Composite dietary antioxidant index in predicting chronic kidney disease risk: Findings from NHANES 1999 - 2018

BACKGROUND: Chronic kidney disease (CKD) poses a significant global health burden, with oxidative stress implicated in its pathogenesis. The composite dietary antioxidant index (CDAI), integrating multiple dietary antioxidants, may offer a novel approach to CKD risk assessment, yet evidence remains limited. OBJECTIVE: This study aimed to evaluate the association between CDAI and CKD risk in a nationally representative U.S. MATERIALS AND METHODS: Cross-sectional data from 24,202 adults in NHANES (1999 - 2018) were analyzed. CDAI was calculated from six dietary antioxidants (vitamins A/C/E, zinc, selenium, β-carotene). CKD was defined by estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m² or UACR ≥ 30 mg/g. Multivariable logistic regression, restricted cubic splines (RCS), and subgroup analyses were employed to assess associations, adjusted for demographics, lifestyle, comorbidities, and laboratory parameters. RESULTS: Participants in the highest CDAI quartile (Q4) had a 27% lower CKD risk (adjusted OR = 0.73, 95% CI: 0.62 - 0.87, p < 0.001) vs. Q1, with a dose-dependent relationship (p-trend < 0.001). RCS revealed nonlinear effects, with steep risk reduction at CDAI < 10 and plateauing at CDAI > 20. Subgroup analyses showed stronger inverse associations in women, older adults (≥ 65 years), and individuals with diabetes or cardiovascular disease (p-interaction < 0.05). Mediation analysis indicated direct effects of CDAI, independent of traditional risk factors. CONCLUSION: Higher CDAI levels were independently associated with reduced CKD risk, particularly in high-risk subgroups. These findings support the potential role of dietary antioxidants in CKD prevention, warranting further prospective validation.