What is soy isoflavones?
Soy isoflavones belong to a class of plant-based compounds known as phytoestrogens, so-called because they are similar in chemical structure and function to the female sex hormone estrogen. Soy isoflavones occur naturally in soybeans and can be found in several soy-based foods such as miso, soy sauce, tofu, edamame, soy milk and soy butter. Researchers have found that these compounds have some medicinal properties, particularly for women, and continue to study soy isoflavones for other health benefits.
Isoflavones are polyphenolic compounds that are capable of exerting estrogen-like effects. For this reason, they are classified as phytoestrogens—plant-derived compounds with estrogenic activity . Legumes, particularly soybeans, are the richest sources of isoflavones in the human diet. In soybeans, isoflavones are present as glycosides (bound to a sugar molecule). Fermentation or digestion of soybeans or soy products results in the release of the sugar molecule from the isoflavone glycoside, leaving an isoflavone aglycone. Soy isoflavone glycosides are called genistin, daidzin, and glycitin, while the aglycones are called genistein, daidzein, and glycitein (chemical structures of isoflavone aglycones).
How to work by Soy isoflavone?
Soy isoflavones are known to have weak estrogenic or hormone-like activity. Estrogens are signaling molecules that exert their effects by binding to estrogen receptors within cells (chemical structures of endogenous estrogens). The estrogen-receptor complex interacts with DNA to change the expression of estrogen-responsive genes. Estrogen receptors are present in numerous tissues other than those associated with reproduction, including bone, liver, heart, and brain . Soy isoflavones and other phytoestrogens can bind to estrogen receptors, mimicking the effects of estrogen in some tissues and antagonizing (blocking) the effects of estrogen in others . Scientists are interested in the tissue-selective activities of phytoestrogens because anti-estrogenic effects in reproductive tissue could help reduce the risk of hormone-associated cancers (breast, uterine, and prostate), while estrogenic effects in other tissues could help maintain bone density and improve blood lipid profiles (cholesterol levels). The extent to which soy isoflavones exert estrogenic and anti-estrogenic effects in humans is currently the focus of considerable scientific research.
Soy isoflavones and their metabolites also have biological activities that are unrelated to their interactions with estrogen receptors . By inhibiting the synthesis and activity of certain enzymes involved in estrogen metabolism, soy isoflavones may alter the biological activity of endogenous estrogens and androgens . Soy isoflavones have also been found to inhibit tyrosine kinases , enzymes that play critical roles in the signaling pathways that stimulate cell proliferation.
Both isoflavones and estrogen bind to and activate estrogen receptors (ERs) on cells. Human cells have two types of these receptors–ER-alpha and ER- beta—which have different distributions in different tissues. That doesn’t matter to estrogen, which happily binds to either type, but isoflavones are more finicky. They much prefer ER-beta. It’s an important distinction, because the two types of receptors produce different—sometimes completely opposite—effects.
As a result—while estrogen always acts like estrogen—isoflavones function differently in different tissues. They may have estrogen-like effects or anti-estrogenic effects, or no effects at all. For this reason, isoflavones are considered to be SERMs, or selective estrogen receptor modulators.
Their selective nature makes some SERMs useful in medical therapy. For example, while estrogen therapy can protect bone health in postmenopausal women, it may also raise risk for breast cancer. In contrast, the osteoporosis drug raloxifene—which is a SERM—has estrogen-like effects on bones, but anti-estrogenic effects in breast tissue. So it helps protect bone without raising breast cancer risk.
Benefits of taking soy isoflavones supplements:
Soy isofalvones have distinctive curative effect for treating breast carcinoma, women’s climacteric syndrome, prostate cancer, heart disease, cardio vascular vessel disease and osteoporosis.
Soybean isoflavones are representative plant estrogen. It can replace estrogen and combine with ER to exert estrogen function. The estrogen function of soybean isoflavones have defending and treating effect to blood fat hoist, atherosclerosis and osteoporosis which are arosed by old lady’s hormone retreat.
A U.S.-Chinese research team conducted a large-scale study to determine what, if any, effect the consumption of soy-based foods would have on the risk of recurrence among breast cancer survivors. Researchers assembled a study group of more than 9,500 U.S. and Chinese women who had survived invasive breast cancer. The research team monitored and measured the women’s intake of soy isoflavones over the course of more than seven years. At the end of the study period, they found that soy isoflavone intake significantly reduced the risk of breast cancer recurrence and also slightly lowered the risk of breast cancer mortality, but at a rate considered statistically insignificant. Researchers published their findings in the July 2012 issue of “The American Journal of Clinical Nutrition.”
Endocrinology researchers at China’s Sichuan University analyzed data from a number of previous studies to assess the effects of regular soy isoflavone intake on the prevention of osteoporosis in women. They found that women who took soy isoflavone supplements on a regular basis showed a 54 percent increase in bone mineral density. They also reported that regular isoflavone intake was associated with a significantly lower level of bone resorption, the process by which older bone is broken down and its constituent minerals transported back into the bloodstream. Results of their meta-analysis were published in the March 2012 issue of “Asia Pacific Journal of Tropical Medicine.”
Because of their chemical similarity to the female sex hormone estrogen, soy isoflavones provide an alternative for postmenopausal women who cannot tolerate conventional hormone replacement therapy for a variety of reasons. In a study of isoflavones’ effectiveness in treating menopausal symptoms, researchers at Italy’s University of Catania came up with mixed results. While the soy isoflavones produced a 40 percent reduction in vasomotor symptoms, such as hot flashes, and a lower incidence of insomnia and depression, they had little, if any, effect on menopause’s musculoskeletal pains and vaginal dryness. Results appeared in the February 2012 issue of “Minerva Ginecologica.”
Two pharmacology researchers at the University of Southern California undertook a review of existing scientific literature about the impact of soy isoflavone supplementation on cognitive function. Their review covered eight 2000-2007 studies, including seven that were restricted to postmenopausal women. Of these studies, four indicated isoflavones had positive effects on cognitive function, while the other four were either equivocal or showed no significant benefit from soy isoflavones. Researchers attributed the conflicting conclusions of the studies to a variety of factors, including variations in the makeup of isoflavone intervention and the heterogeneity of study populations. In view of the indications that isoflavones may help improve cognitive function, researcher called for a carefully designed clinical study based on a standardized supplement. Writing in the November 2007 issue of “Expert Review of Neurotherapeutics,” they said such a study, conducted among a well-characterized study population, should enable researchers to reach a clinical consensus.
Side effects and safety of soy isoflavones
Consuming soy foods such as soy protein is LIKELY SAFE. Taking soy dietary supplements also seems to be safe for most people when used short-term (up to six months). Soy can cause some mild side effects such as constipation, bloating, and nausea. It can also cause allergic reactions involving rash and itching in some people.
Dosage of soy isoflavones supplement:
As doses of concentrated soy isoflavone providing 50-120 mg/day.