Demographic, anthropometric, and lifestyle factors and dietary intakes in relation to daidzein-metabolizing phenotypes among premenopausal women in the United States.

BACKGROUND The soy isoflavone daidzein is metabolized to equol and O-desmethylangolensin (ODMA) by intestinal bacteria in approximately 30-50% and 80-90% of persons, respectively. Studies suggest beneficial health effects associated with daidzein-metabolizing phenotypes; thus, assessing their determinants is an important goal. OBJECTIVE We evaluated relations between daidzein-metabolizing phenotypes and demographic, anthropometric, lifestyle, and dietary factors among premenopausal women in the United States. DESIGN Two hundred women provided a first-void urine sample after a 3-d soy challenge and completed a health and demographics questionnaire, physical activity questionnaire, food-frequency questionnaire, and 3-d food record. Urine samples were measured for isoflavones by gas chromatography-mass spectrometry to determine daidzein-metabolizing phenotypes. RESULTS Fifty-five (27.5%) and 182 (91%) women had detectable concentrations of urinary equol and ODMA (>87.5 ng/mL), respectively, and were classed as producers of these metabolites. Compared with nonproducers, equol producers were more likely (P < or = 0.05) to be Hispanic or Latino, to be highly educated, and to have frequent constipation, and ODMA producers were taller and less likely to be Asian than white. Equol and ODMA producers reported higher overall physical activity than did nonproducers. CONCLUSIONS We observed associations between equol production and ethnicity, education, constipation, and physical activity and between ODMA production and race, height, and physical activity. Associations with race and ethnicity were based on small numbers of Asian and Hispanic or Latino women, and confirmation of these findings is needed. Few dietary factors, assessed with the use of either a food-frequency questionnaire or food record, were associated with daidzein-metabolizing phenotypes.