Association Between Daily Dietary Vitamin C Intake and Heart Failure in Hypertensive Individuals Aged 50 Years and Above: NHANES 2003–2020

Background: Vitamin C, a dietary antioxidant, may influence the risk for cardiovascular disease. This investigation aimed to examine the association of daily dietary vitamin C intake with heart failure (HF) risk among hypertensive individuals aged ≥50 years. Methods: We analyzed 7901 hypertensive individuals (aged ≥50 years) from the National Health and Nutrition Examination Survey (NHANES) (2003–2020). Dietary vitamin C intake was quantified via two 24-hour diet recalls and stratified into quintiles. Logistic regression models were utilized to examine the link between vitamin C intake and HF risk, yielding data in odds ratios (OR) and 95% confidence intervals (CI). Restricted cubic spline (RCS) and stratification were executed to evaluate dose-response relationships and heterogeneity. Results: Individuals in the highest vitamin C quintile (≥127.15 mg/day) demonstrated 62% elevated OR versus the lowest quintile (<28.55 mg/day; OR = 1.62, 95% CI: 1.06–2.48, p = 0.030), with a significant linear trend across quintiles (trend test p = 0.015). RCS analysis confirmed a linear dose-response pattern of vitamin C intake with HF risk (p for overall = 0.002, p for nonlinear = 0.134). Exploratory subgroup analyses identified significant associations among males (p = 0.027), non-Hispanic Whites (p = 0.029), high school graduates (p = 0.019), married individuals (p = 0.011), never smokers (p = 0.008), non-alcohol consumers (p = 0.005), and those with diabetes mellitus (DM) (p = 0.002) or hyperlipidemia (p = 0.035). Associations were also significant for individuals in the highest body mass index (BMI) quintile (p = 0.004), the lowest age tertile (p = 0.004), the highest poverty-to-income ratio (PIR) quintile (p = 0.021), the highest urinary albumin-to-creatinine ratio (UACR) quintile (p = 0.033), and both the lowest (p = 0.028) and highest (p = 0.014) estimated glomerular filtration rate (eGFR) quintiles, with no significant interactions across these subgroups. After further adjustments to the micronutrients in the diet and the prescription of antihypertensive drugs, this clear association became no longer significant. However, the continuous model still has statistical significance. Conclusion: Higher dietary vitamin C intake was positively linked to an increased probability of HF in hypertensive individuals aged 50 years and above. Our findings provide a foundational framework for recommending dietary vitamin C intake for HF prevention in high-risk groups ≥50 years.