Abstract
BACKGROUND: Chronic low-grade inflammation and insulin resistance are hallmark features of metabolic syndrome (MetS). The pathways through which healthy diets influence metabolic health outcomes remain unclear. METHODS: This study utilized six cycles (2005-2016) of cross-sectional data from the National Health and Nutrition Examination Survey (NHANES). A total of 10,518 adults (≥ 20 years) with complete data on diet, metabolic risk factors, and relevant covariates were included. Dietary live microbe intake was quantified and categorized into three groups-low, medium, and high- on the basis of estimated colony-forming units in foods, as well as by categorizing the consumption of foods with medium/high microbial content (MedHi). MetS was defined according to the National Cholesterol Education Program Adult Treatment Panel III criteria. Multivariate logistic regression, restricted cubic spline analyses, and mediation analyses were performed to examine the associations and potential mechanistic pathways via inflammation [white blood cell (WBC) counts, neutrophil counts, serum albumin, and systemic immune-inflammation (SII) index] and insulin resistance [triglyceride-glucose (TyG) index and homeostatic model assessment of insulin resistance (HOMA-IR)]. RESULTS: Compared with the non-MedHi group participants, the risk of MetS was 17% lower (odds ratio [OR]: 0.83, 95% confidence interval [CI]: 0.71, 0.98) in the high-MedHi food intake group. Compared with that of the low microbe food group, the risk of MetS was 16% lower (OR: 0.84, 95% CI: 0.72, 0.98) in the medium microbe food group. Mediation analysis indicated that the association between dietary live microbe intake and a reduced risk of MetS was mediated by improved systemic inflammation, but no significant mediating effect of insulin resistance was found. CONCLUSIONS: Moderately increasing the intake of foods rich in high level microbes in the daily diet is associated with a reduced risk of MetS and may have potential benefits for maintaining stable blood pressure and blood lipid levels. Systemic inflammation markers, including the serum neutrophil counts and SII, partially mediate the association between dietary live microbe intake and MetS.