Soy : can it feminize men and boys?

From:
http://www.drweil.com/app/cda/drw_cd...stionId=312211

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Today's Question
Given that soy products could stimulate estrogen-sensitive cells in
the body, are men at any risk of developing effects of estrogen excess
(like feminization) if these foods constitute a significant part of
their diet?

-- Jon Awerbuck

Today's Answer
(Published 11/10/2003)

When you consider that millions of men in China, Japan and other Asian
countries have had soy foods in their daily diets from earliest
childhood, you can appreciate that the plant estrogens they contain
have no discernible effect on male sexual development, and no
feminizing effects at all. Given the huge populations of Asian
countries there's no reason to think that soy affects male fertility,
either.

However, concerns in the Western world about the effects on boys and
men from eating soy foods have been raised repeatedly and addressed in
numerous laboratory and population studies. Researchers at the
University of Pennsylvania surveyed men and women who, as babies, were
given soy- based formulas to see if any of them had sexual, fertility
or hormonal problems; they were then compared to a matched group
raised on cow's milk formula. The only discrepancies noted were some
minor menstrual complaints among the women (their periods lasted
one-third of a day longer and they reported slightly more menstrual
pain). Results were published in the August 15, 2001, issue of the
Journal of the American Medical Association.

In March 2002 the Journal of Nutrition published results of a survey
of men consuming soy foods or supplements containing 40-70 milligrams
of isoflavones (the phytogenic components). None of the studies showed
that consuming soy had any effects on reproductive hormones or semen
quality, both changes that you might expect to see before any overt
"feminization" would occur.

Including soy foods in your diet may enhance your health and help
protect against heart disease and prostate cancer. I recommend two
servings per day of such soy foods as tofu, tempeh (soy protein), soy
milk or edamame. That would add up to about 40 milligrams of
isoflavones, less than the amount consumed in the traditional Asian
diet. The earlier in life one begins to consume soy, the greater the
protection against breast and prostate cancer seems to be.

Andrew Weil, MD