Do omega-3 (fish oil) supplements help my heart?
For people with existing heart disease there is reasonable evidence that omega-3 supplements help, especially at high doses of pure EPA. For healthy people without heart complaints, that evidence does not currently exist.
Omega-3 supplements (EPA and DHA, such as fish oil) measurably reduce the risk of a heart attack. A meta-analysis of 40 randomised trials involving more than 135,000 people found a 13% reduction1. In concrete terms: on average, 272 people need to take the supplement to prevent one heart attack. Fatal heart attacks fell by as much as 35%, although that estimate is less certain.
However, no significant effect was found on the broader measure of all cardiovascular events combined. Omega-3 therefore does something for the heart attack itself, but does not move the overall counter.
Formulation makes a big difference. High doses of pure EPA produced a clear reduction in risk in a large trial2,3. Combination products containing both EPA and DHA, or lower doses, yielded mixed or neutral results. Not all fish oil capsules are the same: the strongest evidence applies to high-dose, pure EPA.
The American Heart Association concluded that omega-3 is worthwhile if you already have heart disease, which is called 'secondary prevention'4. At the same time, it acknowledges that not every large trial showed a benefit. For healthy people without heart complaints, a protective effect has not been demonstrated in randomised trials.
Observational research does show an association: people with lower omega-3 levels in their blood more often experienced serious cardiac events and sudden cardiac death5. But this is an association, not a proven cause. People with a healthier lifestyle eat more oily fish anyway, and therefore have higher levels.
All claims are based on one meta-analysis (PMID 32951855, 40 randomised trials, more than 135,000 participants), an advisory report from the American Heart Association (PMID 28289069), two additional studies on pure EPA versus EPA+DHA (PMID 33027227, 21933782), one systematic review on DHA (PMID 29494205), and one observational study on omega-3 levels in the blood (PMID 24566438). The meta-analysis is robust; the remaining sources are of moderate quality or observational.