Association of dietary index for gut microbiota and cardiovascular diseases in American adults: evidence from National Health and Nutrition Examination Survey 1999–2018

Background: As a significant health burden, cardiovascular disease (CVD) contributes substantially to global disease and death rates. While the gut microbiota has been linked to CVD, its dietary influence remains unclear. The Dietary index for gut microbiota (DI-GM) evaluates diet-related impacts on microbiota diversity. This study explores the relationship between DI-GM and the risk of CVD. Methods: Using National Health and Nutrition Examination Survey (NHANES) data spanning 1999-2018, this cross-sectional study included 39,181 adults aged 20 years or older, among whom were individuals with CVD. DI-GM, based on dietary recall, was calculated to assess microbiota diversity. Multivariable weighted logistic regression explored the association between DI-GM and CVD, with trend tests, subgroup analyses, smoothed curves, and multiple imputation ensuring robustness. Mediation analysis examined the role of body mass index (BMI). Results: A total of 39,181 participants (mean age: 47.15 years) were included, with 49.18% female and 50.82% male. Higher DI-GM levels correlated with a decreased prevalence of CVD (DI-GM: OR = 0.95, 95% CI = 0.92-0.98). Compared to participants with DI-GM scores of 0-3, those with DI-GM ≥6 had significantly lower CVD risk (OR = 0.82, 95% CI = 0.71-0.94). Restricted cubic spline analysis showed a linear association between DI-GM and CVD. A significant mediating effect of BMI was observed (proportion of mediation: 16.27%, 95% CI: 9.11%-35.48%). Conclusions: An inverse association was found between the DI-GM index and CVD prevalence, where increased DI-GM scores corresponded to a lower CVD risk, partly mediated by reductions in BMI.