Phytoestrogen Properties of Soy
Soybeans and products made from them contain isoflavonoid phytoestrogens, chemicals that behave like the female hormone estrogen in the human body. Soy phytoestrogens may improve a person's cardiovascular health, reduce menopausal symptoms and improve bone health. Research studies find conflicting results when studying whether the phytoestrogens in soy increase a woman's risk for breast cancer.
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Types
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Soy isoflavonoid phytoestrogens activate in people who eat foods containing soybeans, soy supplements and other soy products. Eating edamame, a popular preparation of steamed soybeans, sometimes served salted and in their pods, nourishes the body with isoflavonoid phytoestrogens. Soy milk, tofu, vegetarian meat and cheese substitutes made with soy, and soy flour all supply phytoestrogens. As a substitute for or addition to eating soy-based foods, soy supplements in the form of capsules or powders supply phytoestrogens.
Significance
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Declining levels of the female hormone estrogen in post-menopausal women are responsible for the increasing risks of heart disease and osteoporosis women face as they age. Women going through menopause and experiencing lowered estrogen levels experience uncomfortable symptoms such as vaginal dryness and hot flashes. Unfortunately, a common treatment for these effects, post-menopause estrogen replacement therapy, increases the risk of breast cancer, Alzheimer's Disease, stroke, blood clots and other health conditions. Post-menopausal women supplement their diets with soy to avoid the side effects of hormone replacement therapy. Other women report an improvement in PMS symptoms and even breast growth while taking soy. Some evidence suggests soy as a boost for fertility.
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Effects
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Scientists do not fully understand the effects of soy phytoestrogens on a woman's body. According to the Cornell University Sprecher Institute for Comparative Cancer Research, studies report soy phytoestrogens both increasing and decreasing breast cancer risks. Research in both animals and humans suggests supplementation with soy improves cholesterol levels and artery function, possibly reducing the risk of heart disease. After menopause, the estrogen-like effect of soy may reduce a woman's risk of osteoporosis. Substituting soy protein for animal protein results in a lower-calorie diet, thereby encouraging weight loss.
Theories/Speculation
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Asian women who consume diets naturally high in soy products experience milder menopause symptoms and have lower rates of breast cancer than women in the United States. Those statistics cause researchers to investigate the potential benefits of soy on women's health. Scientists plan further study to confirm whether phytoestrogens improve health, and at what doses.
Warning
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Because of the estrogen-like effects, soy phytoestrogens may interact with estrogen-containing medicines such as hormone replacement therapy or the birth control pill. Check with a doctor before adding any dietary supplements. A woman who is pregnant or breast-feeding should not take soy phytoestrogens. Report any allergic reactions after eating soy products or taking soy supplements to a doctor. Breast cancer survivors should avoid soy supplements until further research rules out a link between soy and breast cancer risk. Men taking large doses of phytoestrogens may experience breast growth or lowered testosterone.
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