Soy has been used
traditionally in China, Korea and Japan for thousands of years. As a
legume high in both protein and fat, it yields numerous products,
many of which are now part of large industries. Among the
traditional products are the unfermented tofu and soy milk, and the
fermented miso, soy sauce, tempeh, and natto. In the early days of
the “health food movement”, mid to late 1970’s,
these products were brought to the public’s attention by the
Japanese macrobiotic movement, and became adopted as excellent
additions to vegan and plant-based diets.
Since the late 1980s
there has been a great deal of emphasis on using soy for the health
issues of women. Curiously enough, that is also about the time that
soybeans began to be genetically engineered. I always found this
timing coincidence curious.
Soybeans are known to
contain both phytoestrogens and goitrogens.
Effect on women
Phytoestrogens
(genistein is one of them) are similar to the female hormone
estrogen, and thus they can have both positive and adverse effects.
They may diminish hot flashes in post-menopausal women; on the other
hand, when taken by pregnant women, genisteins may adversely affect
the reproductive system of their developing male and female embryos.
They may also provoke the same effects as excessive estrogen, and
encourage the growth of endometrial and breast tissue. Soy products
are recommended against osteoporosis because the assumption is that,
being estrogenic, they will have a positive effect on bone mineral
density, although that does not mean that they prevent fractures.
Soy weakens the thyroid
The presence of
goitrogens – substances that weaken the thyroid –
in soy has been known for at least 30 years. I mentioned that in my
book Food and Healing (Ballantine 1996), the first edition of
which was published in 1986. This is an issue that is mostly
overlooked in the great soy marketing push: soy does weaken the
thyroid. For clients who come to me for consultation, if they have
any thyroid issues, I will suggest that they completely avoid any
kind of soy, with generally good results. In addition, as a legume,
soy in its uncooked state contains substances called trypsin
inhibitors, also called proteinase inhibitors. These
substances interfere with the protein-digesting activity of the
digestive enzymes trypsin and chymotrypsin. Animals
fed raw soybean meal show reduced growth and extensive damage to the
pancreas. Cooking helps eliminate most of the trypsin inhibitors.
Growth problems
Soy is also a source of
phytic acid, or phytates. According to the Weston A. Price
Foundation
(http://www.westonaprice.org/brochures/SoyAlertTrifold.pdf),
high levels of phytic acid in soy reduce assimilation of calcium,
magnesium, copper, iron and zinc. High phytate diets have caused
growth problems in children. Phytic acid in soy is not neutralized
by ordinary preparation methods such as soaking, sprouting and long,
slow cooking, but need to be neutralized by fermenting.
Therefore, tofu and soy milk, which are unfermented,
are poor food choices, both for children and adults. Miso, soy
sauce, tempeh, and natto are better sources in this regard, but there
still is the problem of goitrogens, which appear to be linked to the
phytoestrogens in soy, the very substance that makes them desirable
for those looking at women’s issues. Let’s remember also
that allergies to soy are extremely common, especially among
children.
At this time (in the
first decade of the 21st Century), about 89% of the soy
crop in the United States is GMO, or genetically engineered, most
commonly to resist an herbicide. Studies on mice show that when fed
GMO soy, there are unfavorable changes in the liver, pancreas, and
testes of these laboratory animals. When these animals were switched
off the GMO soybeans and fed the standard non-GMO soy, their organs
returned to normal.
How to be safe with soy
To be safe, if you are
using soy products, it’s essential that they be organic,
non-GMO, and fermented, such as tempeh, natto, and soy sauce. I
think it’s OK to use tofu here and there, mixed into stir-fries
or other dishes, but not too much. I really don’t like soy
milk as a dairy substitute; it’s just a white liquid, like
milk is, but highly processed. Real homemade soy milk tastes like
bean water, which it is. The commercial stuff has a lot of
ingredients in it, including sweeteners – just read the label
carefully. While I have met women who feel that their hot flashes
have diminished from drinking soy milk, as a whole I would advise
against unfermented commercial soy as a healthy food, because of all
the other problems mentioned.
Annemarie Colbin, Ph.D.
ANNEMARIE COLBIN, Ph.D., CHES, is an award-winning leader in the
field of natural health She founded Natural Gourmet Institute for
Health and Culinary Arts (TM) in New York City in 1977, and is adjunct
professor of nutrition at the city’s Empire State College. She is the
author of four books, including The Book of Whole Meals (Autumn Press, 1979; Ballantine Books, 1983), The Natural Gourmet (Ballantine Books, 1989, 1991), and Food and Healing (Ballantine Books, 1986, 1996). Her website is: www.foodandhealing.com