High
homocysteine tied to stroke, Alzheimer's...
B
Vitamins, folate can reduce this acid
Moderate elevations of homocysteine are associated with
a more than five-fold increase in the risk for stroke and almost
triple the risk for Alzheimer’s disease, according to research
reported in the October issue of Stroke: Journal of the American
Heart Association.
Homocysteine
is an amino acid believed to be toxic to blood vessels.
Several studies have linked high blood levels of it to increased
heart attack risk. This study found that homocysteine
levels in patients with stroke, Alzheimer’s disease or
vascular dementia were consistently higher than homocysteine
levels in age-matched healthy volunteers.
“Since
B vitamins and foods fortified with folate can reduce
homocysteine levels, this study suggests that B vitamin
supplementation may be appropriate for most adults. It warrants
a large placebo-controlled study of folate, and vitamins B6
and B12 in people at risk from dementia and
stroke,” says lead author Stephen P. McIlroy, Ph.D., a
lecturer in geriatric medicine at Queen’s University in
Belfast, Ireland.
McIlroy
and his colleagues studied 83 Alzheimer’s patients (average
age 77); 78 patients with dementia caused by poor blood flow to
the brain, a condition called vascular dementia (average age
77); 64 stroke patients (average age 74) and 71 healthy
volunteers (average age 74).
There
is some disagreement among scientists about what constitutes an
elevated homocysteine level. Here, researchers designated
the upper quartile of homocysteine levels of the healthy
volunteers – 13.3 micromoles per liter (μmol/L) or higher
– as an elevated level.
They
also collected data on education, diet, blood pressure,
cholesterol, and smoking history. Several of these factors
are associated with the risk for Alzheimer’s disease, and
smoking directly affects homocysteine levels, he says.
The
researchers also used DNA testing to determine if any of the
subjects had a variation in the gene methylenetetrahydrofolate (MTHFR),
which can adversely affect folate metabolism.
After
correcting for other risk factors, elevated homocysteine was
associated with a 2.9 times greater risk for Alzheimer’s
disease than risk in volunteers with lower levels of
homocysteine. The stroke risk was 5.5 times greater, and
for vascular dementia, it was 4.9 times greater. These
findings were not related to having the MTHFR mutated gene.
In
an accompanying editorial, Amos D. Korczyn, M.D., of the
department of neurology at Tel-Aviv University Medical School in
Ramat-Aviv, Israel, notes that there is no ultimate proof that
homocysteine causes stroke or dementia. He says that
elevated homocysteine could theoretically be the result of
stroke or dementia. Additionally, he notes that poor diet
– which is common in old age, particularly among people with
dementia – may raise homocysteine.
However,
Korcyzn also says it may now be appropriate to recommend that
elderly people and particularly those with higher risk of
vascular disease or dementia take vitamins B12 and
folate.
“Since
dietary habits are so different among people, it may be
appropriate to recommend 2 to 5 mg folic acid and a similar dose
of vitamin B12 daily,” he says. “This
recommendation is based on the known safety of both vitamins,
which do not have side effects even if used in excessive
amounts, and their low cost.”
McIlroy
notes that in the United States many foods, especially cereals,
are fortified with folate but this is not the case in the United
Kingdom. Even with the fortified foods, a daily vitamin B
supplement may be warranted especially after a stroke, he says.
The
American Heart Association recommends that healthy people obtain
adequate nutrient intakes from foods eaten in variety and
moderation, rather than from supplements.
McIlroy’s
co-authors are Kevin B. Dynan, M.D.; John T. Lawson, M.D.;
Christopher C. Patterson, Ph.D.; and A. Peter Passmore, M.D.