S-Equol: The Bioactive Gut-Derived Isoflavone with Selective Estrogen Receptor-β Power

S-Equol is a unique gut-derived metabolite formed exclusively by intestinal bacteria from the soy isoflavone daidzein. Unlike its mirror image R-equol, only S-equol shows strong biological activity, exhibiting a remarkably high affinity for estrogen receptor-β—an important target for supporting hormonal balance, skin health, cognitive wellness, and metabolic resilience. Human studies confirm that S-equol is the naturally produced and bioavailable enantiomer, making it the key mediator of soy’s beneficial effects. Its selective receptor-β action allows gentle, targeted modulation without the overstimulation associated with estrogen receptor-α.

Source : https://pubmed.ncbi.nlm.nih.gov/15883431/