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Fish oil showdown: anti-inflammatory effects of EPA vs. DHA

Chronic inflammation is a driver of many health conditions, and plays a key role in heart disease. Fish oil is a popular supplement partly due to its potential anti-inflammatory actions. But which omega-3 has a greater impact, EPA or DHA?

Study under review: Randomized, crossover, head-tohead comparison of EPA and DHA supplementation to reduce inflammation markers in men and women: The Comparing EPA to DHA Study


Chronic inflammation has been identified[1] as a potential link between obesity and cardiovascular diseases. In people who have obesity, fat cells release greater amounts of inflammatory and signaling molecules (adipokines) that induce insulin resistance, blood vessel dysfunction, and systemic inflammation, all of which increase the likelihood that an artery may become damaged. Once damaged, the artery will express proteins that attract white blood (immune) cells to the location to help with repair and recovery. These immune cells also begin secreting chemicals (cytokines) that signal more immune cells to come to their location.

At this point, the damage should resolve and everything would be fantastic, if that actually happened. However, the chronic inflammation and dyslipidemia associated with obesity continually damages the arteries, never allowing them to fully repair. Accordingly, immune cells (macrophages, especially) continue to accumulate. While all this is going on, LDL particles float through the blood trying to do their job. If a lot of LDL particles are present, then there is an increased chance that some of them become trapped in the damaged artery and become oxidized. If that happens, the macrophages will eat them, thinking they’re doing the body a favor. This engulfment occurs over and over again until the macrophage is filled with lipids and becomes a “foam” cell. Foam cells cannot function properly and ultimately accumulate to form part of the plaque seen in atherosclerosis.

There is a growing body of literature suggesting that the omega-3 fatty acids EPA and DHA have the potential to reduce the inflammatory state associated with obesity. EPA and DHA serve as the precursor molecules from which anti-inflammatory compounds (resolvins, protectins and maresins) are synthesized. A recent meta-analysis[2] of 68 randomized controlled trials (RCTs) and 4601 individuals showed that EPA and DHA supplementation significantly reduced several inflammatory molecules: tumor necrosis factor alpha (TNFα), C-reactive protein (CRP, described further in Figure 1), and interleukin-6 (IL-6).

Figure 1: C-Reactive Protein: what is it good for?

Source: Ridker et al. Circulation. 1998 May.

However, this meta-analysis also revealed notable research gaps. For instance, nearly all the included studies used either a combination of EPA and DHA or used only one of the fatty acids in isolation. It therefore remains unknown whether EPA and DHA have similar or different effects on inflammatory markers. The current study was designed specifically to fill this knowledge gap and determine how EPA and DHA compare when it comes to reducing inflammation.
Obesity is associated with chronic inflammation that plays an important role in cardiovascular diseases. Current evidence suggests that EPA and DHA supplementation is an effective option for reducing inflammation, but whether one is more effective than the other remains unknown. The current study was designed to pit EPA against DHA and find out whether one could be considered more anti-inflammatory than the other.

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