Dietary Inflammatory Index and Cardiovascular Disease Risk in Australian Adults: A Secondary Analysis of the OLIVAUS Trial

Background: The Dietary Inflammatory Index (DII®) is a commonly used tool to assess diet-related inflammation. Higher DII scores are associated with increased cardiovascular disease risk in large observational cohorts yet, controlled-trial evidence evaluating cardiovascular outcomes across DII levels is scarce. This secondary analysis examined cross-sectional differences and longitudinal associations between dietary inflammatory potential and cardiovascular outcomes in healthy Australian adults. Methods: In a double-blind randomised crossover trial, 50 participants consumed 60 mL/day of either high-phenolic (320 mg/kg) or low-phenolic (86 mg/kg) olive oil for two 3-week intervention periods, separated by a 2-week washout. Anthropometry (weight, height, waist circumference, BMI) and cardiovascular outcomes (i.e., blood pressure, lipids, oxidised LDL, and HDL-cholesterol efflux capacity) were measured at four timepoints. DII and energy-adjusted DII (E-DIITM) scores were calculated from 3-day food diaries at baseline and follow-up of each 3-week intervention phase. Linear mixed-effects models compared cardiovascular outcomes across DII tertiles (low, medium, high) adjusting for intervention, period, sequence, age, sex, and waist circumference. Results: Forty-three participants completed the study. At baseline, BMI, waist circumference, systolic blood pressure, total cholesterol, and LDL differed significantly across DII tertiles (p<0.05). Across the study period, cardiovascular outcomes did not differ between medium or high versus low DII tertiles, and no significant time-by-tertile interactions were observed (all p>0.05). DII values remained stable across timepoints, while E-DII decreased modestly within individuals in both intervention periods. Conclusions: In this healthy cohort, DII was not associated with adverse short-term changes in cardiovascular outcomes. Longer-duration studies with greater contrast in dietary inflammatory potential are warranted to clarify the relationship between DII and cardiovascular health.