
it, and that's very important because we need to protect the brain to prevent
Alzheimer's."
He said more research was now needed to see whether high doses of B vitamins
actually prevented the development of Alzheimer's in people with mild cognitive
impairment.
The Alzheimer's Research Trust, which co-funded the study, also called for
further investigation.
"These are very important results, with B vitamins now showing a prospect of
protecting some people from Alzheimer's in old age," said chief executive
Rebecca Wood.
"The strong findings must inspire an expanded trial to follow people expected
to develop Alzheimer's."
B vitamins are found naturally in many foods, including meat, fish, eggs and
green vegetables.
Experts are advising against taking higher than recommended levels in the light
of these findings.
Chris Kennard, chair of the Medical Research Council's Neurosciences and Mental
Health Board, said: "We must be cautious when recommending supplements like
vitamin B as there are separate health risks if taken in too high doses.
"Further research is required before we can recommend the supplement as a
treatment for neurodegenerative diseases, such as Alzheimer's."