Dietary fat and carbohydrate quality have independent effects on postprandial glucose and lipid responses

The magnitude of postprandial lipemia is influenced not only by the amount but also the type of fat and carbohydrate consumed. The aim of this study was to evaluate differences in postprandial glucose and lipid responses after a mixed meal containing low- or high-glycemic-index (GI) carbohydrate and three different types of fat varying in the degree of saturation in healthy subjects.

A randomized, controlled, single-blinded crossover study was conducted in 20 healthy Chinese men. Subjects consumed in random order six experimental isocaloric meals that differed in carbohydrate and fat quality, and contained 40 g of either saturated fat (SFA, butter), monounsaturated fat (MUFA, olive oil) or polyunsaturated fat (PUFA, grapeseed oil), and 50 g of either low-GI (basmati rice) or high-GI (jasmine rice) carbohydrate. Glucose, insulin, c-peptide, triglycerides (TG) and non-esterified fatty acids (NEFA) were measured over 4 h.

For all substrates evaluated, there were no significant interactions between fat and carbohydrate. The incremental area under the curve (iAUC) for TG was significantly lower after the SFA and PUFA meals compared with the MUFA meal, irrespective of GI. No significant difference was found for NEFA iAUC in all treatments. Glucose, insulin and c-peptide iAUCs were significantly lower after ingestion of low-GI than high-GI meals, independent of the type of fat.

A carbohydrate-rich meal (of either low or high GI) that contains butter or grapeseed oil results in lower postprandial TG concentrations relative to olive oil in healthy Chinese males. Glucose, insulin and c-peptide responses, however, are directly dependent on the GI of the meal and not on the degree of saturation of dietary fat. The trial was registered at clinicaltrials.gov as NCT02585427.