How to read a fish oil label: EPA, DHA and the number that matters.
Fish oil is one of the most common supplements in the world and one of the easiest to misread. The front of the bottle tells you how much oil is in a capsule. What matters is on the back.
Find EPA + DHA per serving
EPA and DHA are the two long-chain omega-3 fats the research is about. A typical 1,000 mg fish oil capsule holds around 300 mg of them combined; a concentrate may hold 600 mg or more. Check two more things on the same panel:
- Serving size. Some labels give the amount for two or three capsules.
- EPA and DHA separately. Products use different ratios, and no single ratio is right for everyone.
Plant omega-3 (ALA, from flax, chia and walnuts) is good food, but the body converts only a small share of it into EPA and DHA. If you eat little fish, algae oil is the vegetarian source of EPA and DHA.
Freshness
Omega-3 fats oxidize. Producers measure this with peroxide and anisidine values, combined into a TOTOX score, and the industry's voluntary standard (the GOED monograph) sets upper limits for each. A good maker will show you the result for the batch. At home, a strong fishy smell when you open the bottle or bite a capsule is a sign the oil has gone off.
Purity
Molecular distillation removes most mercury and other contaminants, which build up in large predatory fish more than in the small fish (anchovy, sardine) most oils are made from. A certificate of analysis should list heavy metals and, ideally, PCBs and dioxins.
How much
There is no US daily allowance for EPA and DHA. Many dietary guidelines suggest eating fish about twice a week, which works out at roughly 250–500 mg a day. The US FDA advises not to exceed 3 g a day of EPA and DHA combined, with no more than 2 g from supplements; the European Food Safety Authority considers up to 5 g a day safe for adults.
Take it with food
Omega-3s are absorbed better with a meal that contains fat, and taking them with food also cuts down on fishy burps.
Ask your doctor first if you
- take blood thinners or have a bleeding disorder;
- have a fish or shellfish allergy;
- have heart-rhythm problems. Some large trials of high-dose omega-3 found a small increase in atrial fibrillation.
Sources
- NIH Office of Dietary Supplements, Omega-3 Fatty Acids: Fact Sheet for Health Professionals.
- EFSA, Scientific Opinion on the Tolerable Upper Intake Level of EPA, DHA and DPA, 2012.
- Global Organization for EPA and DHA Omega-3s (GOED), Voluntary Monograph: oxidation and contaminant limits.
This guide is general information, not medical advice. Talk to your doctor or pharmacist before starting a supplement if you are pregnant or nursing, take medication, or have a medical condition.