All about oily fish – a great source of lean protein and all sorts of added benefits

I am a great fan of oily fish. I avoid tinned tuna for conservation reasons, but I eat smoked mackerel for lunch at least 2-3 times a week; and ordinary fish at least once a week. In the summer, I buy and cook fresh mackerel (recipes on this site) as well as lovely fresh white fish from the famers market. Felicity Cloake makes compelling arguments here about the great health benefits of oily fish to boost our immunity and health, especially its Vitamin D content at this dark time of year. Read on!

On the scale of unappetising health foods, oily fish probably ranks somewhere between bone broth and blue-green algae. Fish is a hard enough sell in the UK as it is – all those spindly skeletons and googly eyes – without adding any malodorous fats to the equation. Indeed, so negative are the associations for some people that a friend swears blind that salmon and trout don’t count as oily fish on the basis that “they’re nice”. (Time for a rebrand, perhaps?)

The official recommendation of two portions of fish a week includes at least one oily variety; for the avoidance of doubt, that means anchovies, carp, eel, herring (and bloaters and kippers), mackerel, pilchards, salmon (tinned, fresh or frozen), sardines, scad (also known as horse mackerel or jack), sprats, swordfish, tuna (although not tinned), trout and whitebait, as well as fresh crab. And, lest you think you can get away with a mouthful of mackerel pate on a solitary cracker, a portion is roughly 140g cooked, or 170g raw fish – so, a tin and a half of sardines, or an average-sized chunk of salmon fillet. (Note that eel and swordfish are among those on the Marine Conservation Society’s list of fish to avoid, so it’s worth checking their website before striking out into new culinary waters.

 Because of concerns over levels of pollutants in oily fish, the government recommends not exceeding four portions a week, falling to two if you’re pregnant, likely to become pregnant (mercury remains in the body for several months after consumption) or breastfeeding. However, because there is some evidence of long-term cognitive benefits of fish consumption to the developing foetus, this is no reason to avoid it altogether.

Yet, pregnant or not, avoid it we do: according to a survey commissioned by Seafish, which represents the UK seafood industry, most UK adults eat just one portion of fish a week, of which only a third is oily, and most of it probably comes battered.

What is an oily fish, anyway?

The difference between oily and white fish is like that between long distance runners and couch potatoes, as the River Cottage Fish Book memorably said, and you may be surprised to learn that the fatty fish are the athletes here. Also known as “pelagic”, from the Greek word for ocean, because they are always on the move, herring, mackerel and their ilk spend their entire lives swimming in the direction of the next meal. Such an exhausting existence requires a ready source of fuel, and “the energy these fish need is saturated throughout their body tissues in the form of oil, ready to burn”.

People first started talking about this oil in relation to human health in the 70s, when Danish researchers studying Inuit populations noticed that, despite eating a blubber-heavy diet high in saturated fat, there was low incidence of heart disease. They suggested this may be thanks to a fatty acid, omega-3, which is found almost exclusively in oily fish (subsequent research suggests there may also be genetic factors at work), and it wasn’t long before a multibillion-dollar supplement industry was born. Little golden capsules are apparently rather more appealing to your average consumer than a plate of beady-eyed sprats.

Fish oil, we now know, is rich in the omega-3 fatty acids that are a vital part of our cell membranes and cell receptors and also play an important role in the production of hormones that control the thickness of the blood, the movement of artery walls, and regulate inflammation throughout the body. Yet, unlike other kinds of fat, our bodies cannot make them, but must take them from food: alpha-linolenic acid (ALA) is found in mainly vegetable sources such as nuts, seeds and oils, as well as leafy vegetables and some animal fats, while eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are mainly found in fish.

Of course, a mackerel is more than just its oil: according to the British Dietetic Association, oily fish are also a great source of lean protein and minerals such as iron, zinc, selenium and iodine, plus vitamins A and D – the last being particularly useful at this time of year, when most of us aren’t seeing much sunlight.

Fish oil or snake oil?

But bigger claims have been made for omega-3. As early researchers suspected, it seems to be good for the heart, helping to lower levels of triglyceride (fat in the blood), reduce inflammation and prevent clotting. Last year, scientists at Stanford University analysed data from 19 different studies involving more than 45,000 people from 16 countries and found that those with higher levels of omega-3 in their blood were about 10% less likely to die from a heart attack than those with lower concentrations. Not all studies have shown positive results, and indeed with advances in treatment in other areas, the effects may be less pronounced than in early experiments, but the evidence is still strong enough for Victoria Taylor, senior dietician at the British Heart Foundation to recommend eating oily fish “as part of a balanced diet to help protect our heart health”.

Fish oil is often associated with improved brain performance – cells with high levels of omega-3 in their membranes are better at communicating with other cells, which is important for brain function. However, trials on whether omega-3 supplements can reduce the risk of developing dementia have produced mixed results, and the Alzheimer’s Society concludes that although it is “likely that eating fish regularly as part of a balanced diet can improve your risk of age-related cognitive decline as well as other aspects of your health … the jury’s still out on omega-3”.

Further research is needed, but there is some evidence that omega-3 has both a protective effect on vision and beneficial effects on rheumatoid arthritis. And limited studies have also found that eating fish may reduce men’s chances of developing prostate cancer, and reduce the risk of mortality among bowel cancer sufferers. The same is true of a paper published last spring, which used mice to show that omega-3 fatty acids may reduce the harm caused by air pollution.

Capsules: easier to swallow?

Although much more work needs to be done to back up many of the claims made about omega-3 in particular, experts seem unanimous in their belief that oily fish are good for us. Dr Howard LeWine writes on the Harvard Health Blog: “If we could absolutely, positively say that the benefits of eating seafood comes entirely from omega-3 fats, then downing fish oil pills would be an alternative to eating fish. But it’s more than likely that you need the entire orchestra of fish fats, vitamins, minerals and supporting molecules, rather than the lone notes of EPA and DHA.”

There is also the obvious, yet still important fact that, if you’re eating more fish, you are probably eating less meat, which, for most of us, can only be a good thing.

Although supplements are the only solution for those who don’t eat fish (ones made from micro-algae are best for vegans), bear in mind that, unlike with a bad herring, which will make itself all too known, you won’t be able to smell when a capsule has gone rancid, so always look for the longest dated packet you can find and keep it out of direct sunlight. The rest of us would do better to cultivate a taste for oily fish instead. As Bee Wilson writes so wisely in This Is Not a Diet Book,: “If food habits are learned, they can also be relearned … even now you can readjust your preferences.”

Oily fish doesn’t have to mean tinned salmon or bloater paste if that’s what put you off in the first place; who could fail to love a crab bap, or a big bowl of spaghetti with sardines, chilli and lemon?

While researching oily fish, I have rediscovered the thrifty joy of Cornish pilchards mashed on toast, grilled a number of beautiful iridescent mackerel, and even sought out some deep-fried sprats – after all, batter or no batter, they count as one of my two a week. Fishy … but true.

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