Similar Effects of Diets Rich in Stearic Acid or trans-Fatty Acids on Platelet Function and Endothelial Prostacyclin Production in Humans

From the Department of Applied Chemistry and Microbiology (Nutrition), University of Helsinki, Helsinki, Finland (A.M.T., M.M.); the Institut für Prophylaxe und Epidemiologie der Kreislaufkrankheiten, Munich, Germany (J.W., R.L.); and the Department of Nutrition, National Public Health Institute, Helsinki, Finland (A.A.).

Abstract—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 F₁. In vitro production of thromboxane B₂ by platelets as well as urinary excretion of ß-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.

Key Words: stearic acid • trans-fatty acids • platelet activation • 2,3-dinor-TXB₂ • 2,3-dinor-6-keto-PGF₁