Abstract
BACKGROUND: Soy and some of its constituents, such as isoflavones, have been shown to affect the inflammatory process in animal studies. The association between soy food intake and inflammatory markers has not been evaluated adequately in humans. OBJECTIVE: Our aim was to evaluate whether higher intake of soy foods was inversely associated with inflammatory markers in 1,005 middle-aged Chinese women. DESIGN: In this cross-sectional study, dietary intake of soy foods was assessed by a validated food frequency questionnaire and by a 24-hour recall when biospecimens were procured. A general linear model was used to estimate the geometric means of selected inflammatory markers, including interleukin-6 (IL-6), IL-1β, tumor necrosis factor-α (TNFα), soluble IL-6 receptor, soluble GP130, soluble TNF receptors 1 and 2, and C-reactive protein, across categories of soy food intake after adjusting for age, lifestyle and dietary factors, and history of infectious or inflammation-related diseases. RESULTS: We found that multivariable-adjusted geometric mean concentrations of IL-6 and TNFα were inversely associated with quintiles of soy food intake, with a difference between the highest and lowest quintiles of 25.5% for IL-6 (P for trend=0.008) and 14% for TNFα (P for trend=0.04). Similar inverse associations were found for TNFα (P for trend=0.003), soluble TNF receptor 1 (P for trend=0.01), soluble TNF receptor 2 (P for trend=0.02), IL-1β (P for trend=0.05), and IL-6 (P for trend=0.04) when soy food consumption was assessed by the frequency of consumption in the preceding 24 hours. No significant associations were found for other markers studied. CONCLUSIONS: This study suggests that soy food consumption is related to lower circulating levels of IL-6, TNFα, and soluble TNF receptors 1 and 2 in Chinese women.