Effects of high-oleic dietary interventions on cardiometabolic outcomes in adults: a GRADE-based systematic review and meta-analysis of randomized controlled trials

BACKGROUND: Diets rich in oleic acid have been proposed as a strategy to modify cardiometabolic risk. Evidence from randomized controlled trials (RCTs) remains inconsistent, particularly for glucose-related outcomes. To assess the effects of high-oleic dietary interventions compared with lower-oleic diets on lipid profiles, and glycemic indices in adults. METHODS: PubMed, Embase, Web of Science, and Scopus were searched from inception to July 2025 in accordance with PRISMA 2020 guidelines. RCTs were eligible if the intervention diet provided at least 70% of total fatty acids as oleic acid, justified based on prior monounsaturated fat intervention literature, and differed from the comparator by at least 5% points. Random-effects meta-analyses were performed using weighted mean differences. Certainty of evidence was evaluated using the GRADE framework with outcome-specific assessments reported in a Summary of Findings table. RESULTS: Twenty-six trials involving 1,244 participants were included. High-oleic diets were associated with modest reductions in total cholesterol (WMD: -0.14; 95% CI: -0.28 to -0.01; I2 = 80.8%), and LDL-C (WMD: -0.13; 95% CI: -0.24 to -0.03; I2 = 64.6%). No significant effects were observed for HDL-C, triglycerides, fasting blood glucose, fasting insulin, or HOMA-IR. Lipid-lowering effects were more evident in trials with higher oleic acid proportions (≥ 80%). CONCLUSIONS: High-oleic dietary interventions result in small but consistent improvements in selected lipid outcomes without effects on glycemic indices. Benefits are dose-dependent and most pronounced when oleic acid constitutes a substantial portion of dietary fat. Absolute changes are modest, highlighting the complementary role of high-oleic diets in cardiometabolic risk management.