Association Between Nonalcoholic Fatty Liver Disease and the Dietary Index for Gut Microbiota: A Cross-Sectional...

Nonalcoholic fatty liver disease (NAFLD) is defined by excessive hepatic lipid deposition, which is markedly affected by dietary habits and gut microbiota. This study utilizes the Dietary Index for Gut Microbiota (DI-GM), an established tool derived from 106 peer-reviewed studies, to assess the effect of diet on NAFLD. By evaluating foods that modulate microbiota composition, the DI-GM offers a robust framework for examining dietary quality and its connection to NAFLD risk in a large population. This cross-sectional study analyzed data from the National Health and Nutrition Examination Survey (NHANES, 1999-2018) involving 101,316 participants, excluding those under 18, with incomplete data, alternative liver conditions, or excessive alcohol consumption. Finally, 5283 participants were included. NAFLD was identified using the United States Fatty Liver Index (USFLI). DI-GM scores were calculated from two 24-h dietary recall interviews. Multivariate logistic regression and restricted cubic splines (RCS) assessed the DI-GM-NAFLD relationship, adjusting for demographics, lifestyle, and medical history. Subgroup and sensitivity analyses ensured robustness, while ROC curves and DeLong's test compared DI-GM's predictive ability with Healthy Eating Index-2015 (HEI-2015) and Dietary Approaches to Stop Hypertension (DASH). Among 5283 participants, higher DI-GM scores were associated with a 23.8% lower NAFLD risk (OR: 0.762, 95% CI: 0.590-0.986) in the highest versus lowest quartile. RCS analysis confirmed a linear negative association (p < 0.001, p-nonlinearity = 0.209), which was consistent across subgroups (all p > 0.05). In addition, sensitivity analyses supported these findings. DI-GM showed a higher AUC (0.867) than HEI-2015 (0.848) and DASH (0.847; both p < 0.0001, DeLong's test). Elevated DI-GM scores are inversely linked to NAFLD risk, suggesting a potential link between dietary patterns that promote beneficial gut microbiota modulation and reduced liver disease risk. This highlights the potential of DI-GM-guided dietary interventions for NAFLD prevention. Nevertheless, additional studies are required to clarify the underlying mechanisms.