Fish oil is one of the most-sold supplements in the world. Here is what omega-3 fatty acids actually do, how to read a label properly, and where the evidence is strong versus shaky.
EPA and DHA — the parts that matter
The two omega-3s with the most research behind them are EPA and DHA, both found in oily fish. A plant form, ALA (from flax and walnuts), converts to EPA and DHA only inefficiently in the body. The NIH Office of Dietary Supplements publishes a plain-language sheet on omega-3 fatty acids.
How to read the label (this is where people get caught)
A bottle shouting “1,000 mg fish oil” is telling you the weight of the oil, not the dose that matters. Turn it over and add up EPA + DHA per serving — that number is often only 300 mg. Common supplemental intakes fall around 1–2 g of combined EPA+DHA daily.
What the research supports
Evidence is reasonably good for triglyceride lowering at higher doses, and moderate for joint comfort and stiffness. Claims about memory, mood and general disease prevention are much less settled. Eating fish twice a week is the baseline most guidelines still recommend; supplements are a fallback when that is not realistic.
Omega-3 Fish Oil (e.g. Nordic Naturals, NOW)
- Add up EPA + DHA per serving — 1–2 g daily is a common range
- Third-party testing (IFOS, USP or NSF) helps with purity and freshness
- Algae-based versions are available for vegans
Widely available
Check Price →Freshness, burps and safety
Rancid fish oil is common and unpleasant — if a capsule smells strongly off, do not push through it. Keeping the bottle in the fridge helps, as does taking it with food. High doses can thin the blood slightly, so talk to your healthcare provider if you take anticoagulants or are heading for surgery.
Comparing joint options? See our guide to the best joint supplements.