Comparison of the effects of diets rich in stearic acid versus myristic acid and lauric acid on platelet fatty acids and excretion of thromboxane A₂ and PGI₂ metabolites in healthy young men

The present study compared the effects of diets rich in stearic acid (C18:0) versus one high in lauric and myristic acid (C12:0, C14:0) on platelet phospholipid fatty acid levels and concentrations of urinary thromboxane B₂ (TXB₂) and 6-keto-PGF_1α, which are stable metabolites of thromboxane A₂ (TXA₂) and PGI₂ and indicators of cardiovascular hemostasis. A diet high in dairy butter (B) was the source of C12:0 and C14:0; C18:0 was provided by diets high in cocoa butter (CB), milk chocolate (CHOC) or CB + B in a 4:1 ratio (MIX). A randomized, crossover double-blind experimental design was used. Experimental subjects (n = 15) consumed each diet for 26 days, with a 1-month washout period between each experimental period. Urine and blood were collected from each subject at the beginning and end of each dietary period. Urinary TXB₂ and 6-keto-PGF_1α were analyzed by radioimmunoassay (RIA). There were no effects of diet on the 24-hour excretion of either metabolite or on the ratio of 6-keto-PGF_1α TXB₂, even though there were significant changes in the eicosanoid precursor, arachidonic acid (C20:4n-6), in platelet phospholipids. C20:4n-6 levels increased (44.8% ± 1.0% to 47.1% ± 1.3%; P < .05) in the phosphatidylethanolamine phospholipid subclass in subjects on the B diet and decreased in the phosphatidylcholine subclass on the CB diet (16.5% ± 1.0% to 14.2% ± 1.1%; P < .05) compared with baseline values. Although there were modest effects of diets high in C12:0 and C14:0 versus C18:0 on the fatty acid precursor of TXA₂ in platelet phospholipids, these were not associated with any differences in urinary eicosanoid excretion. Thus, our results demonstrate that diets high in these respective fatty acids do not affect hemostasis compared with baseline values, as measured by eicosanoid excretion.