Marine oils dose-dependently inhibit vasoconstriction of forearm resistance vessels in humans

The effects of dietary supplementation with marine oils on vascular reactivity in human forearm resistance arteries were studied. Healthy male adults (six to nine subjects per group) were given either maxEPA capsules (content: eicosapentaenoic acid, 0.178 g/g; docosahexaenoic acid, 0.116 g/g) at doses of 20, 10, or 5 g/day or placebo capsules at 20 g/day for 28 days. Capsule compliance was confirmed by measurement of platelet membrane incorporation of n-3 fatty acids. Blood pressure was not affected by either maxEPA or placebo. The influence of treatment interventions on forearm vasoconstrictive responses to local infusions of angiotensin II and norepinephrine was examined using venous occlusion plethysmography before and after treatment. Responses to both agonists were significantly suppressed by 20 g/day maxEPA (slopes before and after maxEPA, respectively: angiotensin II, 3.34 and 0.89; norepinephrine, 0.91 and 0.41). When analyzed as difference in area under the dose-response curves, the suppressive effects of maxEPA were clearly dose dependent (angiotensin II: 20 g area reduced by 72%, 10 g by 67%, 5 g by 33%). Similarly, responses to norepinephrine were dose-dependently suppressed by maxEPA (20 g area reduced by 61%, 10 g by 63%, and 5 g by 33%). Placebo had no effect on the responses to either constrictor. The responses to both agonists returned to preoil levels after 2 months' discontinuation of 20 g/day maxEPA. We conclude that the suppressive effects of marine oils on vascular reactivity may, in part, contribute to their cardioprotective influence in humans.