Inadequate Dietary Fibre Intake in Cardiovascular Disease Populations and Its Adverse Impact on Metabolic Health and...

Despite the established benefits of dietary fibre for cardiovascular health, it remains unclear whether and how dietary fibre intake, particularly from specific food sources, influences all-cause and cause-specific mortality in populations with established cardiovascular disease (CVD). This cohort study utilised data from the National Health and Nutrition Examination Survey 2003-2018. First, we compared dietary fibre intake between 3952 CVD individuals and 3952 age- and gender-matched non-CVD controls, generated by propensity score matching. Second, Cox proportional hazards regression models were employed to assess the associations of dietary fibre intake and source with all-cause, cardiovascular and cancer mortality in CVD populations. Third, to explore potential underlying mechanisms, we examined the associations of dietary fibre intake with validated biomarkers of metabolic health (triglyceride-glucose index, cardiometabolic index) and systemic inflammation (systemic inflammatory response index, systemic immune-inflammation index) in CVD populations. Adjustments were made for sociodemographic, dietary and health-related covariates. Compared to non-CVD individuals, CVD individuals had significantly lower average dietary fibre intake (15.7 g/day vs. 14.1 g/day, p < 0.001). Individuals with multiple coexisting CVDs exhibited the lowest dietary fibre intake (13.1 g/day). Only 9.3% of males and 11.7% of females met the recommended Adequate Intake standards (30 g/day for males, 21 g/day for females) in the CVD group. Over a median follow-up of 6.3 years, dietary fibre intake was inversely associated with all-cause, cardiovascular and cancer mortality in CVD populations. Compared to the first quartile, the all-cause mortality risk was reduced by 42% (hazard ratio [HR] 0.58, 95% confidence interval [CI] 0.45-0.75), cardiovascular mortality by 52% (HR 0.48, 95% CI 0.29-0.78) and cancer mortality by 50% (HR 0.50, 95% CI 0.24-1.02) in the fourth quartile of dietary fibre intake. In terms of dietary fibre sources, grain and legume/nut fibre had a stronger association with survival benefits than fruit and vegetable fibre. Mechanistic exploration analysis suggests that dietary fibre intake was associated with a decrease in triglyceride-glucose index and cardiometabolic index, but not with the systemic inflammation response index and systemic immune-inflammation index. Both CVD and non-CVD populations exhibited inadequate dietary fibre intake, with the deficiency being more pronounced in the CVD group. Among CVD populations, those with higher dietary fibre consumption had a lower risk of all-cause, cardiovascular and cancer mortality. Our findings highlight a significant and remediable nutritional gap in this high-risk population and underscore the importance of improving dietary fibre intake as a potential supplementary strategy to improve survival in adults with CVDs.