What is fish oil?
Fish oil is oil from fatty sea fish or fish liver and the classic source of the omega-3 fatty acids EPA and DHA. It is sold as a supplement in capsules or liquid form; what matters is the EPA and DHA content, freshness and purity.
What is fish oil made of?
Fish oil consists mostly of triglycerides that carry EPA and DHA. It is obtained from oily fish such as herring, sardine, mackerel, anchovy or salmon. Cod liver oil is a special case: it comes from cod liver and also contains vitamins A and D.
Fish oils come in different forms:
- Natural triglyceride oil: fatty acids bound as they occur in the fish.
- Ethyl ester concentrates: concentrated, with a higher EPA/DHA share per capsule.
- Re-esterified triglycerides: concentrated and converted back to triglycerides.
Which form is absorbed best is not settled. What counts is how much EPA and DHA the daily dose actually contains.
What to look for in fish oil
- EPA and DHA content: the label figure that matters is EPA plus DHA, not the amount of “fish oil”. Authorised EU claim: EPA and DHA contribute to normal heart function at 250 mg per day.
- Freshness: polyunsaturated fatty acids oxidise easily. Rancid oil smells and tastes unpleasant. Reputable makers report oxidation values, for instance in a certificate of analysis.
- Purity: sea fish can accumulate environmental contaminants. Controlled oils are tested for heavy metals and other contaminants.
- Amount: in 2012 EFSA saw no safety concerns for adults at supplemental intakes of up to about 5 g EPA and DHA per day.
Fish oil, fish or algae oil?
The German Nutrition Society recommends fish once or twice a week, including at least one portion of fatty sea fish. People who do not eat fish can use algae oil, which provides DHA and, depending on the alga, EPA. Plant oils such as linseed oil provide ALA, of which only a small share is converted to EPA and DHA.
General information, not medical advice. If you take anticoagulants, have surgery planned or are pregnant, discuss fish oil supplements with your doctor first. With cod liver oil, also mind the vitamin A and D content.