Written by Alan Aragon regarding high EPA/DHA intake:
The Dark Side of Over-doing Fish Oil Supplementation
Yes, Luke, there is always a dark side. In the world of unchecked marketing hype, fish oil has definitely gotten the “more is better” stamp. The problem is, EPA and DHA have a well-documented ability to suppress the body’s immune response. Although not as consistent as the immune effects, data also exist on the ability of EPA and DHA to increase bleeding time and oxidation. Let’s take a look at a couple of the published peer-reviewed research that no one in the fitness industry talks about.
Thies and colleagues examined the 12-week effect of various fatty acid supplement mixes on healthy subjects [19]. Various blends of placebo oil and oils rich in ALA, GLA, AA, DHA, or EPA (720mg) + DHA (280mg) were compared. Total fat intake from the 9-capsule dose was 4 g/d. The EPA/DHA treatment was the only one that had a negative effect on immunity, significantly decreasing natural killer cell activity by 48%. This effect was reversed after 4 weeks of ceasing intake of the supplement.
Rees and colleagues investigated the effects of various amounts of EPA on immune markers in young and older men [20]. In a 12-week study, EPA was incorporated into plasma and mononuclear cell phospholipids. Supplemental EPA in amounts of 1.35, 2.7, and 4.05g/day caused a dose-dependent decrease in neutrophil respiratory burst, indicating the suppression of a cellular defense against immunity threats. This effect was seen in the older, but not the younger men. Based on these and the previous data, if you’re not a spring chicken, and immunity is an issue, you might not want to go hog-wild on the fish oil dosing.