The Truth About Fish Oil Supplements: What the Latest Research Says

Updated July 2026

Fish oil supplements are hugely popular with people hoping to protect their hearts. But do they actually work? The marine omega-3 fatty acids in those capsules, DHA and EPA, are widely believed to guard against heart disease. The real story is more complicated than the bottle would suggest.

Do fish oil supplements actually prevent heart disease?

The honest answer is that the evidence is mixed, and it comes down to who's taking them. The large VITAL trial followed nearly 26,000 middle-aged and older adults for about five years and found that 1 gram of fish oil a day did not significantly lower the overall risk of major cardiovascular events or death from heart disease across the study population as a whole. On that basis, fish oil as a blanket health strategy for everyone doesn't hold up.

But dig into the same data and some groups did appear to benefit: people who ate little fish to begin with, those with several heart disease risk factors, and African American participants, who showed the most striking reduction in heart attacks. Oddly, those same groups didn't see a benefit for stroke, which is a reminder of how uneven this picture is.

What about the prescription version?

That's a separate story. The REDUCE-IT trial tested a high-dose prescription form of EPA called icosapent ethyl, at 4 grams a day, in people already at high risk from conditions like diabetes or existing cardiovascular disease. It found a significant reduction in major cardiovascular events, which led to FDA approval of the drug (Vascepa) for select high-risk patients.

But even that result carries an asterisk. The placebo in REDUCE-IT was mineral oil, chosen to mimic the look and feel of the omega-3 capsules. Mineral oil is pro-inflammatory, so it's possible that some of the apparent "benefit" wasn't the drug lowering risk at all, but the placebo raising it. It's a genuine question, and telling that the maker isn't likely to rerun the trial against an inert placebo to settle it.

Are omega-3s from food better than a capsule?

For most people, yes. You can get all the EPA and DHA you need from food, and it may be better for your heart than a supplement. Fatty fish like salmon, mackerel, and sardines deliver those omega-3s alongside other nutrients that likely enhance the benefit, and without some of the downsides of capsules, such as concentrated heavy metals or oxidized oil. High-dose fish oil supplements also carry their own risks, including a higher chance of atrial fibrillation (an irregular heart rhythm that can raise stroke risk) and bleeding, problems generally not seen when you get your omega-3s from food.

There's one more piece most people miss. Beyond the marine omega-3s, there's a plant-based one called ALA, and it's essential, meaning your body can't make it and has to get it from food. Your body can convert ALA into EPA and DHA, but not the other way around, so eating fish alone isn't enough. You also need ALA sources like flax, chia, and walnuts, which is exactly the combination Step One Foods is built around.

So who should take a fish oil supplement?

The story is still unfolding. If you fall into a high-risk group or eat little to no fish, a supplement might offer some benefit, but it's worth discussing with your doctor rather than starting on your own. And don't overdo it: fish oil may be "natural" and "just a supplement," but every compound you put in your body has a biological effect. For most people, the safer bet is a heart-healthy diet built around omega-3-rich foods, fatty fish, flaxseed, walnuts, and chia. Supplements can fill a specific gap, but they're no replacement for real nutrition.

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