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Isoflavones are chemical compounds found in soy and other plants that are phytoestrogens, or plant-derived estrogens. They have a chemical structure that is similar to the estrogens naturally produced by the body, but their effectiveness as an estrogen has been estimated to be much lower than true estrogens. Two types of isoflavones, genistein and daidzein, are found in soy beans, chick peas, and lentils, and are considered to be the most potent estrogens of the phytoestrogens. Still, the estrogen potency of phytoestrogens is estimated to be only 1/1000 to 1/100,000 of that of estradiol, natural estrogen.
Some studies have shown that these compounds can help relieve the symptoms of menopause, and many women do use soy products to help control the symptoms of menopause. In particular, women who have had breast cancer and do not want to take hormone therapy (HT) with estrogen sometimes use soy products for relief of menopausal symptoms. However, some phytoestrogens can actually have anti-estrogenic properties in certain situations, and the overall risks of these preparations have not yet been determined. For example, researchers have shown that long-term use of phytoestrogens in postmenopausal women led to an increase in endometrial hyperplasia (overgrowth of the tissues lining the uterus) which can be a precursor to cancer. Further research is needed to fully characterize the safety and potential risks of phytoestrogens.
There is also a perception among many women that these products are "natural" and therefore safer than HT, but this has never been proven scientifically. If you are experiencing uncomfortable symptoms of menopause, your doctor can help you decide what type of treatment is appropriate for your individual situation.
Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care
"Patient education: Nonhormonal treatments for menopausal symptoms (Beyond the Basics)"