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Soy
Staves Off Alzheimer's in Monkeys
SAN
DIEGO (Reuters Health) - Soy may have a protective effect against
Alzheimer's disease, according to results of a new animal study.
Dr. Helen
Kim of the University of Alabama at Birmingham presented the results
of a 3-year study in which monkeys ate one of three diets including:
soy containing plant-based estrogen-like compounds called isoflavones;
soy without isoflavones; or a commonly used hormone replacement
drug containing estrogen. The 45 monkeys used in the study were
all female and had had their ovaries removed so that they acted
as a model for human menopause.
The study
findings were presented Tuesday at the national meeting of the
American Chemical Society held in San Diego, California.
Kim told attendees
that the monkeys that ate soy with isoflavones were much less
likely to have protein changes in their brains that are linked
with Alzheimer's disease.
``The bottom
line is that we found that soy with isoflavones suppress modifications
made on a protein that is essential for the development of Alzheimer's
disease,'' Kim told Reuters Health.
``By suppressing
the way that these protein modifications are made, I feel that
the soy with isoflavones is protective,'' she added.
However, Kim
expressed surprise that the team did not see the same protective
effect in the monkeys who received the hormone estrogen in their
diets.
``The effects
that we saw may be due to the fact that isoflavones are strong
antioxidants,'' she said. Antioxidants blunt the activity of free
radicals, which are molecules that are byproducts of the body's
normal processes that can damage body tissues.
Kim and her
colleagues were prompted to do their study by earlier research
that showed that estrogen might diminish a woman's risk of developing
Alzheimer's.
``We feel
pretty strongly, based on previous research, that estrogen is
neuroprotective. What my data suggest is that both soy and estrogen
are good for the brain but by different mechanisms,'' Kim told
Reuters Health.
Nevertheless,
Kim noted that her studies are done in monkeys and that future
research needs to be conducted in humans to know for sure if postmenopausal
women who eat soy will be protected from developing Alzheimer's
disease.
Alzheimer's
disease, a degenerative brain condition that leads to dementia
and eventual death, affects about 15% of older women. While hormone
replacement therapy--which many women take after menopause--is
known to protect against heart disease and osteoporosis, evidence
for its effect on Alzheimer's disease risk has been equivocal.
This is the
first study to look at the role of soy isoflavones (plant-based
estrogens normally found in soy) in primates to see if they affect
the onset of Alzheimer's disease.
Kim's research
was partially funded by the National Institutes of Health and
the United Soybean Board.
Reference
Source 89
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