Impact of Heated Versus Unheated Cooking Oil on Postprandial Vascular Function and Metabolism

The impact of repeated heating of seed-based culinary oils on cardiometabolic health has not been well established. Heating oils to high temperatures (> 150°C) causes lipid peroxidation, thus generating potentially harmful compounds that may impair vascular function. This randomized, single-blind, crossover study investigated the acute effects of a high-fat meal containing either repeatedly heated (at 180°C, over 10 days, with 5 potato fries per day) sunflower oil-palm olein blend, compared with an unheated blend (containing 23.8% and 7.2% polar compounds respectively), on postprandial lipids and vascular function in 19 healthy male participants. Participants consumed each test meal on separate days, with measurements of flow-mediated dilation (FMD; primary outcome), arterial stiffness, plasma triacylglycerol (TAG), non-esterified fatty acid (NEFA), and glucose concentrations over 4 h. Postprandial vascular (FMD and arterial stiffness) responses as well as NEFA and glucose concentrations were comparable between meals. The postprandial TAG increase was lower after heated versus unheated oil (p < 0.001). These findings indicate that repeated heating of oil modifies postprandial lipaemia without acutely impairing vascular function. However, these short-term results do not address the potential cumulative effects of chronic, long-term consumption.