Modification of human platelet function by a diet enriched in saturated or polyunsaturated fat.

Twelve healthy male subjects were maintained on a saturated fat (SF) dietary regimen followed by a polyunsaturated fat (PUF) regimen. At selected intervals a number of tests were carried out to assess the effect of SF or PUF on platelet composition and activation. Concomitant with the fall in serum cholesterol, associated with the PUF diet, there was a decrease in plasma heparin neutralizing activity (as measured by the heparin--thrombin clotting time), and a fall in the number of circulating platelet aggregates was also observed. These two parameters suggest diminished platelet activation. Malondialdehyde production (an index of prostaglandin synthesis) was unchanged throughout the two dietary periods. Changes in the quality of the dietary fat were manifested in the phospholipid fraction of platelet lipids, particularly phosphatidyl choline and sphingomyelin. Platelet counts of whole blood were significantly decreased when subjects were consuming PUF, but not all of these alterations were reflected in platelet-rich plasma. These results indicate that platelets may be activated in apparently normal people consuming a SF diet (the standard diet of developed countries) and that this activation may be decreased by replacement of dietary SF with PUF.