Composite Dietary Antioxidant Index is Inversely Associated with Carotid Intima-Media Thickness in Saudi Patients with Subclinical Atherosclerosis: A Case-Control Study

Background: While individual antioxidants have been linked to reduced cardiovascular risk, the association between overall dietary antioxidant intake and subclinical atherosclerosis remains unclear. Aim: To examine the association between Composite Dietary Antioxidant Index (CDAI) and Carotid Intima-Media Thickness (CIMT) as a marker of subclinical atherosclerosis. Methods: A case-control study was conducted among 210 Saudi adults (105 with subclinical atherosclerosis and 105 age- and sex-matched controls) recruited from internal medicine clinics at King Abdulaziz University Hospital. Dietary intake was assessed using a validated food frequency questionnaire. CDAI was calculated from energy-adjusted, standardized intakes of six antioxidants: vitamins A, C, E, manganese, selenium, and zinc. Anthropometric data, blood pressure, lifestyle factors, and medical history were collected via structured interviews and clinical measurements. CIMT was assessed bilaterally using high-resolution B-mode ultrasound. Statistical analyses included group comparisons, correlation tests, and multivariable regression adjusting for potential confounders. Results: CDAI was inversely associated with CIMT (β = −0.184, P < 0.01) after adjusting for age, sex, BMI, blood pressure, smoking, and physical inactivity. Participants in the highest CDAI quartile had significantly lower mean CIMT than those in the lowest quartile ( P < 0.05). Among CDAI components, only vitamin E intake was significantly lower in the subclinical atherosclerosis group ( P < 0.05). Conclusion: Higher dietary antioxidant intake, as assessed by CDAI, is associated with reduced CIMT and lower risk of subclinical atherosclerosis. Longitudinal studies are recommended to clarify causality and explore underlying mechanisms.