For at least 5,000 years, soybeans have been a staple in the Asian diet, along with soybean food products like tofu, tempeh and miso. Due to their long history as a widely consumed food, soybeans are generally considered very safe to eat. But for people with certain medical conditions or who take some medications, soybeans and soy food products may pose some dangers. Soy in the form of supplements could pose further risks as well.
Identification
Soybeans are a member of the pea plant family and are rich in protein, fiber and many other nutrients. Soy is the only plant-derived food that contains all the essential amino acids like meats, and soybeans also contain the phospholipid called lecithin. Another key constituent found in soybeans is the phytoestrogen substance known as isoflavone. Soy isoflavones appear to affect the body's estrogen receptors to either increase or reduce the hormonal effects of estrogen in the body, according to the University of Pittsburgh Medical Center. Today, soy is also found in supplements that are usually standardized for their concentration of isoflavones.
Effects
People sometimes use dietary soy and soy supplements to help lower their cholesterol levels, prevent osteoporosis and hormone-related cancers, and ease menopausal symptoms. Sometimes, soy is recommended in alternative medicine for treating allergic rhinitis, osteoarthritis, ulcerative colitis, diabetes, hypertension and cyclic mastitis. No conclusive medical research has proven that consuming soybeans and soy food products or taking soy supplements help to prevent or treat any health condition, however. Additionally, soy is a common food allergen like milk, peanuts, wheat and eggs, which can produce sometimes life-threatening allergic reactions in some people. Soy protein may also cause side effects like bloating, constipation, diarrhea and nausea.
Dangers
Consuming substantial amounts of dietary soy or taking soy supplements could pose dangers for some people, particularly those who have impaired thyroid function or hypothyroidism, cautions the University of Pittsburgh Medical Center. Soy can directly impede the thyroid gland's function, because the isoflavones can reduce the iodine levels in the body, which in turn can cause the thyroid to not function properly. The isoflavones in soybeans could also reduce testosterone levels in men, which could potentially lead to infertility or erectile dysfunction, the University of Pittsburgh Medical Center adds. Soy poses dangers for people with kidney disease, because it contains higher concentrations of potassium and phosphorous than other protein sources like meats and fish, notes the University of Maryland Medical Center. Because soy isoflavones can either stimulate or suppress the effects of estrogen in the body, there are some questions about whether soy could actually stimulate the growth of hormone-sensitive cancer cells. Estrogen-sensitive breast cancer is of particular concern regarding soy isoflavones.
Drug Interactions
Soybeans and soy supplements can potentially interact negatively with certain medications. For example, the isoflavones in soy can inhibit the absorption of thyroid medication or thyroid hormone, as well as calcium, zinc and iron supplements, according to the University of Pittsburgh Medical Center. Soy isoflavones could also reduce the effects of tamoxifen or "Nolvadex," a medication used to treat breast cancer, warns the University of Maryland Medical Center. Soy may interfere with your absorption of the osteoporosis medication raloxifene ("Evista") as well.
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