Bloom is Off the Soy
September 19, 2006
It's astonishing how quickly a wide range of soy-based foods and
drinks has flooded our groceries and delis. Most consumers are sure
they are doing the right thing by replacing dairy with soy products
because they are so "health-promoting" -- especially new mothers who
are feeding their infants soy-based formulas. However, there is a small
group of nutrition experts who strongly disagree about the so-called
health properties of soy. In fact, they fear soy might pose a danger to
health, in particular reproductive well-being. I wrote about these
concerns a number of months ago, but at that time large studies
investigating soy were not yet available. That has changed and the
results have taken many people by surprise.
By far the largest study was one done on mice at the National
Institutes of Health's Institute of Environmental Health Sciences. It
looked at genistein, one of the isoflavones (plant estrogen substances
also called phytoestrogens) contained in soy. For this study,
researchers injected genistein into groups of newborn female mice at
three different levels of dosages, all within the equivalency of what a
human baby might drink in soy-based formula. The mice in all three
groups showed disruption in the development of their ovaries. As they
matured, they had irregular menstrual cycles, problems with ovulation
and eventually with fertility. The mice that received the highest
dosage of genistein were infertile. Those who received lower doses were
sub-fertile, meaning they had fewer pregnancies and fewer pups per
litter. An NIH spokesperson acknowledged that there was no way to know
for certain how these findings translate to humans, but they warrant
caution. Another spokesperson expressed the belief that the
phytoestrogen would likely affect these children as adults, if not in
childhood.
The second startling study came from the American Heart Association,
which formed an expert committee to review a decade of randomized
studies on soy's benefits. This was especially important because in
1999 the Food and Drug Administration (FDA) gave manufacturers of
soy-based foods permission to add labels that proclaimed these foods to
be heart-healthy based on studies that showed consuming at least 25
grams of soy each day lowered cholesterol. Shortly after that time, the
AHA recommended making soy part of a heart-friendly diet.
Now, some six years later, the AHA committee reviewed 22 studies on
dietary soy protein. The committee's findings: Consumption of large
amounts of soy protein has virtually no effect on LDL levels, reducing
them a mere 3%. Soy consumption does not raise good cholesterol (HDL)
at all, nor does it show any beneficial effect on blood pressure. The
committee also reviewed 19 studies on soy isoflavones alone, which were
supposedly associated with relief of menopause symptoms. The review
found that isoflavones do not reduce menopause discomfort nor does soy
protein.
Furthermore, the committee found that isoflavones do not help
prevent breast, uterine or prostate cancer. (The Solae Company, which
represents the industry, had already quietly withdrawn its application
to the FDA to label soy protein as having anti-cancer benefits.) Or
course these findings beg the question of what it was that motivated
the American Heart Association and the FDA to so aggressively promote
soy's benefits... but that's a subject for a different article.
UNRAVELING THE CONFLICTING REPORTS
Clearly these findings are a striking blow against the common
beliefs about soy. To learn more about them and what was behind the
previously glowing reports of soy's benefits, I called Kaayla Daniel,
PhD, author of The Whole Soy Story: The Dark Side of America's Favorite
Health Food (New Trends). Dr. Daniel explains that much of the previous
research on soy (primarily funded by the soy industry) was based on
meta-analysis studies. For meta-analyses, researchers gather a number
of studies together on a given subject and average out the congregate
findings. Meta-analyses are valuable for providing hints about what
might be actually going on and suggestions for appropriate follow-up
randomized studies, but they are not considered reliable last-word
research.
The first weakness in meta-analyses is that researchers can cherry
pick among studies and by doing so influence findings, says Dr. Daniel.
And since findings are averaged out, a negative study or two will be
overwhelmed by favorable ones. Many years ago, she says, there were
some solid studies on soy, but they were "put out to the field" in
order to find ways to modify the soy protein, what is left after oil is
extracted from the beans to turn it into acceptable animal feed. These
studies investigated what amino acids, fatty acids, vitamins and
minerals should be added to soy protein to make it safe and to protect
reproductive function. Dr. Daniel adds that the information gained from
these studies has not made its way to many of the soy-based products
that humans now eat.
The Soy That's in Our Food
To find out more about the soy that is in our food supply I called
Carolyn Dean, MD, ND, who has done extensive research on a number of
digestive-related topics and is author of IBS for Dummies (Wiley). Dr.
Dean points out that the wide varieties of soy-based foods require
extensive processing to get them to the state in which they can be used
as the foods now on our shelves -- they are far from "natural." The
beans are cooked, crushed and heated to high temperatures and then put
through a solvent extraction process to remove the oil. The now
defatted meal is mixed with sugars and an alkaline solution to remove
the fiber and the resulting curds are spray dried at high temperatures,
which does two things -- produces high-protein powder... and peroxides
the oils making them pro-inflammatory. The end result is food that is
bereft of vitamins and likely minerals, she says, and far removed from
being a natural wholesome food. And there are other problems.
Because soy has a high level of phytic acid, it blocks digestion of
grains, which are an important source of minerals. Additionally, soy
contains trypsin inhibitors and these interfere with protein digestion.
Adding to these problems, the body does not absorb the B-12 in soy,
which in turn creates a nutritional void for vegetarians who consume
soy protein as a way of providing themselves with this important B
vitamin.
Even so, some soy products are reasonably healthy. Dr. Dean, who
also studied Chinese medicine, says that the Chinese did not eat soy
until they discovered that fermenting would turn it into a useful food.
In fact, fermented soy is largely the type of soy that Asians consume
today. Fermenting involves treating soy with a mold for a day or so.
Fermented foods include tempeh (not to be confused with tofu, which is
not fermented), which has a nutty mushroom taste... miso... natto...
and tamari sauce. However, because soy exists in so many foods today as
vegetable oil, binders and the like, even people who are wary of soy
probably consume some of it almost daily. Consequently, Dr. Dean
advises limiting fermented soy product consumption to not more than
every third day.
The soy industry has ballooned in recent years and now represents
more than a billion dollars in sales per year. You can expect to hear
much more from both the industry and independent researchers in the
future concerning soy and health issues. I'll be sure to keep you up to
date. In the meanwhile, while searching your food store for
high-protein foods, take a pass on the ones "enriched with soy
protein."
Be well,
Carole Jackson
Bottom Line's Daily Health News
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Cure Memory Loss with Backyard Herb
Think you have memory challenges? Imagine memorizing all those
complex picture-characters in Japanese writing.
Maybe that's why hundreds of Japanese patients were so grateful
recently when a doctor reversed their short-term memory loss with a
simple tea made from eyebright -- an herb that you can grow in your own
garden.
While eyebright as a memory booster is new, its power to help vision
has been famous since the 14th century. It strengthens the optic nerve,
making the eye less vulnerable to cataracts. This nerve-boosting also
may help the brain, which, after all, is made up of nerve cells.
Read on...
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Sources:
Bloom Is Off the Soy
Kaayla T. Daniel, PhD, author of The Whole Soy Story: The Dark
Side of America's Favorite Health Food (New Trends), and a
board-certified clinical nutritionist based in Santa Fe, New Mexico.
Carolyn Dean, MD, ND, author of IBS for Dummies (Wiley) and
The Miracle of Magnesium (Ballantine). She is in private
practice in New York City.
---
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