Articles · Nutrients
Oily fish and omega-3: how much is enough?
Why oily fish is singled out in heart-health advice, how much to eat each week, what pregnant women should watch, and where vegetarians can find omega-3.
· 3 min read
Nutrition advice changes, but one recommendation has stayed remarkably steady for decades: eat fish twice a week, and make one of them oily. Why oily fish, what does "oily" mean, and what if you don't eat fish at all?
What's special about oily fish?
Oily fish such as salmon, trout, mackerel, herring, sardines, pilchards and anchovies carry their fat in their flesh, and that fat is rich in two long-chain omega-3 fats: EPA and DHA. The body uses them in cell membranes, especially in the brain and the eyes, and they help regulate heart rhythm, inflammation and blood fats.
White fish such as cod and haddock store most of their fat in the liver, so their flesh has much less. (In the UK, tuna isn't counted as oily fish, though fresh tuna has some omega-3.)
Think about it: When did you last eat oily fish? Was it this week, this month, or can't remember?
What's the evidence?
A major review in 2006 weighed the benefits of eating fish against the risks of contaminants. It concluded that eating fish once or twice a week, especially species rich in EPA and DHA, lowered the risk of dying from coronary heart disease by about 36%, and the risk of dying from any cause by about 17%. For most people, the authors found, the benefits far outweighed the risks.
How much is enough?
- Most adults: at least two portions of fish a week (a portion is about 140 g cooked), one of which is oily.
- Pregnant women, and women who may become pregnant: no more than two portions of oily fish a week, because of small amounts of pollutants. Avoid shark, swordfish and marlin, and limit tuna.
- Children: fish is a good food for them too; follow the same limits on the large predatory fish.
Fish (Still Life), Édouard Manet, 1864, Art Institute of Chicago. Fish laid out on a kitchen table, painted by Manet in 1864 with quick, confident strokes. Look at the silvery skins: the shine is mostly paint, and in an oily fish, the goodness is mostly in the fat. Public domain · Wikimedia CommonsNo fish? Other sources
- Plants such as flaxseed (linseed), chia seeds, walnuts and rapeseed oil carry a different omega-3, called ALA. It's good for you, but the body turns only a small share of it into EPA and DHA.
- Algae oil supplements provide EPA and DHA directly. That's where fish get theirs, and it's suitable for vegetarians and vegans.
- Fish oil supplements are an option, but whole fish brings protein, vitamin D, iodine and selenium too. Ask a doctor before taking high doses, especially if you take blood thinners.
Try this: Canned fish counts. A tin of sardines, mackerel or salmon costs little, keeps for years and makes a quick lunch: on toast, in a salad, or stirred through pasta with lemon and parsley.
Think about it: Which of your regular meals could swap meat for oily fish once a week?
Quick quiz
Which of these is an oily fish: cod, mackerel or haddock?
Mackerel. Cod and haddock are white fish that store their fat mainly in the liver.
How many portions of fish a week do most guidelines recommend?
At least two, one of them oily.
Why can't walnuts and flaxseed fully replace oily fish?
Their omega-3 is ALA, and the body turns only a small share of it into the EPA and DHA found in fish. Algae oil provides EPA and DHA directly.
Sources
General information, not medical advice. If you have a health condition, are pregnant or take medication, ask a doctor or dietitian what is right for you.