Phytoestrogens are plant-derived compounds with structural similarity to estradiol, the primary female sex hormone. They are found in foods such as soy, flaxseed, and some grains and vegetables. The primary classes of phytoestrogens are isoflavones (e.g., genistein, daidzein), lignans, and coumestans. Their use to support the reproductive system is based on their ability to bind estrogen receptors and exert weak estrogenic or antiestrogenic effects, depending on endogenous estrogen levels.

Scientific studies, particularly randomized controlled trials and meta-analyses, have evaluated phytoestrogens, especially soy isoflavones, for their impact on menopausal symptoms such as hot flashes, menstrual cycle regulation, and bone health. Some evidence suggests that phytoestrogens may modestly reduce the frequency and severity of hot flashes in menopausal women. There is also limited evidence for potential beneficial effects on menstrual regularity and bone density, though findings are inconsistent and often modest in magnitude.

While a moderate body of evidence supports phytoestrogen use for alleviating certain reproductive symptoms, results are variable, and efficacy is generally lower than conventional hormone replacement therapy. Safety profiles are favorable for most individuals, but concerns remain for those with estrogen-sensitive conditions. Overall, phytoestrogens are used based on both mechanistic plausibility and clinical findings, though the strength of evidence is moderate rather than strong.