Flow-mediated dilatation is impaired by a high-saturated fat diet but not by a high-carbohydrate diet

Objective - It is unknown whether a low-fat diet, which may elevate triglycerides and lower high-density lipoprotein (HDL) cholesterol, harms the endothelium. Our aim was to determine whether a low-fat, high-carbohydrate ( CARB) diet impaired endothelial vasodilation compared with high saturated fat (SFA), monounsaturated fat (MUFA), or polyunsaturated fat (PUFA) diets. Methods and Results - Forty healthy subjects were randomly crossed over to 4, 3-week isocaloric diets high in PUFA, MUFA, or SFA, containing at least 25 g of the relevant fat or a low-fat, CARB, high - glycemic load diet. Flow-mediated dilatation (FMD), fasting blood lipids, high sensitivity C-reactive protein, plasma intercellular, and vascular adhesion molecules plasma E-and P-selectin were measured after each intervention. SFA impaired FMD compared with all other diets (5.41 +/- 2.45% versus 10.80 +/- 3.69%; P = 0.01). FMD did not change on CARB relative to MUFA or PUFA, despite 23% to 39% rises in triglyceride and 10% to 15% falls in HDL cholesterol. P-selectin was highest after SFA ( 121 +/- 52.7 ng/mL) versus MUFA ( 98 +/- 44.5 ng/mL; P = 0.001) and PUFA ( 96 +/- 36.4 ng/mL; P = 0.001). Conclusion - High SFA caused deterioration in FMD compared with high PUFA, MUFA, or CARB diets. Inflammatory responses may also be increased on this diet.