Different effects of eicosapentaenoic acid and olive oil on blood pressure, intracellular free platelet calcium, and plasma lipids in patients with essential hypertension
In a randomized, double-blind, crossover study our specific aim was to examine the effects of a dietary fish oil or olive oil supplementation on blood pressure, intracellular free platelet calcium, plasma lipoproteins, and circulating vasoactive substances such as norepinephrine, epinephrine, and renin in patients with essential hypertension. Ten hypertensive patients (WHO classes I, II) were randomly assigned to receive 9 g fish oil or 9 g olive oil daily for 6 weeks after a 4-week baseline period. The 6-week treatment periods were separated by a 4-week wash-out. During treatment with fish oil diastolic blood pressure decreased from 103±1 to 98±2 mmHg (P<0.05) but did not change significantly during olive oil intake. Systolic blood pressure was not affected by either treatment. Intracellular free platelet calcium decreased in patients receiving fish oil (from 102±8 nM to 86±6 nM, P < 0.05) but was not significantly altered by olive oil treatment. In contrast, the dose-response curve for thrombin-induced intracellular free platelet calcium was not altered by the fish oil enriched diet. Plasma triglycerides decreased by approximately 40% in the fish oil group while low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and total cholesterol were not altered. Renin activity, norepinphrine, and epinephrine in plasma were not influenced by fish oil supplementation. We conclude that a moderate increase in dietary fish oil reduces diastolic blood pressure, intracellular free platelet calcium, and plasma triglycerides in patients with essential hypertension. The decrease in basal intracellular free platelet calcium concentration does not seem to be due to a diminished responsiveness of the calcium messenger system to thrombin.