Similar effects of diets rich in stearic acid or trans-fatty acids on platelet function and endothelial prostacyclin production in humans.

The effects of stearic acid (C18:0) and trans-fatty acids (trans-FAs) on measures of platelet function and prostacyclin (PGI2) production are poorly understood in humans. In this controlled dietary study, platelet function and endothelial PGI2 production were studied in healthy humans after they consumed diets rich in C18:0 or trans-FAs. For 5 weeks, 80 subjects consumed a baseline diet high in saturated FAs and were then switched to a diet containing 9.3% of energy as stearic acid or a diet containing 8.7 energy% as trans-FAs from hydrogenated vegetable oils for another 5 weeks. All diets contained 32.2 to 33.9 energy% fat, 14.6 to 15.8 energy% saturated plus trans-FAs, 12.2 to 12.5 energy% cis-monounsaturated, and 2.9 to 3.5 energy% polyunsaturated FAs. No significant differences between the C18:0 and trans-FA diets were found in the urinary excretion of 2,3-dinor-thromboxane B2 or 2,3-dinor-6-keto-prostaglandin F1alpha. In vitro production of thromboxane B2 by platelets as well as urinary excretion of beta-thromboglobulin were also similar after both diets. Collagen-induced in vitro aggregation was significantly enhanced after the C18:0 diet compared with the trans-FA diet (P=.02), whereas no differences between the diets were found with ADP. The results indicate similar effects of C18:0 and trans-FA diets on platelet activation and endothelial PGI2 production.