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Anti-inflammatory effects, CV benefits of fish oil in humans questioned
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Researchers were unable to detect a consistent signal indicating specialized pro-resolving mediators formed in human urine or plasma as a response to fish oil consumption, raising questions as to whether fish oils have anti-inflammatory effects which could benefit heart health in humans.
“Despite the clear shift from [omega-6] to [omega-3] epoxyeicosatrienoic acids and isoprostanes, we failed to detect a consistent signal in most cases of [specialized pro-resolving mediator] formation in urine or plasma in response to fish oil and in all cases in response to lipopolysaccharide on a background of fish oil,” Carsten Skarke, MD, the McNeil Fellow in Translational Medicine at the Institute for Translational Medicine and Therapeutics at the Perelman School of Medicine at the University of Pennsylvania, and colleagues wrote in the Journal of Lipid Research.
Carsten Skarke
According to the study background, fish oil specialized pro-resolving mediators (SPMs) have been linked with inflammation reduction in vitro and in animal models, but it was unknown whether they are formed in sufficient amounts to reduce inflammation in vivo.
Skarke and colleagues administered a high dose (17.6 g/day) of fish oil (Lovaza, Reliant/GlaxoSmithKline) for a mean of 24.2 days to 12 healthy volunteers. They also took plasma samples from a subset of six healthy volunteers who received lower doses of fish oil consistent with doses commonly taken by humans.
The outcome of interest was SPM formation in urine or plasma. In those with plasma samples, the researchers also investigated whether SPM formation occurred during and after an acute inflammatory response.
The researchers detected no consistent signal of SPM formation in urine or plasma, but “also found no alternation in the formation of SPMs during the resolution of inflammation,” Skarke told Cardiology Today. “By contrast, we readily could demonstrate formation of a series of established enzymatic and nonenzymatic oxidation products formed from omega-3 polyunsaturated fatty acids in vivo. On this basis, we conclude that our study fails to provide evidence consistent with the hypothesis that SPMs mediate an anti-inflammatory action of fish oil.”
The implication, he said, is that “these findings prompt reconsideration of the fundamental question: How strong is the evidence that fish oils confer a [CV] benefit? … We find no evidence supportive of a mechanism based on SPMs but we doubt the purported benefits themselves, based on evidence.”
Including fish in one’s diet is a better idea for enhancing CV health than taking fish oil supplements, according to Skarke. He noted that “there is a place for fish oils in certain forms of triglyceridemias, but after that, their efficacy is not proven.” – by Erik Swain
For more information:
Carsten Skarke, MD can be reached at Institute for Translational Medicine and Therapeutics (ITMAT), 8036 Maloney Building, 3600 Spruce St., Philadelphia, PA 19104; email: cskarke@mail.med.upenn.edu.
Disclosure: Skarke and the other researchers report no relevant financial disclosures.
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