Here's a small study that found a meal rich in coconut oil, where the fat is primarily saturated (compared to a meal high in safflower oil where the fat is primarily unsaturated) impaired the anti-inflammatory action of HDL, and resulted in impaired blood vessel function for several hours after the meal:
Consumption of Saturated Fat Impairs the Anti-Inflammatory Properties of High-Density Lipoproteins and endothelial Function, Journal of the American College of Cardiology, 2006
The aim of the study was:
"... to define the effect of consuming a single high-fat meal, differing in fatty acid composition, on the ability of high-density lipoproteins (HDLs) to inhibit the expression of proinflammatory adhesion molecules by endothelial cells and on large and small vessel function."The meal:
"Subjects consumed 1 of 2 isocaloric meals comprising a slice of carrot cake and a milkshake containing 1 g of fat/kg of body weight. The first meal contained safflower oil. The second meal contained coconut oil."Findings: The coconut oil meal reduced the anti-inflammatory properties of HDL, while the polyunsaturated fat meal actually enhanced those properties. (HDL was found to inhibit release of adhesion molecules from endothelium - from the lining of blood vessels. That's good. The presence of adhesion molecules (ICAM-1 and VCAM-1) can promote atherosclerosis.)
"Consumption of a saturated fat reduces the anti-inflammatory potential of HDL and impairs arterial endothelial function. In contrast, the anti-inflammatory activity of HDL improves after consumption of polyunsaturated fat. These findings highlight novel mechanisms by which different dietary fatty acids may influence key atherogenic processes."Also, forearm blood flow increased more after the polyunsaturated than saturated fat (coconut oil) meal.
"Post-hyperemic forearm blood [microvascular] flow significantly increased 3 h after consumption of the polyunsaturated fat by 45 +/-14% and by 21 +/- 11% after the saturated fat meal."The authors suspect it may be the result of fatty acid changes in the phospholipid layer (cell membrane) of the HDL after a meal.
"The present study raises the possibility that the differential effects of dietary fats on the antiinflammatory potential of HDL and endothelial function may contribute to the apparent benefits of polyunsaturated over saturated diets observed in the epidemiologic literature."