Association between the novel dietary index for gut microbiota and diabetic kidney disease among patients with diabetes: evidence from the NHANES

Emerging evidence suggests that gut microbiota-modulating dietary patterns may influence the development of diabetic kidney disease (DKD), but population-based evidence remains limited. This study aimed to investigate the associations between the Dietary Index for Gut Microbiota (DI-GM) and DKD in a nationally representative sample. We analyzed data from the National Health and Nutrition Examination Survey (NHANES), which included 5,560 adults with diabetes. The DI-GM was calculated on the basis of dietary components known to modulate the gut microbiota. DKD was defined by the urinary albumin-to-creatinine ratio or estimated glomerular filtration rate. Multivariate logistic regression, restricted cubic spline (RCS), and subgroup analyses were performed to assess associations while adjusting for sociodemographic, lifestyle, and clinical factors. Logistic regression analyses revealed that higher DI-GM scores were significantly associated with reduced DKD risk (adjusted OR = 0.96, 95% CI: 0.92–0.99). The RCS results demonstrated a nonlinear relationship between DI-GM and DKD, with a threshold effect at DI-GM = 5. When the DI-GM was < 5, no significant association was observed (OR = 1.04, 95% CI: 0.97–1.11; P = 0.31). However, when DI-GM was ≥ 5, each unit increase in DI-GM was associated with a 12% reduction in DKD risk (OR = 0.88, 95% CI: 0.81–0.95; P < 0.01). The association remained consistent across subgroups (all P-interaction > 0.05) and proved robust in sensitivity analyses accounting for missing data and additional clinical confounders. Our findings indicate a nonlinear association between the DI-GM and DKD risk. Specifically, a protective effect was observed only when the DI-GM reached a threshold of 5. These results suggest that maintaining a higher DI-GM score, particularly above 5, may be an effective dietary strategy to lower the risk of DKD in patients with diabetes.