Association between the dietary index for gut microbiota and diabetes: the mediating role of phenotypic age and body mass index.

Objectives: The global prevalence of diabetes is continuously rising, and the gut microbiota is closely associated with it. The Dietary Index for Gut Microbiota (DI-GM) assesses the impact of diet on the microbiota, but its association with diabetes risk remains unclear. This study aims to investigate the association between DI-GM and the risk of diabetes and analyze the mediating roles of phenotypic age and body mass index (BMI).

Methods: Utilizing data from the National Health and nutrition examination survey (NHANES) 1999-2018, we included 17,444 adults aged 20 years and older. DI-GM (score range: 0-13) was calculated based on dietary recall. Diabetes was diagnosed based on laboratory results and self-reported information. Multivariable logistic regression was used to analyze the association between DI-GM and diabetes, adjusting for relevant covariates. Mediation analysis evaluated the roles of phenotypic age and BMI.

Results: After adjusting for confounders, higher DI-GM scores were significantly associated with a lower risk of diabetes (OR = 0.93, 95% CI = 0.90-0.96, p < 0.001). Compared to the group with DI-GM scores of 0-3, those with scores of 5 (OR = 0.76, 95% CI = 0.67-0.86) and ≥ 6 (OR = 0.77, 95% CI = 0.68-0.88) had significantly reduced diabetes risk. Phenotypic age and BMI accounted for 41.02 and 25.57% of the association between DI-GM and diabetes, respectively.

Conclusion: Higher DI-GM scores are associated with a lower risk of diabetes, partially mediated through reduced phenotypic age and BMI.