Pharmacokinetics of an Equol Supplement in Humans

Equol, a metabolite of daidzein, is considered to be the most effective estrogen modifier in the human body. The production of equol depends on an individual's intestinal flora, however, so an equol supplement has been developed for nonproducers. To examine the pharmacokinetics in humans of a newly developed equol supplement made from fermented soy germ by Lactococcus sp. Equol supplements were given to 18 adults (20-22 yr) in three doses (one 10-mg dose, one 30-mg dose, or three 10-mg doses per day) to investigate the pharmacokinetics and physiological effects. Equol reached a peak in plasma at 30 or 60 min after supplement intake, and the average plasma half-life was 83 min. Plasma concentrations of equol were always higher in females than in males. Less than 5% of the highest plasma concentration remained in the plasma after 2 days. Up to 56% of the orally administered equol was excreted in urine within 1 day. This short-term, high-dose equol exposure yielded no observable adverse effect in both feeling and biochemical markers. For equol nonproducers, this newly developed equol supplement may yield more beneficial effects of isoflavones.