Equol producing status, isoflavone intake, and breast density in a sample of US Chinese women
Menée à partir d'entretiens auprès de 224 femmes d'origine chinoise et âgées de 36 à 58 ans, cette étude américaine analyse, en fonction de la capacité de l'organisme à produire de l'équol (une phytoestrogène provenant de la dégradation de la daidzéine, une isoflavone), la relation entre la consommation d'isoflavones et la densité mammaire
Background : Differences in ability to metabolize daidzein to equol might help explain inconsistent findings regarding isoflavones and breast cancer. We examined equol producing status in relation to breast density, a marker of breast cancer risk, and evaluated whether an association of isoflavone intake with breast density differs by equol producing status in a sample of Chinese immigrant women. Methods : Participants were 224 women, age 36-58 years, enrolled in a study on diet and breast density. All women completed dietary recall interviews, underwent a soy challenge to assess equol producing status, and received a mammogram assessed for breast density using a computer-assisted method. Results : In our sample, 30% were classified as equol producers. In adjusted linear regression models, equol producers had significantly lower mean dense tissue area (32.8 vs. 37.7 cm2, p=0.03) and lower mean percent breast density (32% vs. 35%, p=0.03) than non-producers. Significant, inverse associations of isoflavone intake with dense area and percent density were apparent, but only in equol producers (interaction p=0.05 for both). Conclusions : These results support the possibility that equol producing status affects breast density, and that effects of isoflavones on breast density depend on ability to metabolize daidzein to equol. Impact : While these findings warrant confirmation in a larger sample, they offer a possible explanation for the inconsistent findings regarding soy intake and breast density and possibly also breast cancer risk. The findings further suggest the importance of identifying factors that influence equol producing status, and exploring appropriate targeting of interventions.