Dietary intake and plasma isoflavones are inversely associated with inflammatory markers in breast cancer survivors: A cross-sectional study

The role of isoflavones in breast cancer, particularly their relationship with inflammatory markers, remains underexplored. We hypothesized that higher intakes of soy and isoflavones are inversely associated with inflammatory markers in breast cancer survivors. This cross-sectional study included 432 breast cancer survivors (mean age: 52 years). We assessed dietary soy and isoflavone intake and measured plasma concentrations of isoflavones, high-sensitivity C-reactive protein (hsCRP), adiponectin, interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α. Generalized linear and logistic regression models were used to obtain adjusted least squares means (LSmeans) and odds ratios (ORs) for individual or combined (if associated with soy intake) inflammatory markers. Participants with higher soy and isoflavone intakes had lower hsCRP and IL-6 concentrations and higher adiponectin concentrations. The LSmeans (95% confidence intervals, CIs) of the lowest and highest quintiles of soy food intake were 0.71 (0.49, 0.96) and 0.52 (0.33, 0.73) for hsCRP (mg/L), and 0.42 (-0.08, 0.91) and -0.02 (-0.50, 0.46) for the combined scores of hsCRP and adiponectin. The OR (95% CI) comparing extreme quintiles of isoflavone intake was 0.43 (0.20, 0.94) for elevated hsCRP. When plasma isoflavone concentrations were examined in relation to the combined scores of hsCRP and IL-6, the OR (95% CI) comparing the extreme quintiles was 0.32 (0.12, 0.91). Our results suggest that dietary soy and isoflavone intake, as well as plasma isoflavone concentrations, are inversely associated with inflammatory markers in breast cancer survivors. These findings highlight the need for further research to better understand their clinical implications.