Soybeans, and the products made from them such as tofu, soy flour, soymilk, tempeh and miso, are wholesome foods that not only supply essential nutrients in the diet but also contain non-nutritive substances that may help fight certain types of disease. Though not quite the "miracle food" they were once thought to be, soybeans are still a valuable source of vegetarian protein and other nutrients, and may potentially help some people improve their health and alleviate symptoms of disease.
Good Nutrition
Soybeans are an excellent source of protein, vitamins, minerals, fiber and another type of substance found in plant foods known as phytochemicals, which are thought to play an active role in preventing or treating chronic diseases. The significant phytochemicals in soybeans are isoflavones, which can help reduce the risk of developing heart disease and certain cancers, and may help improve bone health.
Heart Protection
In 1999, the FDA approved a health claim on most soy product labels stating that 25 grams of soy protein a day may help lower the risk of heart disease. To carry this claim, a food must provide at least 6.25 g of soy protein per serving and be low in saturated fat, cholesterol and sodium.
The heart health claim is based on earlier scientific evidence that eating at least 25g a day of soy protein instead of animal protein significantly lowers cholesterol. A more recent survey and assessment of evidence published in a 2006 issue of the journal Circulation found that the average reduction in cholesterol was only about 3 percent. Soy is still considered a heart-healthy food because it is high in healthful polyunsaturated fats and low in dangerous saturated fats, and because it contributes vitamins and fiber to the diet.
Cancer Protection
Soy has been positively associated with hormone-related cancers such as breast and prostate cancers, but there is conflicting evidence that eating more soy foods will reduce the risk of developing or dying from any of these cancers.
Researchers at Vanderbilt University School of Medicine, who analyzed the results of large-scale breast cancer studies and the diets of the participants, found that a high consumption of soy foods during adolescence could help reduce the risk of developing breast cancer in later years.
Although there is no clear evidence that soy lowers the risk of developing prostate cancer, several clinical trials have indicated that soy may slow down the progression of protein-specific antigen (PSA), a blood marker associated with prostate tumor growth.
Bone Health
A review of nine studies linking soy isoflavones to bone health, published in a 2008 issue of the European Journal of Clinical Nutrition, found that people who consume more isoflavones lose significantly less bone and grow more new bone tissue than people who don't, indicating that eating soy foods may help prevent the bone-thinning disease osteoporosis that is especially common in post-menopausal women.
Menopausal Relief
Early studies indicated that, because of their hormonal effect, certain isoflavones in soy could help reduce symptoms of menopause, such as hot flashes. A 2004 review of subsequent studies found that soy foods have little effect on hot flashes or other symptoms for most women but may provide some relief for some.
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