| Q: Is Soy Dangerous?
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| | Conclusion: We still do not know all the
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| Q: I've been reading quite a bit about
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| | answers where soy and breast cancer are
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| the dangers of consuming too much soy,
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| | concerned. However, the evidence is
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| but to date I have not figured out what
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| | sufficient to say that soy consumption
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| those dangers are other than too much
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| | does not increase risk of breast cancer
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| estrogen production with its consequences
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| | and may reduce risk in some people,
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| for higher cancer risk. A friend told me
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| | especially if soy is consumed from an
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| that a woman with a Vegetarian Nutrition
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| | early age. For those who have
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| course to her credit told her that she
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| | estrogen-positive breast cancer, it also
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| would recommend rice beverage over soy.
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| | appears safe to use soy in moderation.
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| Why? Would you kindly clarify this matter
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| | Soy and Thyroid
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| for me.
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| | Claim : Soy contains natural chemicals
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| Thanks,
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| | known as goitrogens that interfere with
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| Joyce Ward, Winnipeg
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| | thyroid function. These can cause an
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| A: Dear Joyce,
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| | enlargement of the thyroid gland (a
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| Thank you for the opportunity to provide
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| | “goiter”) and symptoms of
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| some clarity about this issue. As you may
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| | hypothyroidism, such as lethargy,
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| be aware, soy has enjoyed considerable
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| | dullness, coldness, and depression.
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| favourable press over the past decade. We
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| | It is true that soy contains goitrogens,
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| have seen reports of soy reducing risk of
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| | as do many other foods such as
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| heart disease, cancer, osteoporosis, and
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| | cruciferous vegetables (cabbage,
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| reducing symptoms of menopause. Just when
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| | cauliflower, broccoli, and brussel
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| soy seemed to be on top of the world,
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| | sprouts), sweet potatoes, lima beans, and
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| articles and websites began to appear
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| | millet. However, these foods have been
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| claiming that this new-found health hero
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| | found only to cause problems when iodine
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| was really a villain in disguise. Soy
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| | intake is low , because goitrogens do
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| bashers said all the hype about soy was
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| | their damage by interfering with the
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| really just propaganda, and that in
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| | thyroid gland's ability to utilize
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| truth, soy was not a health food, but
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| | iodine. Between 1951 and 1961, several
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| rather a dangerous substance that should
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| | cases of goiter were diagnosed in infants
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| be carefully avoided by humans. In fact,
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| | who had been fed infant formula made from
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| anti-soy advocates claim that eating soy
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| | soy flour. These cases are frequently
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| raises risk of cancer, osteoporosis,
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| | cited by the anti-soy lobbyists to prove
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| thyroid problems, birth defects,
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| | soy damages thyroid function (especially
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| reproductive problems, nutritional
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| | in infants). But not a single case of
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| deficiencies and Alzheimer's disease.
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| | goiter in infants has been caused by soy
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| This has left consumer wondering if soy
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| | formula since the 1960s. At that time the
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| is really a saint or a sinner.
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| | soy formula base was changed from soy
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| First, it is important to understand that
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| | flour to soy protein isolates, which are
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| soy is not something new. The soybean has
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| | low in goitrogens, and manufacturers
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| been used for food for centuries,
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| | began fortifying soy formula with iodine.
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| particularly in the Orient. Traditional
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| | Soy does not cause thyroid problems in
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| forms of soy foods included fresh or
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| | healthy, well-nourished people who are
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| frozen beans from the soy pod (called
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| | not deficient in iodine. However, people
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| edamame ), soy milk, tofu, and fermented
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| | who do not have a reliable source of
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| foods, such as tempeh, miso and soy
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| | iodine could increase their risk of
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| sauce. More recently soy has become a
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| | thyroid problems if they eat a lot of soy
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| huge hit in North America, with all of
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| | and/or other foods rich in goitrogens.
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| the traditional forms of soy widely
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| | Iodized salt, dairy products, and fish
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| available in addition to numerous others,
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| | are the main dietary sources of iodine,
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| such as soy nuts, soy-based meat
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| | and most multivitamin/mineral supplements
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| analogues, soy-based protein beverages,
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| | provide the recommended daily allowance.
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| soy chips, soy ice cream, soy yogurt, and
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| | So the answer is not to avoid soy or
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| the list goes on. These products have
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| | cruciferous vegetables, but to get enough
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| become staples for many vegetarians and
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| | iodine.
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| vegans. So, the question of the safety of
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| | Conclusion : There is no evidence that
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| soy is one that certainly deserves
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| | eating soy foods regularly causes thyroid
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| serious consideration.
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| | problems in healthy people who include
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| Let's briefly address a few of the major
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| | sufficient iodine in the diet.
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| claims against soy. For more detailed
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| | Soy and Cognitive Function
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| information about each of these issues,
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| | Claim: Soyfoods, especially tofu, can
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| the following websites are most helpful:
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| | cause mental deterioration and accelerate
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| www.llu.edu//llu/vegetarian/soy2.html
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| | aging.
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| www.foodrevolution.org/what_about_soy.htm
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| | One study done in Hawaii (the Honolulu
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| | Heart Study) found that Japanese-American
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| www.soybean.com/drsuz.htm
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| | men who ate the most tofu in middle age
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| Soy and Breast Cancer
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| | had the greatest mental deterioration and
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| Claim : Soy increases risk of breast
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| | dementia as seniors. This study is widely
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| cancer.
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| | cited as evidence that tofu may cause a
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| Among the very first health claims made
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| | reduction in cognitive function.
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| for soy is that it may reduce incidence
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| | Interestingly, there have been at least
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| of breast cancer. It seemed so obvious
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| | three other studies that have suggested
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| when one compared the very low rates of
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| | that soy provides significant beneficial
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| breast cancer in Asian countries using
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| | effects on cognitive function. In
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| large amounts of soy with rates in North
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| | addition populations with relatively high
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| American countries that used
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| | soy intake (about a serving a day),
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| comparatively small amounts of soy. The
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| | including people in Asia and Seventh-day
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| risk reduction was thought to be due to
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| | Adventists, experience lower rates of
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| the isoflavones (mainly genestein and
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| | dementia than those populations who eat
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| daidzen) in soy. Isoflavones are a type
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| | little if any soy. While this does not
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| of phytoestrogen (plant estrogen) that
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| | prove that soy is beneficial, it does
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| has been thought to interfere with the
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| | suggest that moderate soy consumption is
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| ability of the potent human form of
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| | likely not detrimental.
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| estrogen to increase cell proliferation
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| | Conclusion. The weight of the evidence
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| and, therefore, cancer risk. However,
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| | suggests that soy may offer some benefits
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| studies have been mixed. While some do
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| | to cognitive function, although more
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| indeed show soy acting as an
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| | research is needed before firm
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| anti-estrogen, others suggest soy may act
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| | conclusions can be made on this issue.
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| as a weak estrogen itself, increasing
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| | What about soy versus rice milk? It all
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| cancer risk. Interestingly, some studies
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| | depends. If you are sensitive to soy or
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| have shown that while small amounts of
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| | use a lot of soy products, you may wish
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| genestein increase cell growth, large
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| | to use fortified rice milk. However, my
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| amounts inhibit it. Finally, there is
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| | preference is for soy – especially for
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| some evidence that women eating soy from
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| | children. Soy is a much richer source of
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| an early age (especially during puberty)
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| | high quality protein, vitamins and
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| do reduce their breast cancer risk, while
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| | minerals. It also contains isoflavones,
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| there seems to be less protection for
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| | which are protective for heart health and
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| those who begin to eat soy later in life.
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| | against osteoporosis. I think it tastes
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| | better too.
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