Omega-3 fatty acids
The health benefits claimed for foods often come with little or no firm evidence. That's not the case for omega-3 from oily fish.
There's evidence that eating the recommended two portions of fish a week, including one oily fish dish, may help with maintaining healthy blood pressure and blood lipids, which in turn may help prevent heart disease.
Studies have shown people in countries with more fish and omega-3 in their diets have a lower risk of heart disease.
Some types of omega-3 are also found in vegetables and oils, and some people take omega-3 supplements, often in the form of fish oil.
What are omega-3 fatty acids?
Omega-3 fatty acids are a group of three fats:
- Alpha-linolenic acid (ALA). The body can't make this on its own, so it comes from the food we eat.
- Docosahexaenoic acid (DHA).
- Eicosapentaenoic acid (EPA)
Once eaten, the body turns ALA into DHA and EPA, though not very efficiently - some estimates say the conversion is as low as 5%. So many dietitians recommend we focus most of our efforts on consuming DHA and EPA fatty acids.
Sources of omega-3 fatty acids
Good oily fish sources of omega-3 include:
- Tuna (fresh or frozen, some canning processes removes omega-3)
- Crab (fresh)
Shark, swordfish and marlin should be avoided in pregnancy and before getting pregnant because they may contain mercury that's damaging to growing babies.
Some white fish also contains omega 3, including:
- Dover sole
- Red mullet
ALA is found in vegetable oils, including rapeseed and linseed, nuts, including walnuts and pistachio, and green leafy vegetables.
Some foods may be fortified with extra omega-3, including some eggs, milk, yoghurt, bread and spreads.
There are no current guidelines recommending omega-3 supplements, as it is best to get omega-3 from food if possible.
If you do decide to take an omega-3 supplement, the British Dietetic Association (BDA) advises looking for omega-3 oil rather than liver oil and making sure the supplement is appropriate for the age of the person taking it. Seek medical advice if unsure.
The BDA advises adults not to take more than around 450mg EPA and DHA a day.
Some omega-3 supplements also contain vitamin A, and the total amount of vitamin A a person has a day from food and supplements combined shouldn’t exceed 1.5mg.
Vitamin A supplements should be avoided in pregnancy and for women planning a pregnancy.