Fishy Evidence on Fish Oil


I recently wrote a letter to the editor to JAMA Internal Medicine on the article posted above. The editors rejected it, but I’ve posted it here for your viewing pleasure.

Dr. Curfman recently highlighted the lack of benefit of ω-3 fatty acids in recent studies, despite their initial promise, in the secondary prevention of cardiovascular disease. His editorial also mentions the American Heart Association’s recommendation that adults consume fish at least twice weekly and himself concludes with similar advice for his readers.

The consumption of fish on a regular basis was brought to the forefront because of the ω-3 fatty acids within fish oil and their presumed beneficial properties on cardiovascular health, as Dr. Curfman mentioned. However, subsequent studies, including large meta-analyses using endpoints like all-cause mortality and primary prevention of cardiovascular disease, have failed to show any benefit of ω-3 fatty acids. Additionally, one of the original studies, the DART-2 trial, even showed a statistically significant increase in sudden cardiac death with increased fish oil consumption.

The continued consumption of fish is all the more concerning given the elevated concentrations in fish of toxic substances like polychlorinated biphenyls (PCBs), mercury, lead, cadmium, and dioxins, all of which can adversely affect human health. Additionally, a meta-analysis of fish consumption has shown that a single serving of fish in the U.S. per week has been associated with an increase in the risk of diabetes, possibly from the PCBs or mercury, or both. Further, both childhood and current consumption of fish has been shown to decrease cognitive performance in older Americans, who are most likely to suffer from cardiovascular disease. Until we have strong, compelling evidence on the health benefits of fish or fish oil, it may be safer to avoid its consumption entirely or obtain fatty acids from sources with lower concentrations of pollutants, like algae.


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