Urinary soy isoflavone excretion is associated with favorable cardiometabolic risk markers in pregnant US women: Nhanes, 2001-2008

Introduction: Prior evidence suggests that phytoestrogens such as soy derived isoflavones may have beneficial effects on cardiovascular health and glycemic control. These data are mainly limited to postmenopausal women and individuals at elevated cardiometabolic risk. Because plasma estrogen concentrations rise during pregnancy and are thought to alter lipid and glucose metabolism, it is important to understand whether soy isoflavones are associated with markers of lipid and glucose metabolism in pregnant women. Methods: We analyzed data from 299 pregnant women who participated the 2001-2008 NHANES for whom 24-hour dietary recall, food frequency questionnaire, urinary isoflavone concentrations, and cardiometabolic risk biomarker measures were available. We examined urinary concentrations of isoflavones and metabolites in relation to cardiometabolic risk markers, adjusted for BMI, pregnancy trimester, total energy intake, and demographic and lifestyle factors. Results: Self-reported soy intake was positively correlated with urinary isoflavone and its metabolite concentrations (r = 0.21, P=0.02 for total isoflavones; r = 0.18, P=0.04 for O-DMA; r = 0.23, P=0.01 for equol). There was a significant, negative relationship between urinary isoflavone concentrations and cardiometabolic risk markers: comparing women in the highest versus lowest quartiles of total isoflavone excretion, multivariate-adjusted fasting glucose concentrations were 79.7 versus 89.8 mg/dL (P for trend=0.001). These figures were 10.3 versus 21.2 μU/mL (P for trend=0.03) for fasting insulin concentrations, and 2.1 versus 5.1 (P for trend=0.03) for HOMA-IR. The associations between isoflavone markers and blood lipid levels did not reach significance level. Discussion: Soy intake may have favorable effects on insulin sensitivity in pregnant women.