Effect of ω-3 fatty acid-containing phospholipids on blood catecholamine concentrations in healthy volunteers: a randomized, placebo-controlled, double-blind trial

Objective We previously reported that administration of fish oil rich in docosahexaenoic acid (DHA) increased the plasma ratio of epinephrine to norepinephrine (NE) at rest in young adults who were under chronic stress and that this effect was achieved mainly through depression of NE. However, not many reports have documented the effects of eicosapentaenoic acid (EPA) and DHA on blood catecholamine levels in healthy humans. Therefore, we performed another intervention study to test their effect on catecholamines with healthy subjects under no chronic stress. Methods Twenty-one healthy young adults (15 men and 6 women) were randomly assigned to an ω-3 group (n = 9) or a control group (n = 12) in a double-blind manner. Twenty capsules of shellfish-derived lipids containing 762 mg of EPA plus DHA per day were administered to the ω-3 group for 2 mo. The controls took the same amount of placebo capsules. Fasting blood samples after a 30-min rest with a catheter in a forearm vein were obtained at the start and the end of the study for catecholamine measurements. Results EPA but not DHA concentrations in red blood cells significantly increased in the ω-3 group compared with the control group (P < 0.001). Plasma NE concentrations were significantly decreased in the ω-3 group (from 1.49 ± 0.39 nmol/L to 1.05 ± 0.14 nmol/L) compared with the control group (from 1.12 ± 0.24 nmol/L to 1.39 ± 0.32 nmol/L) with analysis of covariance (P < 0.001). The differences remained significant (P = 0.01) even after deletion of three subjects in the ω-3 group who had the highest baseline NE values and one in the control group who had the lowest baseline NE value to nullify a significant baseline differences in NE between groups. Conclusion This study demonstrated that EPA plus DHA supplementation lowered plasma NE concentrations in normal volunteers even at the small dose of 762 mg of EPA plus DHA per day. This effect of EPA plus DHA to lower plasma NE concentrations may be important to understand some of the effects of fish oils on diseases.