Docosahexaenoic acid but not eicosapentaenoic acid lowers ambulatory bloodpressure and heart rate in humans

Animal studies suggest that the 2 major omega 3 fatty acids found in fish, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may have differ ential effects on blood pressure (BP) and heart rate (HR). The aim of this study was to determine whether there were significant differences in the ef fects of purified EPA or DHA on ambulatory BP and HR in humans. In a double -blind, placebo-controlled trial of parallel design, 59 overweight, mildly hyperlipidemic men were randomized to 4 g/d of purified EPA, DHA, or olive oil (placebo) capsules and continued their usual diets for 6 weeks. Fifty-s ix subjects completed the study. Only DHA reduced 24-hour and daytime (awak e) ambulatory BP (P<0.05), Relative to the placebo group, 24-hour BP fell 5 .8/3.3 (systolic/diastolic) mm Hg and daytime BP fell 3.5/2.0 mm Hg with DH A. DHA also significantly reduced 24-hour, daytime, and nighttime (asleep) ambulatory HRs (P=0.001). Relative to the placebo group, DHA reduced 24-hou r HR by 3.5+/-0.8 bpm, daytime HR by 3.7+/-1.2 bpm, and nighttime HR by 2.8 +/-1.2. EPA had no significant effect on ambulatory BP or HR. Supplementati on with EPA increased plasma phospholipid EPA from 1.66+/-0.07% to 9.83+/-0 .06% (P<0.0001) but did not change DHA levels. Purified DHA capsules increa sed plasma phospholipid DHA levels from 4.00+/-0.27% to 10.93+/-0.62% (P<0. 0001) and led to a small, nonsignificant increase in EPA (1.52+/-0.12% to 2 .26+/-0.16%). Purified DHA but not EPA reduced ambulatory BP and HR in mild ly hyperlipidemic men. The results of this study suggest that DHA is the pr incipal w3 fatty acid in fish and fish oils that is responsible for their B P- and HR-lowering effects in humans. These results have important implicat ions for human nutrition and the food industry.