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 reduce your risk of 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 or fish liver oil supplements.
What are omega-3 fatty acids?
Omega-3 fatty acids are essential fats we need to get from diet, as the body can’t make them from other fats we eat. There are three main omega-3 fats in our diet:
- Alpha-linolenic acid (ALA) - this is the plant version of omega-3 fats
- Eicosapentaenoic acid (EPA)
- Docosahexaenoic acid (DHA)
Long-chain omega-3 fats – EPA and DHA – have been shown to have positive health benefits in reducing the risk of heart disease and stroke. In the absence of dietary EPA or DHA, the body can convert ALA into DHA but the process is not very efficient. First, the ALA goes through a process of being lengthened and reconfigured, initially forming EPA which can then be converted into DHA. 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 long chain omega-3 fats EPA and DHA 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 and toxic polychlorobiphenyls (PCBs) that need to be avoided in pregnancy.
Some white fish also contains omega 3, but in much smaller quantities. These include:
- Dover sole
- Red mullet
ALA is found in vegetable oils, nuts, seeds and green leafy vegetables. Rapeseed oil, often called cooking oil in the supermarket, is 10% ALA content by weight. Flaxseed (linseed) oil is two-thirds ALA, but with such a high omega-3 content it isn’t as stable as rapeseed oil when it comes to storage. Nuts rich in ALA include walnuts and pistachio, and green leafy vegetables. Hemp milk is also rich in omega-3 fats.
Some foods may be fortified with extra omega-3, including some eggs, breads and spreads.