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by Jocelyn Mathern, R.D.
 
Soy has been a part of the human
diet for centuries, but only in the
last few years has soy truly
become mainstream. In the past,
consumers had to go to health
food stores to buy soy products. Now they
can find soy in grocery stores in a variety of
dietary supplements and foods—everything
from cereals, hot dogs and smoothies to
nutrition bars and even lattes. This trend is
not all that surprising, considering that 74
percent of Americans perceive soy as
healthy.
Research on soy is also growing. A traditional
area of soy research is women’s health.
New findings have recently been reported,
which will be highlighted in this article. In
addition, researchers are starting to look
deeper to find out what components of soy
are responsible for the health benefits and
whether there are different health effects
when you choose one soy product over
another.
Soy background
Major interest in soy began when
researchers, who studied populations where
soy is a major part of the diet, found that soy
may be protective against certain diseases.
Populations that consume soy foods on a
regular basis have lower incidences of certain
cancers. In addition, women in
Japan—where soy foods are eaten regularly—report fewer symptoms of
menopause and have lower rates of osteoporosis
than Western women. These findings
have fueled extensive research on the
health effects of soy.
Two main components in soy have
received the most attention: soy protein and
isoflavones. Soy protein is known for its
ability to lower cholesterol. In 1999 the U.S.
Food and Drug Administration (FDA)
approved a health claim for foods and
dietary supplements containing a certain
amount of soy protein. Soy isoflavones are
called phytoestrogens (plant estrogens)
because they have a chemical structure similar
to estrogen produced in our bodies.
When isoflavones are consumed, they can
act like weak estrogens. In addition,
isoflavones can also act as antioxidants.
Isoflavones have been the subject of extensive
research in the areas of bone health,
heart health, cancer and for reducing
menopausal symptoms.
All soy products are not created equal
As consumers, we can buy soy in several different
forms. Traditional soy foods like tofu
and soymilk are widely available. In addition,
a lot of non-soy foods such as cereal
and juice are being enriched with soy ingredients.
In the dietary supplement aisle soy
can be found in powdered beverages, nutrition
bars, capsules and tablets. When manufacturers
make these products, they have a
choice of different soy ingredients. Many
products are made with isolated soy protein
or isolated isoflavone extracts. The reason
for this is that whole soy ingredients, like
soy flour, can be difficult to use.
Manufacturers have to add a lot of soy flour
to get the amounts of protein and/or
isoflavones that they want. This can negatively
affect the taste and mouth feel of
products.
A concern some nutritionists have about
using isolated ingredients is that when you
concentrate one nutrient, you lose others.
When soy is eaten in countries like Japan, it
is usually the whole soy food and not isolated
soy protein or isoflavones. Most
studies looking at the health effects of soy
have focused on the protein and isoflavones.
However, soy contains many other nutrients
that contribute to a healthy diet, such as
fiber, essential fatty acids, vitamins and minerals.
Some researchers believe that it is the
combined action of all of the components in
soy that provide the full health benefits.
Soy germ ingredients are unique in this
aspect. Soy germ can be thought of somewhat
like wheat germ. It is a small portion of
the plant but is compact in nutrition. Soy
germ is of interest because it is the part of the soybean where the isoflavones are stored, so
it is naturally more concentrated in isoflavones
than ingredients like soy flour and soy protein.
Because soy germ is so concentrated, manufacturers
don’t have to process it as much as isolated
soy ingredients. Therefore, soy germ
ingredients still contain the other nutrients
like fatty acids and minerals that are naturally
found in soy.
Soy research update
Since researchers first linked a diet rich in soy
to reduced risk of disease, soy has been the
subject of hundreds of clinical studies. Every
few years a research symposium is held to discuss
new and emerging soy research. One of
the more exciting areas of research at the last
few symposiums has involved isoflavone
metabolism.
There are three different isoflavones in soybeans:
genistein, daidzein and glycitein.
Often the isoflavones found in soy foods or
supplements are attached to a molecule of glucose.
During digestion, bacteria in the intestines
must remove the glucose molecule
before the isoflavones can be absorbed
(isoflavones attached to glucose are referred to
as “glucosides” and isoflavones that have had
the glucose removed are called “aglycones”).
Once the molecule of glucose is removed,
isoflavones can either be absorbed “as is” or
they can be further broken down into other
compounds.
Of growing interest is the isoflavone
daidzein, which can be metabolized to a compound
known as equol. Not everyone who
consumes soy makes equol—only about onethird
of people produce equol. Researchers are
learning that people who make equol may
experience greater health benefits from
consuming soy than those who do not. The
cholesterol-lowering effects of soy may be
greater in people who produce equol. Women
who produce equol may experience more benefit
from soy isoflavones for the relief of hot
flashes during menopause. Therefore, equol
may help explain why some soy research is
positive and other studies find no effects.
Why do some people make equol and
others don’t? This is a puzzling question.
According to one study, women who were
equol producers tended to eat more carbohydrates,
plant protein and dietary fiber than
non-equol producers. It is not known if
changing your diet to include more of these
foods will help you become an equol producer.
However, eating soy foods as a part of a
healthy, well-balanced diet that is high in fiber
is a good idea.
Natural menopause relief
Recently it was announced that the Women’s
Health Initiative Study—a study of more than
16,000 women taking hormone replacement
therapy (HRT)—was stopped early because
researchers saw an increase in invasive breast
cancer, coronary heart disease, stroke and
blood clots. Researchers concluded that the
risks of combined hormone therapy outweigh
the benefits. As a result of this announcement,
many women have been looking for natural
alternatives for relief of menopausal symptoms
and protection from heart disease. Isoflavones,
being phytoestrogens, are potential alternatives
to HRT.
The research on soy for menopausal symptoms
can be confusing. Some studies show
great improvements, while others find little
improvement. One reason may be due to the
placebo effect that is often seen in studies.
Another reason could be equol producers
versus non-producers. It could also be that
women with a lot of symptoms may benefit
more than women with mild symptoms. A
recent research article published in the Journal
of Medicinal Food suggests that women with
the greatest number of hot flashes appear to
benefit the most from taking soy isoflavones.
The total effect of soy, including the placebo
effect, may be up to 50 percent overall
improvements in hot flashes. A dose of 50 mg
soy extracts in the form of tablets or capsules
may be beneficial with an upper limit of 100
mg per day.
Bone benefits
Estrogen helps protect women from bone
loss. During menopause women experience a
loss of estrogen, which increases the risk of
osteoporosis. HRT has been shown to protect
against bone loss, but due to potential risks of
HRT, researchers are interested in whether soy
isoflavones have similar benefits. Isoflavones
from soy germ have shown promising results
in bone health. A newly published study
found that a soy germ ingredient (SoyLife®)
was effective in the prevention of bone loss in
postmenopausal women. Researchers gave
203 postmenopausal women between the ages
of 48–62 isoflavone treatment for one year.
The women received either 40 or 80 mg
isoflavones (aglycones) daily or a placebo. In
addition, all women were given calcium and
vitamin D. Results showed that women
taking 80 mg of isoflavones had favorable
effects on bone mineral concentration at
the hip.
Soy germ is also currently part of a $4.5
million USDA study looking at the effects of
soy isoflavones on bone health. Four hundred
postmenopausal women are being studied for
two years to document the safety and efficacy
of soy isoflavones for osteoporosis. One third
of the participants are taking 80 mg
isoflavones daily, another third are taking 120
mg a day, and the last third is taking a
placebo. All of the women are being supplemented
with 600 mg of calcium and 400 IU of
vitamin D each day to ensure an adequate
intake of other bone-building nutrients.
Researchers hope to confirm that soy
isoflavones provide a natural alternative to
hormone replacement therapy for the prevention
of osteoporosis.
Soy germ research
In addition to promising studies on bone
health, soy germ has been the focus of several
other research studies in the areas of bioavailability,
estrogenic activity, menopausal
symptom relief, prebiotic effects, antioxidant
effects and safety. An interesting aspect of soy
germ is that it is higher in the isoflavone
daidzein than other soy ingredients. Since
equol is a metabolite of daidzein, the future
will tell whether these beneficial effects of soy
germ seen in research can be related to its high
daidzein content.
Conclusion
Research in the area of soy is still active and
growing. While emphasis has traditionally
been placed on women’s health, researchers are
starting to look at soy for additional health
conditions such as obesity and diabetes.
Therefore, we can expect to hear more about
soy research in coming years. We can also
expect to see new soy products on the market.
When you purchase soy food products, those
that provide the whole nutrient profile of soy
should be your first choice. If you choose a soy
supplement, it should be used in addition to a
well-balanced diet, under the guidance of your
physician or dietitian.
References upon request
For more information: www.talksoy.com and www.soylife.com
Jocelyn Mathern, R.D. is technical specialist for
Acatris Inc., a distributor of science-based
nutraceutical ingredients. Jocelyn is also currently
pursuing her master’s degree at the University of
Minnesota. For more information please contact
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