isoflavones

Isoflavones are a class of phytoestrogens within the flavonoid family. They occur mainly in legumes, especially soybeans, and include the aglycones genistein, daidzein, and glycitein, as well as their glycoside forms such as genistin, daidzin, and glycitin. In foods, isoflavones are predominantly present as glycosides that are hydrolyzed to aglycones in the digestive tract.

They act as plant-derived estrogen-like compounds by binding to estrogen receptors, with differential affinity for ER alpha and ER beta. Isoflavones are often described as selective estrogen receptor modulators due to tissue-dependent effects. Gut microbiota converts daidzein to equol in some individuals, a metabolite associated with enhanced biological activity; absorption is followed by phase II metabolism (glucuronidation and sulfation).

Epidemiological and clinical studies have explored isoflavones for menopausal symptoms, osteoporosis, cardiovascular risk, and cancer. Evidence for hot flash relief is modest and inconsistent; some trials show small reductions. Observational data suggest possible protective effects against certain hormone-sensitive cancers in Asian populations, but randomized trials are inconclusive. Overall, dietary isoflavone intakes comparable to traditional soy-rich diets are considered safe for most people.

High-dose supplements may interact with thyroid function in iodine-deficient individuals, and may affect estrogen-sensitive tissues; use in pregnancy, lactation, or hormone-sensitive cancer patients should be discussed with a clinician. Dietary intake from soy foods is generally regarded as safe.

Main dietary sources are soy products: tofu, tempeh, soy milk, miso. Smaller amounts occur in chickpeas, lentils, and other legumes.