The cardiometabolic health effects of repeatedly heated culinary seed oils are uncertain. The process of heating oils high in polyunsaturated fatty acids causes lipid peroxidation and can generate potentially harmful compounds that may impair vascular function (1–3) . This study investigated the acute impact of a high-fat meal containing either repeatedly heated or unheated sunflower oil–palm olein blend on postprandial lipid responses and vascular function in healthy men. In a randomised, single-blind, crossover study, 19 healthy men (mean age 22.4 ± 3.7y; BMI 22.6 ± 2.3 kg/m 2 ) consumed test meals containing 50 g of either repeatedly heated or unheated oil on separate days with at least a one-week washout. Heated oil underwent commercial deep-frying conditions for 10 consecutive days. Postprandial measurements were collected at baseline, 3 h, and 4 h and included plasma triacylglycerols (TAG), non-esterified fatty acids (NEFA), glucose, vitamin E, flow-mediated dilation (FMD) and arterial stiffness indices (peripheral and central augmentation indices). Standardised low-fat meals and abstinence from exercise, alcohol, and caffeine preceded each test day. Data were analysed using repeated-measures ANOVA, with Bonferroni-adjusted post hoc tests. Ethical approval was obtained from King’s College Ethics Committee (CREC/06/07-45). Postprandial TAG responses were significantly lower following the heated oil meal compared to the unheated oil at 3 h (1.6 1.3–1.9 vs. 2.0 1.6–2.4 mmol/L, P < 0.001) and 4 h (1.8 1.5–2.1 vs. 2.3 1.8–2.7 mmol/L, P < 0.001). There were no differences in the postprandial change in NEFA or glucose between meals. Plasma vitamin E concentrations did not differ significantly between meals or time points. FMD% remained unchanged after both meals and was not different between meals. Arterial stiffness decreased postprandially, as indicated by reductions in PAIx and CAIx, but was not affected by oil type (PAIx: –17.7% –25.5, –10.0 heated; –18.5% –27.4, –9.7 unheated; CAIx: –47.4% –52.0, –42.8 heated; –46.3% –53.1, –39.4 unheated; p < 0.001 for time) Both heated and unheated oil meals elicited the expected postprandial increase in plasma TAG, although the rise was attenuated following the heated oil meal. Vascular function and arterial stiffness showed similar responses between meals. Repeatedly heating oil alters postprandial lipid responses but does not acutely impair vascular function. Further controlled trials with larger sample sizes, detailed characterisation of oil degradation products, and extended postprandial monitoring are needed to clarify the metabolic and vascular effects of repeatedly heated oils.
Brownson-Smith et al. (Fri,) studied this question.