Soy May
Help Protect Brain From Alzheimer's - Study
By Deena
Beasley
LOS
ANGELES (Reuters) - Eating more soy could help stave off the irreversible brain
disorder Alzheimer's disease, which afflicts more than half of Americans over
the age of 85, researchers said on Tuesday.
Soy,
rich in phytoestrogen compounds and already said to reduce risk for heart
disease and osteoporosis, may help protect against the onset of Alzheimer's
disease, especially in post-menopausal women, according to a study presented at
a meeting of the American Chemical Society in San Diego.
A
three-year animal study found that plant-based estrogens found in soy, called
phytoestrogens or isoflavones, appear to reduce the number of protein changes in
the brain that are associated with Alzheimer's disease.
"There
is some evidence that women who don't take estrogen replacement therapy are at
greater risk for Alzheimer's so we wanted to compare the benefits of soy with
common estrogen therapy," Helen Kim, a professor at the University of
Alabama at Birmingham, and lead researcher for the study, said in a telephone
interview.
Alzheimer's,
characterized by a build-up of plaque and tangles inside the nerve cells in the
brain, affects about 4 million people in the United States. By the middle of
this century, as many as 14 million Baby Boomers could have Alzheimer's,
according to the Alzheimer's Association.
The
study was done with aged female monkeys that had their ovaries removed,
considered to be animal models for human menopause, Kim said.
During
the three-year study, funded by the National Institutes of Health, 45 monkeys
were fed one of three diets -- soy with isoflavones, soy without isoflavones and
soy without isoflavones and Premarin, a common estrogen therapy made by American
Home Products Corp. .
Fifteen
monkeys were in each diet group. The scientists then examined the brain tissue
of monkeys in each group for some of the protein changes that are markers of
Alzheimer's.
Kim said
her team found fewer Alzheimer's-linked protein changes in the brains of monkeys
that received soy with isoflavones, compared with both other groups.
Improper
function of certain proteins in the brains of people with Alzheimer's can cause
the skeletal structure of nerve cells to collapse.
Kim said
the same lack of change was not evident, at least to the same extent, in the
brains of the animals that were given Premarin. Kim suspects that isoflavones
and real estrogens, such as those in Premarin, may both be beneficial for the
brain but work through different mechanisms.
"We
now need to follow up with more animals to look at how the protein changes
affect brain function," the researcher said.
Women,
who undergo a rapid estrogen loss after menopause and historically live longer
than men, are most at risk for Alzheimer's, but men also succumb to the disease.
Men can
also benefit from eating more soy, Kim said.
"Estrogen
is viewed as a female hormone, but it really isn't. Without estrogen male mice
don't develop normally as far as sexual behavior and aggression," the
researcher said.
She
warned that people should consume their soy in food, rather than supplements,
where the risk of toxicity is uncertain.
"Make
chili with textured soy or a smoothie with soy milk. You can even make a really
good cheesecake with soy. The thing is that it can easily be incorporated into
good, familiar foods," Kim said.