^aNational Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA

Correspondence: Dr. Liza Valentín-Blasini, National Center for Environmental Health, Centers for Disease Control and Prevention, 4770 Buford Highway MS F-47, Atlanta, GA 30341, USA. Tel.: +1770-488-7902; Fax: +1770-488-0181; E-mail: LValentin@cdc.gov

Received 12 October 2004; Accepted 4 January 2005; Published online 1 June 2005.

Abstract

We report population-based urinary concentrations of phytoestrogens stratified by age, sex, and composite racial/ethnic variables. We measured the isoflavones — genistein, daidzein, equol, and O-desmethylangolensin (O-DMA) — and the lignans — enterolactone and enterodiol — in approximately 2500 urine samples from individuals aged 6 years and older who participated in the National Health and Nutrition Examination Survey (NHANES) in 1999 and 2000. We detected all phytoestrogens in over 70% of the samples analyzed; enterolactone was detected in the highest concentrations, and daidzein was detected with the highest frequency. The geometric means for each phytoestrogen were as follows: genistein, 22.3 g/g; daidzein, 68.6 g/g; equol, 7.65 g/g; O-DMA, 3.95 g/g; enterolactone, 217 g/g; and enterodiol, 24.3 g/g creatinine. The 95th percentiles for each phytoestrogen were as follows: genistein, 380 g/g; daidzein, 944 g/g; equol, 50.3 g/g; O-DMA, 217 g/g; enterolactone, 2240 g/g; and enterodiol, 240 g/g creatinine. Multivariate analyses showed statistically significant differences among many of the demographic subgroups. Adolescents had higher concentrations of genistein and equol than adults. Non-Hispanic whites had higher concentrations of enterodiol and equol than Mexican Americans or non-Hispanic blacks. Non-Hispanic whites also had higher concentrations of enterolactone and O-DMA than Mexican Americans. Mexican Americans had higher concentrations of genistein than non-Hispanic blacks; however, the opposite was found for O-DMA. Determination of phytoestrogen exposure in the US population will help us to better understand phytoestrogen consumption in the US and will assist us in elucidating the potential role of phytoestrogens in protecting against cancer and heart disease.