Experts warn fish oil may not be the heart-healthy miracle it’s sold as — and could even cause harm.

Once hailed as a wonder supplement for everything from heart health to sharper brains and clearer skin, fish oil is now facing a wave of scrutiny. Despite its popularity — and a booming $3.1 billion global market — experts are urging caution over what many believe is a miracle in capsule form.

“People perceive fish oil to be a wonder supplement,” says Amelia Sherry, clinical nutrition coordinator at Mount Sinai hospital. That perception, however, is increasingly at odds with the data.

Fish oil supplements are rich in omega-3 fatty acids, particularly EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), found in fatty fish like salmon, mackerel, and sardines. These omega-3s are essential, meaning our bodies can’t produce them, and they are known to support cardiovascular health, cognitive function, and the immune system.

But while eating fish is well-supported by science, the same can’t always be said for fish oil in pill form.

A 2018 meta-analysis concluded that fish oil supplements “do not benefit heart health or reduce our risk of stroke or death by any cause.” Even more troubling, a recent study found fish oil could increase the risk of heart problems and stroke in those without existing cardiovascular disease. Compounding concerns is the quality of the product — many supplements on shelves are reportedly rancid by the time they reach consumers.

“The fish oil industry is largely unregulated in the US,” warns Dr Stephen Kopecky, a cardiologist at the Mayo Clinic. “Companies can change their labels week to week.” While UK regulations are stricter, inconsistencies in EPA and DHA content remain common.

Part of the modern fish oil frenzy can be traced back to a 1985 New England Journal of Medicine paper which found coronary heart disease mortality was over 50% lower among those who ate at least 30g of fish daily. But experts say it’s a leap to attribute these outcomes solely to omega-3s. “It’s not just the fish,” says Dr Steven Nissen of the Cleveland Clinic. “It’s the lifestyle, the diet, the context.”

Indeed, populations that consume more fish often eat less processed meat and tend to make healthier choices overall. In supplement form, those nuances are stripped away.

Still, there are some situations where fish oil may help. Sherry points to evidence that fish oil can be beneficial for individuals with high triglycerides or existing heart disease. In such cases, prescription-strength fish oil — which is regulated and closely monitored — may offer value. But for the average healthy person? The benefits are far murkier.

There are also risks. One large trial involving over 13,000 patients was halted in 2020 after researchers found an increased incidence of atrial fibrillation — a dangerous irregular heartbeat — among those taking high doses of fish oil.

And then there are the more mundane downsides: burping, heartburn, and that infamous fishy aftertaste.

“The main side effect is they can burp a fishy taste,” says Kopecky, dryly.

So how should people get their omega-3s? The answer is refreshingly simple: eat real fish.

“Replacing meats high in saturated fat with fatty fish offers many more benefits than popping a supplement,” says Sherry. Kopecky adds that no supplement can compensate for a poor diet.

Fish oil supplements, he suggests, are a classic example of modern wellness culture: “We find some food that’s beneficial, isolate a compound, put it in a pill, and sell it for 10 times the cost.”

In the end, it seems the real “wonder” lies not in capsules, but in a well-balanced plate.