BACKGROUND: Enhanced and prolonged postprandial triglyceride responses involve increased cardiovascular disease risk in type 2 diabetes. Dietary fat and carbohydrates profoundly influence postprandial hypertriglyceridemia, whereas little information exists on the effect of proteins. OBJECTIVE: The objective was to compare the effects of the proteins casein, whey, cod, and gluten on postprandial lipid and incretin responses to a high-fat meal in persons with type 2 diabetes. DESIGN: A crossover study was conducted in 12 patients with type 2 diabetes. Blood samples were collected over 8 h after ingestion of a test meal containing 100 g butter and 45 g carbohydrate in combination with 45 g casein (Cas-meal), whey (Whe-meal), cod (Cod-meal), or gluten (Glu-meal). We measured plasma concentrations of triglycerides, retinyl palmitate (RP), free fatty acids, insulin, glucose, glucagon, glucagon-like peptide 1, and glucose-dependent insulinotropic peptide. RESULTS: The incremental area under the curve for triglyceride was significantly lower after the Whe-meal than after the other meals. The RP response was lower after the Whe-meal than after the Cas-meal and Cod-meal in the chylomicron-rich fraction and higher after the Whe-meal than after Cod- and Glu-meals in the chylomicron-poor fraction. Free fatty acids were most pronouncedly suppressed after the Whe-meal. The glucose response was lower after the Whe-meal than after the other meals, whereas no significant differences were found in insulin, glucagon, glucagon-like peptide 1, and glucose-dependent insulinotropic peptide responses. CONCLUSION: The data suggest that as a supplement to a fat-rich meal in patients with type 2 diabetes, whey protein seems to outperform other proteins in terms of postprandial lipemia improvement, possibly because of the formation of fewer chylomicrons or increased clearance of chylomicrons. The trial was registered at ClinicalTrials.gov as NCT00817973.