Comparison of the five different definitions of equol producers: The relationship between blood and urine equol concentrations and blood parameters in 466 healthy men and women

Abstract

Background and aimsNo studies have compared various definitions of “equol producers” until now. Therefore, we aimed to explore the accuracy of five different definitions of equol producers (EQP) and their associations with health benefits. MethodsThis is a cross-sectional study of 466 healthy Japanese men and women aged between 22 and 88 years. Equol producer proportions were calculated from their serum and urine isoflavone concentrations using five commonly used definitions. We then examined their accuracy, and associations with the blood parameters. ResultsProportions of equol ranged from 29 % in the most stringent definition to 47.6 % in the most sensitive definition. EQP identified under all definitions had significantly low serum PSA11PSA: prostate specific antigen. levels compared to nonequol producers (NEQP). The most stringent definition, which is defined as the urinary equol level of 1.0 μM and above, corresponded to the highest median serum equol level and was associated with better health outcomes. Male EQP identified by this definition seemed to have reduced risk of LDL22LDL: low density lipoprotein-hypercholesterolemia by 50 %, and female EQP identified by this definition seemed to have lower risk of high hs-CRP,33CRP: C-reactive protein compared to NEQP. Both the first and second stringent definition, which is defined as the serum equol level of 1.0 ng/mL and above, was associated with lower thyroid stimulating hormone level. ConclusionsMore stringent definitions were associated with better parameters in general. Combined with the dietary inquires, a reliable definition for equol producer is crucial to evaluate the health benefits of equol.