Fish Oil’s Slippery Health Claims

Fish Oil
Illustration by Newsweek; Source photos: Neville Mountford-Hoare / Photo Alto; Dorling Kindersley / Getty Images

For the past 10 years, I’ve started my morning with a handful of fish-oil gel caps. Like many, I hoped this simple step would help prevent the most common diseases of modernity—heart attacks and strokes. So my day was darkened by a recent article in the Journal of the American Medical Association that reviewed the fish-oil evidence and found no demonstrable benefit.

My reasoning had been relatively sound. The fish story started in the 1970s, when small observations about fish-based diets suggested that eating more fish meant a longer life. With this lead, clinical trials were organized and patients enrolled. The problem of normalizing fish consumption was solved by a process called wet pressing, whereby large amounts of fish are cooked, pressed, and centrifuged to remove the oil, which is put into a soft gel capsule. Most of the studies have relied on this product rather than on counting pieces of actual salmon eaten. The science hinged on the observation that omega-3 fatty acids have a calming effect on platelets, those sticky components of blood that can block the circulation.

In the popular imagination, fish oil swiftly took its place as a cure-all, like its quasi-antecedent, cod-liver oil. True believers claim omega-3s can not only reduce heart attacks and strokes but also prevent cancer, sharpen memory—even ameliorate attention-deficit problems. Yet even as enthusiasm grew, additional studies yielded ambivalent results. To settle the matter, in stepped a group of researchers who conducted a meta-analysis on what they deemed the 20 most rigorous reports. These studies looked at the cardiovascular fate of 68,680 people—half on fish oil—and found no reduction in death, heart attacks, or strokes. None. And it wasn’t even close.

So does that mean it’s time to toss the fish-oil capsules from the medicine cabinet? Not yet. The new meta-analysis, though strong in its agnosticism, is still only a meta-analysis—a study of several studies. And among some experts, any meta-analysis is a sketchy enterprise. For these purists, the meta-analysis that purports to derive a large simple truth by throwing together small messy studies actually does little more than make an even bigger mess of the entire business.

I myself will continue to choke down the gel caps until additional analysis is done. I’m not the only diehard. Last year Americans spent $1.1 billion on fish-oil supplements, according to the Nutrition Business Journal. Already the fish-oil tycoons have dispatched their talking heads to point out, loudly, the limits of the study. But this does seem to signal the end of yet another shortcut to better health—perhaps we’ll have to go back to the tedium of the healthy diet, including eating real fish.

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