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Dana Rosen-Perez
Read a few soy-product advertisements,
and it quickly becomes clear that proponents of this humble
bean have never met a health problem that, according to them,
soy can't help.
But are these
claims legitimate? Can soy do all its promoters claim?
Some scientific studies that set out to
confirm the health benefits of soy have yielded encouraging
results, but others have provided reason to be skeptical,
even concerned, about incorporating soy into your diet. So
should you or shouldn't you run out to buy those soy burgers?
Isoflavones are phytoestrogens
-- they act like the hormone estrogen.
Many in the scientific and medical communities have proposed
that soy plays a part in cancer prevention. The idea that
soy might offer such protection stems from the lower rates
of these illnesses in Asian countries, where soy consumption
is common.
Soybeans contain plant compounds called
isoflavones.
Many different studies point to the role of isoflavones in
breast cancer prevention. Nevertheless,
isoflavones are phytoestrogens -- they act like the hormone
estrogen.
This raises
the question of whether soy consumption is bad for women with
estrogen-receptor-positive breast cancer.
Estrogen-receptor-positive breast cancers
have molecules (receptors) on them that permit the female
hormone estrogen to stimulate their growth.
Women Get
Mixed Messages
Indeed, the estrogenic effects of soy
consumption on breast tissue was shown in a 1996 study involving
premenopausal women who consumed soy over a 4-month period,
as well as in the 1999 analysis of a study involving women
who consumed soy for 2 weeks.
Many women with estrogen-receptor-positive
breast cancer take the drug tamoxifen as an antiestrogen.
Although the effects of soy when taken with tamoxifen are
unknown, Margo Woods, MD, associate professor in the Department
of Family Medicine and Community Health at Tufts University
Medical School, says she
doesn't think it would be wise to "take a dietary food
that might interfere with the effects of tamoxifen."
Although prostate cancer is not studied
as much as breast cancer, there is support from different
kinds of studies that indicates isoflavones might prevent
this disease.
Soy and Heart
Health
As of October 1999, the FDA permits labels
on products containing soy protein, such as soymilk, tempeh,
and soy cheese, to include statements about the role of soy
in reducing heart disease.
According to an FDA spokesperson, soy-food
makers are only authorized to make health claims related to
heart disease because the soy bean association that petitioned
the FDA specified cardiovascular health as the topic for review.
Concluding that foods containing soy protein, included in
a diet low in saturated fat and cholesterol, may reduce the
risk of heart disease by lowering cholesterol levels, the
FDA recommends that we incorporate four servings of 6.25 grams
of soy protein into our daily diet.
Foods Versus
Supplements
A handful of soy supplements offer soy
protein, but many contain only soy isoflavones. Since soy
proteins seem to offer health benefits above and beyond those
of the isoflavone components, Dr. Woods suggests that people
consume soy foods as opposed to supplements.
If you do consider supplements, bear in
mind that the average Japanese person consumes 30 milligrams
of soy isoflavones per day. You may wish to select one of
the many soy supplements containing 25 milligrams of isoflavones
rather than those containing megadoses.
About
52% of the United States soybean crop is genetically modified.
Many environmentalists have protested
genetically modified foods, but this issue does not seem to
worry proponents of the health benefits of soy.
CBS
Health Watch Aug.
2000
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