Dr. Anil Nigam at the ÉPIC Center of the Montreal Heart Institute conducted a study to determine if the type of fat in a meal impacted the ability of arteries to dilate. The findings of this study were recently presented at the Canadian Cardiovascular Congress. A reduction in the ability of arteries to dilate is an established method of assessing endothelial health.Mediterranean-style meal vs. fast food mealDr. Nigam compared the effects of consuming a either a typical Mediterranean-style meal or a fast food meal on the vascular endothelium. By measuring endothelial function, it is possible to determine how easily the arteries will dilate after a temporary, five-minute occlusion, following the consumption of the two types of meals. This is a very telling analysis for researchers to perform, since endothelial function is closely linked to the long-term risk of developing coronary artery disease.The subjects consumed either the Mediterranean-style meal or the saturated fat-rich fast food meals one week apart and each after a 12-hour overnight fast. The Mediterranean-style meal was composed of salmon, almonds, and vegetables cooked in olive oil with 51% of total calories coming from fat. The second meal consisted of a sandwich (made of a sausage, an egg, and a slice of cheese) and three hash browns. This meal contained 58% fat calories and was extremely rich in saturated fatty acids and cholesterol. At two hours and four hours after each meal, participants underwent further ultrasounds to assess how the food had impacted their endothelial function. Dr. Nigam and his team found that after eating the fast food meal, his subject's arteries dilated 24% less than they did when in the fasting state. In contrast, the arteries were found to dilate normally and maintain good blood flow after the Mediterranean-type meal.The study revealed that participants with higher blood triglyceride (TG) levels seemed to benefit more from the healthful meals than those whose fasting TG levels were lower. The adverse response of the arteries of men with elevated TG levels to the fast food meal was greater than it was for the men whose TG levels were lower. “We believe that a Mediterranean-type diet may be particularly beneficial for individuals with high triglyceride levels, such as patients with metabolic syndrome, precisely because it could help keep arteries healthy,” Dr. Nigam said.The results of this recent study are consistent with earlier studies. A study of type 2 diabetes mellitus subjects found that endothelial function was impaired a few hours after a saturated fat and cholesterol-rich butter containing meal but not when polyphenol-rich olive oil replaced the butterfat. [Tentolouris N, et al. Differential effects of two isoenergetic meals rich in saturated fat or monounsaturated fat on endothelial function in subjects with type 2 diabetes. Diabetes Care 2008;31:2276-8]. Another study looked at the impact of a meal containing either safflower oil or coconut oil on FMD dilation and on the anti-inflammatory impact of high-density lipoprotein (HDL) particles. They found that the saturated fat-rich meal reduced the anti-inflammatory action of HDLs and impaired endothelial function as measured by FMD. The polyunsaturated fat rich meal by contrast did not impair the anti-inflammatory properties of HDLs nor did they cause a reduction in FMD. [Nichols SJ, et al. Consumption of saturated fat impairs the anti-inflammatroy properties of high-density lipoproteins and endothelial function. Am J Cardiol 2006;48:715-20].Yet another study compared the impact of consuming either a low-fat meal or a high-fat meal containing mostly unsaturated fats that been used for cooking in a fast food restaurant or the same the same oil before used for frying on endothelial function. Neither the unused oil nor the low-fat diet impaired endothelial function but there was a marked reduction in FMD several hours after the same vegetable oil had been used in a fast food restaurant for frying. [Williams MJA, et al. Impaired endothelial function following a meal rich in used cooking fat. J Am Coll Cardiol 1999;33:1050-5].Bottom Line: Each meal rich in saturated fat and cholesterol appears to alter blood lipids and promote inflammation that impair endothelial function in ways associated with increased cardiovascular disease risk. While oils rich in unsaturated fatty acid do not appear to adversely impact arterial health, this may not be so if the oils are used repeatedly for frying.by James J. Kenney, PhD, FACN