Americans spend billions on fish oil every year, mostly to protect their hearts. But the largest scientific reviews of omega-3 supplements keep pointing at the same awkward finding.
Eating fish is linked to a healthier heart. Swallowing fish oil is not clearly the same thing.
That is the message from the National Institutes of Health's National Center for Complementary and Integrative Health, which reviewed the evidence for over-the-counter omega-3 supplements.
For people who already have heart disease or very high triglycerides, the pills may help a little.
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For the general public, the picture is much thinner. Fish oil is also one of the most widely used supplements in the country.
What the biggest review found
The reference in the field is a 2020 Cochrane review that pooled 86 trials involving 162,796 people. It examined the effect of higher EPA and DHA, the two main marine omega-3 fatty acids, on heart and circulatory disease.
Higher omega-3 intake had little or no effect on deaths or cardiovascular events overall, with high-certainty evidence.
It probably made little or no difference to cardiovascular death, stroke or heart-rhythm problems. The reviewers found only a small reduction in coronary heart disease events and coronary death.
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Strongest evidence
The one heart-related effect that keeps holding up is on triglycerides, a type of fat measured in the blood.
NCCIH cites a 2020 review finding that EPA and DHA reduce triglycerides by about 15 percent.
That effect is why the Food and Drug Administration has approved prescription-strength omega-3 medications for adults with very high triglycerides, generally 500 mg/dL or higher.
Products such as icosapent ethyl (Vascepa) and omega-3-acid ethyl esters (Lovaza) are concentrated, purified doses far larger than a typical fish oil capsule, and they are prescribed alongside diet changes.
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Vascepa also carries an added FDA-approved use when taken with a statin, to lower cardiovascular risk in certain high-risk adults. Regular over-the-counter fish oil is not approved for either purpose.
Fish beats pills for the general public
For adults without diagnosed heart disease, the evidence still tips toward food. NCCIH points readers back to federal dietary guidance, which recommends adults eat at least 8 ounces of seafood a week, roughly two servings of fish such as salmon, mackerel, herring, sardines or trout.
Diets that include fish twice a week are linked to lower heart-disease risk over time.
Stroke prevention
The stroke evidence for supplements is the softest of all.
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NCCIH cites a 2020 review of 31 studies finding that increasing omega-3 supplements had little or no effect on stroke risk.
Seafood consumption itself was linked to a moderate reduction in stroke risk, an effect the pills did not reliably reproduce.
Who might actually benefit
The people most likely to gain something from an omega-3 product, according to NCCIH, are those with very high triglycerides and those with existing coronary heart disease, in both cases under a doctor's care.
For everyone else, the added value over eating fish is not well established.
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Side effects of standard fish oil are usually mild and include a fishy aftertaste, bad breath, headache and gastrointestinal symptoms.
Omega-3 supplements can also interact with blood-thinning medications, which is a reason to check with a doctor or pharmacist before starting them.
The dose most commonly studied for heart benefit is about 1 gram of combined EPA and DHA per day. That figure comes from the trials NCCIH cites, not from a general public health recommendation.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.