About the differences between (and similarites in) EPA and DHA:
Quote:
"The only way to control cellular inflammation in the brain is to maintain high levels of EPA in the blood. This is why all the work on depression, ADHD, brain trauma, etc. have demonstrated EPA to be superior to DHA
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if you use high-dose DHA it is essential to add back trace amounts of GLA to maintain sufficient levels of DGLA to continue to produce anti-inflammatory eicosanoids.
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the increased spatial territory swept out by DHA is good news for making certain areas of membranes more fluid or lipoprotein particles larger
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both are equally effective in reducing triglyceride levels
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equal activation of the anti-inflammatory gene transcription factor PPAR-gamma
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Both seem to be equally effective in making powerful anti-inflammatory eicosanoids known as resolvins
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DHA can increase the size of LDL particle to a greater extent than can EPA
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Summary
EPA and DHA do different things, so you need them both, especially for the brain. If your goal is reducing cellular inflammation, then you probably need more EPA than DHA. How much more? Probably twice the levels, nonetheless you always cover your bets with omega-3 fatty acids by using both EPA and DHA at the same time."
Source
http://www.psychologytoday.com/blog...-are-the-real-differences-between-epa-and-dha
Quote:
"When addressing specific ailments or conditions related to inflammation, however, the ratio of EPA to DHA becomes very important and can determine the efficacy of any outcome, as their physiological actions are quite distinct.
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it is suggested by a number of researchers that due to similarities in structure, EPA and DHA compete 1:1 for binding sites and that the DHA within a treatment regime appears to ‘block’ the therapeutic actions of EPA (Martins 2009; Bloch & Qawasmi et al, 2011; Sublette et al, 2011). In contrast, using pure ethyl-EPA has routinely been shown to increases the efficacy of a treatment regime and it is increasingly recognised that the absence [1] of DHA, and therefore absence of competition between EPA and DHA for biological sites of action, is responsible for the outcomes seen in such trials. Therefore oils containing DHA may not be suitable for the treatment of a variety of conditions and may explain the lack of efficacy with use of generic fish oils. "
Source:
http://igennus.com/fat-facts/epadha-ratio/