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By Eric Rosenberg
After the U.S. Food and Drug Administration
allowed food manufacturers two years ago to claim that soy-based
foods help lower the risk of heart disease, a bumper crop
has appeared on grocers' shelves.
Consumers can find soy hot-dogs, soy garden
burgers, soy cheese, milk and butter, breads made from soy
flour, soy power bars, soy ``meats'' and raviolis - not to
mention the old standbys of tofu, miso and soy sauce.
The growth
in soybean usage in the last decade has outpaced every other
food commodity, including rice, corn, cotton and wheat.
US farmers are expected to plant a record
76.7 million acres
of soybeans this year, up 3 percent from last year's record
planting, according to the US Department of Agriculture.
But conflicting
opinions are now emerging among researchers about soy's health
benefits.
Where soy was once universally regarded
as a wonder food - capable of stemming disease, warding off
cancer and providing inexpensive nutrition to boot - now there
is some concern that soy
may be a source of estrogen and, as such, could
promote breast cancer in some women.
Soy has this healthy cache. Everybody
thinks that soy can't be anything other than good,'' she said.
Initially, the soy enthusiasts made it sound like the scientific
evidence was very sound.
But we need
more to determine whether it is safe.
Like all foods, soybeans are comprised
of complex chemical components. The main components are protein,
essential fatty acids and to a lesser degree what are known
as isoflavones.
This family of chemicals is also found
in other legumes. The versions in soybeans - genistein, daidzein,
glycitein and equol - are also phytoestrogens - plant-derived
weak estrogens, chemically similar to the female hormone estrogen.
As a result, some
physicians caution breast cancer patients against eating too
much soy for fear it could promote tumor growth
in women whose disease is sensitive to estrogen.
In addition, health agencies of New Zealand,
Australia and Great Britain have voiced concern
about the safety of soy-based infant formula for
fear that it might spark reproductive or thyroid problems
in babies in later life.
Wahida Karmally, spokeswoman for the American
Dietetic Association, which represents US nutritionists, says
the advice to women who have breast cancer is to use soy in
moderation. "We don't know if it's dangerous, but we
should be conservative about it until we do know,'' she added.
Much of the current debate over soy safety
began two years ago when two FDA scientists raised red flags
at a time when the agency was considering whether to allow
the health claim by food manufacturers.
Daniel Sheehan
and Daniel Doerge, both senior toxicologists at the FDA, strongly
opposed the soy health claim and wrote a memorandum outlining
their concerns.
``We oppose this health claim because
there is abundant evidence that some of the isoflavones found
in soy demonstrate toxicity
in estrogen sensitive tissues and in the thyroid,''
they said.
``Given that a women's own estrogens are
a very significant risk factor for breast cancer, it is unreasonable
to approve the health claim until complete safety studies
of soy protein are conducted,'' they wrote, citing 28 studies
suggesting the possible toxic effects of soy.
Because the FDA regulates drugs that contain
estrogen, soy products should have warning labels advising
consumers about the chemical contents, according to Sheehan
and Doerge. ``The public
will be put at potential risk from soy isoflavones in soy
protein isolate without adequate warning and information,''
they wrote.
Although the FDA leadership ultimately
overruled the two scientists, officials acknowledge the concerns
should be taken seriously.
Regina Ziegler, an epidemiologist with
the US National Cancer Institute and a soy researcher, said
that more studies are under way into soy safety, including
one by the National Institutes of Health on infant formula.
But, she cautioned, ``there's not the
perfect study out there It's not like there's just one study
that needs to be done and then we'd get the answer.''
Hearst
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