Conclusion
Research on fish oil (omega-3 fatty acids, EPA and DHA) and the heart is mixed. Some meta-analyses report a small reduction in heart attack and death from coronary heart disease, while large trials of low-dose supplements in the general population show little clear benefit.
The benefit of eating fish as part of a diet and the benefit of taking high-dose supplements are worth considering separately.
How much does it help?
A meta-analysis pooling 13 randomized trials and about 127,000 people found small reductions in heart attack, death from coronary heart disease, and cardiovascular death, with larger effects at higher doses. No benefit was seen for stroke.
In low-dose primary-prevention trials in the general population, however, the added benefit was small. High-dose prescription trials are split: one high-purity EPA trial helped higher-risk patients, while another high-dose trial showed no benefit.
What the research shows
The evidence base includes many randomized trials and meta-analyses. Observational studies, which suggest that people who eat more fish have less heart disease, do not always agree with randomized trials. Effects vary with a person's cardiovascular risk and with dose, tending to appear in higher-risk people and at higher doses.
Cautions
- High doses (roughly 1.8 to 4 g per day) have been linked to a higher risk of atrial fibrillation, more so at higher doses and at prescription-strength amounts
- If you take anticoagulants, watch for a tendency toward bleeding
- Old, oxidized products lose quality; pay attention to storage and freshness
- People with heart disease or high risk should consult a physician rather than raising the dose on their own
A simple analogy
If adding fish to your diet is like preparing the soil, a supplement is like extra fertilizer. The poorer the soil, the more visible the fertilizer's effect; but adding too much can create a separate problem, such as an irregular heartbeat.