Abstract
BACKGROUND: Metabolic syndrome (MetS) poses a huge global public health challenge. The dietary index for gut microbiota (DI-GM) measures the influence of diets on the microbiome, but its link with the odds of MetS is elusive. This paper examined the link between DI-GM and MetS and investigated the mediating role of the dietary inflammatory index (DII). METHODS: Data were sourced from the 2007-2018 NHANES for adults diagnosed with MetS. A total of 20,999 participants were included in the analysis. Dietary data were recorded via two 24-h dietary recalls, from which DI-GM and DII were calculated. Multivariate weighted logistic regression and restricted cubic spline (RCS) analyses were leveraged to assess the link between DI-GM and MetS. Mediation analysis was implemented to determine the role of DII in this association. Subgroup and sensitivity analyses were also implemented. RESULTS: After adjusting for all covariates, participants in the highest DI-GM scores (Q4) had a greatly lower odds of MetS compared to those in the lowest DI-GM group (Q1) (OR = 0.80, 95% CI = 0.69-0.92, p = 0.003). The RCS analysis noted a linear negative link between DI-GM and MetS (P for nonlinear = 0.414). DII partially mediated the correlation between DI-GM and MetS [Indirect effect estimate = -0.00265, 95% CI: (-0.00445, -0.00167), p < 0.001]. Subgroup analysis showed consistent negative associations between higher DI-GM (Q4) and MetS across various demographic and lifestyle subgroups, with no statistically significant interactions observed (P interaction > 0.05). CONCLUSION: High DI-GM levels are linked with a significantly reduced odds of MetS, with DII partially mediating this association.