URINARY EQUOL EXCRETION WITH A SOY CHALLENGE - INFLUENCE OF HABITUAL DIET

Equol is an isoflavonoid phytoestrogen produced from the soy isoflavon e daidzein by gut microflora. Not all humans produce equol from daidze in, presumably due to differences in colonic bacterial populations amo ng individuals, Previously, smaller studies reported that approximatel y 30% of participants excreted equol when consuming soy. The purpose o f our study was to determine the prevalence of equol excreters in a la rger sample and to examine what dietary components might influence the tendency to be an equol excreter. Thirty men and thirty women consume d a soy protein beverage containing 22 mg genistein and 8 mg daidzein for 4 days as a supplement to their habitual diets. The mean daily nut rient content of their habitual intakes was determined from 4-day food records. On Day 4, participants provided a 24-hour urine collection. Urinary isoflavonoid (genistein, daidzein, equol, and O-desmethylangol ensin) excretion was measured by gas chromatography-mass spectrometry. Twenty-one of the 60 participants (35%) excreted equol (> 2000 nmol/d ay) after 3 days of consuming the soy supplement. Daily equol excretio n ranged from 2,134-20,301 nmol/day in the excreters and 21-233 nmol/d ay in the nonexcreters. There was no difference in equol excreter prev alence between men (43%) and women (27%). Daily excretion of daidzein, genistein, and O-desmethylangolensin was similar between equol excret ers and nonexcreters and between men and women. Among the women, equol excreters consumed a significantly higher percentage of energy as car bohydrate and greater amounts of plant protein and dietary fiber, both as soluble and insoluble fiber compared to nonexcreters. Such differe nces were not observed in the men, who overall had significantly highe r fiber intakes than the women. These data suggest that, among women, dietary fiber or other components of a high-fiber diet may promote the growth and/or the activity of bacterial populations responsible for e quol production in the colon.