So long, chicken. Hello tofu.
Tofu and a host of other products made from the mighty soybean
are pushing aside meat, milk and even ice cream on grocery store
shelves these days as scientists rave about the health benefits of
soy.
Most recently, the U.S. Food and Drug Administration cleared the
way for food companies to include labels that say eating 25 grams a
day of soy protein, when included in a diet low in saturated fat
and cholesterol, ``may reduce the risk of heart disease.'' Soy
protein boosts good cholesterol and sweeps bad cholesterol out of
the body before it can clog arteries.
But that's old news in the scientific community.
What drew 600 scientists to a conference on soy in Washington,
D.C., on Oct. 31 were the intriguing new findings on the
cancer-fighting properties of isoflavones, a plant-based form of
the hormone estrogen that is unique to the soybean.
Isoflavones appear to help strengthen bones, reduce the
unpleasant symptoms of menopause and, most importantly, control how
quickly cells replicate, which could be beneficial in preventing
the out-of-control cell growth associated with cancer. The National
Cancer Institute recently listed genistein, the main isoflavone in
soy, as one of four ``superior'' anti-cancer agents.
Isoflavones also are showing real potential as a supplement for
hormone replacement therapy in post-menopausal women and as a
bone-fortifying agent to help guard against osteoporosis.
When Mark Messina, a respected authority on soy products and
adjunct professor of nutrition at Loma Linda University, started
studying soy at the National Cancer Institute in the late 1980s,
there were roughly a dozen scientific papers on the topic and tofu,
the only soy product readily available, was a specialty item tucked
away in health food stores.
``Now everybody's talking about soy and cancer, soy and
menopause and all these things,'' Messina said. ``You see
television commercials advertising soy supplements for hot flash
relief and prostate health. Kellogg's announced recently that it's
coming out with a soy cereal. It's clearly very interesting and
intriguing, and that's why a lot of people are talking about it.
And industry is responding with an amazing array of products.''
But that doesn't mean everyone should run out and stuff
themselves with tofu.
``The evidence is really intriguing,'' said Messina, whose 1994
National Cancer Institute report on soy as a potential cancer
fighter is considered a cornerstone of the current explosion in
research. ``But one thing is clear: We have a long way to go before
we can speak in a conclusive manner about any of this stuff.''
Take breast and prostate cancers. There is intriguing evidence
that men who drank isoflavones in soy milk had less risk of
developing prostate cancer, but the results are more mixed when it
comes to breast cancer.
One study found a combination of the soy-based soup additive
miso and the anti-cancer drug tamoxifen reduced breast cancer
tumors in lab rats, while there were no changes in rats who only
got the drug. But, according to Dr. Claude Hughes, director for the
Center for Women's Health at Cedars-Sinai Medical Center in Los
Angeles, another study hints that isoflavones might actually
stimulate cancer cell growth in post-menopausal women with low
estrogen levels.
Hughes is also lead investigator on another study that found a
diet high in soy actually can trigger subtle changes in the
development of a fetus. Are those changes good or bad? There's
potential both ways, and right now no one can say for certain which
one will prevail, Hughes said.
The problems are complex because people's bodies change with
age, so a diet high in soy might be beneficial at one age and
detrimental at another.
``What do you do?'' Hughes said. ``Well, if you're a man or
woman in your 40s and you're not planning to make babies, having a
few servings of soy foods per week is a good idea. If you are a
28-year-old woman who is actively trying to get pregnant, the
advice is very simple: Eat a broad-based diversified diet. Be a
grazer. Don't eat huge quantities of anything. Don't be a
cheeseburger junkie. Don't be a tofu junkie. Just move around. Eat
a little bit of everything.''
The effects of soy are so mild it won't make much of a
difference for anyone when consumed in moderation. Messina said it
takes roughly 60 milligrams of isoflavones a day -- about two
glasses of soy milk -- to get the potential anti-cancer benefits of
soy. It takes four soy entrees to get enough soy protein to help
ward off heart disease.
More definitive answers are coming. The prostate cancer and
child development studies were published in the last three weeks,
about the same time the FDA finally approved the new soy labeling
rules. Messina said where there were only a dozen published studies
on the topic in 1985, there are now more than 2,000.
Hundreds of scientists around the globe are turning their
microscopes to soy in search of ways to prove or disprove its
cancer-fighting ability or its benefit as a natural alternative to
hormone replacement therapy.
Good science requires patience. Messina notes that the first
scientific paper of the heart health benefits of soy protein was
published in 1967, but it took more than two decades for scientists
-- and ultimately the marketplace -- to catch on. And that was easy.
Checking cholesterol is as simple as pricking a finger and drawing
a blood sample. Cancer is more enigmatic, elusive and influenced by
a host of variables scientists are only beginning to understand.
``We know soy protein lowers cholesterol, but pretty much most
of the other effects are speculative,'' Messina said. ``There is a
lot of research, but it takes a lot before you can really know
something with any certainty. I can tell you there wouldn't be the
enthusiasm and excitement about soy foods if they were only a good
source of protein that's low in saturated fat. Obviously, people
are hoping it is a lot more than that. And only time will tell.''
Messina and Hughes agree that consumers should embrace soy
products as part of a balanced diet, but not overdo it -- an
American tradition. Soy protein and isoflavones are a good addition
to a healthy lifestyle but will never be that proverbial magic
bullet against disease.
``Instead of looking for magic, maybe we should look for
wisdom,'' Hughes said. ``And the wisdom is to take advantage of
sets of interventions which, hopefully in some additive way, will
be robust in sum total.''
Cedars-Sinai Medical Center in Los Angeles is seeking women
experiencing ``hot flushes'' -- also known as hot flashes -- for a
study of soy-based phytoestrogen's role in moderating the
unpleasant symptoms that mark the onset of menopause.
The hospital's Center for Women's Health is one of 17 sites
conducting a national study of phytoestrogens, which show promise
as a treatment without the side effects of progestin, a hormone
replacement therapy drug.
