Bone mineral density in US adults in relation to urinary isoflavone excretion: secondary analysis using the National Nutrition and Health Examination Survey (NHANES) data

Abstract

The NHANES provides a rich data source to efficiently evaluate correlates of health outcomes. Analysis of health in relation to objective measures of soy intake, such as urinary isoflavone concentrations, is challenged by differences in host intestinal bacterial profile. Some, but not all, individuals harbor bacteria capable of metabolizing the isoflavone daidzein to equol and O‐desmethylangolensin (ODMA). To assess the impact of controlling for daidzein excretion, associations of categorical and continuous measures of urinary equol, ODMA, daidzein, equol:daidzein, and ODMA:daidzein with bone mineral density (BMD) were evaluated in three NHANES data releases that were combined (1999–2004). Age‐ and sex‐adjusted total BMD in 3889 adults was positively associated with increasing quartiles of ODMA:daidzein (p=0.02) and ODMA concentration (p=0.01), but not with continuous ODMA:daidzein (p=0.38) and not as strongly with continuous ODMA concentration (p=0.08). BMD was positively associated with equol concentration (p<0.01), but not as strongly with quartiles of equol concentration (p=0.06). BMD was not associated with daidzein concentration or equol:daidzein. Additional analyses will evaluate BMD in relation to urinary isoflavone measures stratified by sex and race/ethnicity groups, and with all analyses stratified by categories of isoflavone intake calculated from the dietary interview.