Phytoestrogens

ContextSoy is the main source of phytoestrogens, which has long been used as traditional food. One major subtype of phytoestrogens includes isoflavones and they are scientifically validated for their beneficial actions on many hormone-dependent conditions.ObjectiveThe present study examines the effect of soy isoflavones on letrozole-induced polycystic ovary syndrome (PCOS) rat model.Materials and methodsPCOS was induced in Sprague-Dawley rats with of 1 mg/kg letrozole, p.o. once daily for 21 consecutive days. Soy isoflavones (50 and 100 mg/kg) was administered for 14 days after PCOS induction. Physical parameters (body weight, oestrous cycle determination, ovary and uterus weight) metabolic parameters (oral glucose tolerance test, total cholesterol), steroidal hormone profile (testosterone and 17β-oestradiol), steroidogenic enzymes (3β-hydroxy steroid dehydrogenase (HSD) and 17β-HSD), oxidative stress and histopathology of ovary were studied.ResultsSoy isoflavones (100 mg/kg) treatment significantly altered the letrozole-induced PCOS symptoms as observed by decreased body weight gain (p DiscussionTreatment with soy isoflavones exerts beneficial effects in PCOS rats (with decreased aromatase activity) which might be due to their ability to decrease testosterone concentration in the peripheral blood.ConclusionAnalysis of physical, biochemical and histological evidences shows that soy isoflavones may be beneficial in PCOS.

Dietary phytoestrogens are bioactive compounds with estrogenic activity. With the growing popularity of plant-based diets, the intake of phytoestrogen-rich legumes (especially soy) and legume-derived foods has increased. Evidence from preclinical studies suggests these compounds may have an effect on hormones and health, although the results of human trials are unclear. The effects of dietary phytoestrogens depend on the exposure (phytoestrogen type, matrix, concentration, and bioavailability), ethnicity, hormone levels (related to age, sex, and physiological condition), and health status of the consumer. In this review, we have summarized the results of human studies on dietary phytoestrogens with the aim of assessing the possible hormone-dependent outcomes and health effects of their consumption throughout a lifespan, focusing on pregnancy, childhood, adulthood, and the premenopausal and postmenopausal stages. In pregnant women, an improvement of insulin metabolism has been reported in only one study. Sex hormone alterations have been found in the late stages of childhood, and goitrogenic effects in children with hypothyroidism. In premenopausal and postmenopausal women, the reported impacts on hormones are inconsistent, although beneficial goitrogenic effects and improved glycemic control and cardiovascular risk markers have been described in postmenopausal individuals. In adult men, different authors report goitrogenic effects and a reduction of insulin in non-alcoholic fatty liver patients. Further carefully designed studies are warranted to better elucidate the impact of phytoestrogen consumption on the endocrine system at different life stages.

Phytoestrogens are plant-derived polyphenols with a structure similar to human estrogens. The three main groups of phytoestrogens, isoflavones, ellagitannins, and lignans, are transformed into equol, urolithins, and enterolignans, respectively, by bacteria. These metabolites have more estrogenic/antiestrogenic and antioxidant activities than their precursors, and they are more bioavailable. The aim of this study was to analyze the metabolism of isoflavones, lignans and ellagitannins by gut microbiota, and to study the possible correlation in the metabolism of these three groups of phytoestrogens. In vitro fermentation experiments were performed with feces samples from 14 healthy adult volunteers, and metabolite formation was measured by HPLC-PAD and HPLC-ESI/MS. Only the microbiota of one subject produced equol, while most of them showed production of O-desmethylangolensin (O-DMA). Significant inter-subject differences were observed in the metabolism of dihydrodaidzein and dihydrogenistein, while the glucoside isoflavones and their aglycones showed less variability, except for glycitin. Most subjects produced urolithins M-5 and E. Urolithin D was not detected, while uroltithin B was found in half of the individuals analyzed, and urolithins A and C were detected in two and four subjects, respectively. Enterolactone was found in all subjects, while enterodiol only appeared in five. Isoflavone metabolism could be correlated with the metabolism of lignans and ellagitannins. However, the metabolism of ellagitannins and lignans could not be correlated. This the first study where the metabolism of the three groups together of phytoestrogen, isoflavones, lignans, and ellagitannins by gut microbiota is analyzed.

Menopause is characterized by a decline in estrogen levels, leading to symptoms such as vasomotor instability, osteoporosis, and increased cardiovascular and cognitive risk. Hormone replacement therapy (HRT) remains the gold standard for managing menopausal symptoms; however, concerns regarding its long-term safety, including elevated risks of cancer and cardiovascular events, have prompted interest in alternative therapies. Phytoestrogens, particularly the isoflavones daidzein and genistein, are plant-derived compounds structurally similar to 17β-estradiol (E2) and capable of binding estrogen receptors. Found abundantly in soybeans and red clover, these compounds exhibit selective estrogen receptor modulator (SERM)-like activity, favoring ERβ over ERα, which underlies their tissue-specific effects. In vitro, in silico, and in vivo studies demonstrate their ability to modulate estrogenic pathways, inhibit oxidative stress, and influence reproductive and neurological function. Clinical trials show that daidzein and genistein, especially in equol-producing individuals, can reduce vasomotor symptoms such as hot flashes and night sweats. While results across studies vary, consistent findings support their safety and modest efficacy, particularly for women unable or unwilling to use HRT. Pharmacokinetic studies reveal moderate bioavailability and interindividual variability due to gut microbiota metabolism. At dietary levels, these compounds are generally safe, although high-dose supplementation is discouraged in individuals with hormone-sensitive cancers. Emerging evidence suggests lifelong consumption of soy-based foods may reduce cancer risk. In conclusion, daidzein and genistein represent promising, well-tolerated natural alternatives to conventional HRT, offering symptom relief and additional health benefits. Further research is warranted to optimize dosing, improve clinical outcomes, and clarify long-term safety in diverse populations, particularly with genetic variations in isoflavone metabolism.