The effect of olive oil supplementation on human platelet function, serum cholesterol-related variables and plasma fibrinogen concentrations: A pilot study

Seven healthy volunteers ingested 21 g olive oil daily for 8 weeks. Platelet aggregation (in platelet rich plasma and in whole blood) and thromboxane A₂ release (in platelet rich plasma) were reduced after supplementation; some of these values achieved statistical significance. There were no significant changes in platelet count and median platelet volume or in the concentrations of plasma fibrinogen or serum cholesterol, low density lipoprotein and high density lipoprotein after supplementation. Platelet membrane oleic acid content increased significantly (P<0.01), whereas arachidonic acid content decreased significantly (P<0.05). There was a significant negative correlation between the content of these two fatty acids, whether all values were considered together or whether values after 4 and 8 weeks were considered separately. This correlation suggests the possibility that an excess of oleic acid impairs the incorporation of arachidonic acid into platelet phospholipids. This phenomenon could account for the observed inhibition of platelet aggregation and reduced thromboxane A₂ release, since arachidonic acid is the substrate for thromboxane A₂. It is of interest that populations consuming large amounts of olive oil have a low incidence of ischaemic heart disease. Olive oil should no longer be considered an inactive placebo in studies assessing platelet function.