The effect of oleic acid enriched diets on glucose and lipid metabolism: a systematic review and meta-analysis

High-oleic diets (HODs), have been proposed to improve lipid and glucose metabolism, yet clinical evidence remains inconsistent. This systematic review and meta-analysis aimed to quantitatively evaluate the effects of HODs compared with low-oleic diets (LODs) on lipid profiles, apolipoproteins, and glucose homeostasis in adults. Following PRISMA 2020 guidelines, PubMed, Web of Science, Scopus, and Embase were searched from inception to September 2025. Randomized controlled trials (RCTs) in adults were included if the intervention provided ≥ 70% oleic acid of total fatty acids and differed from control diets by ≥ 5% points in oleic acid content. Data were pooled using random-effects models to estimate weighted mean differences (WMDs) with 95% confidence intervals (CIs). Twenty-six RCTs (n = 1,244 participants) met the inclusion criteria. Compared with LODs, HODs significantly reduced total cholesterol (WMD: −0.13 mmol/L; 95% CI: −0.24 to − 0.01) and low-density lipoprotein cholesterol (LDL-C) (WMD: −0.11 mmol/L; 95% CI: −0.20 to − 0.01) and modestly increased Apo A1 (WMD: 0.02 mmol/L; 95% CI: 0.00 to 0.03). No significant changes were observed for high-density lipoprotein cholesterol (HDL-C), triglycerides, very low-density lipoprotein cholesterol (VLDL-C), Apo B, and glucose metabolism. Subgroup and meta-regression analyses indicated stronger lipid-lowering effects when ≥ 80% of total fatty acids were oleic acid. Also, low heterogeneity was reported for most variables. High-oleic dietary interventions modestly improve circulating lipid profiles, particularly total and LDL cholesterol, without adverse effects on glucose metabolism. The proportion of oleic acid intake appears to be a key determinant of metabolic benefit.