If you eat oily fish twice a week, skip the fish oil

If you eat two decent portions of oily fish most weeks, you probably don't need a fish oil capsule. If you eat oily fish roughly never — and most people do — then a capsule is a cheap, low-drama way to stop the gap being a canyon.

That's the whole decision. What follows is how to work out which one you're, and what to do about it without turning your kitchen into a laboratory.

What you're actually after

Fish oil isn't the point. Two specific fats in it are: EPA and DHA. They're the long-chain omega-3s your body uses in cell membranes, in the brain and retina, and in the signalling that dials inflammation up and down.

There's a third omega-3 you'll see on labels — ALA, from flaxseed, walnuts, rapeseed and chia. It's a genuine nutrient, but your body converts it to EPA and DHA at a poor rate. Ground flaxseed on your porridge is a fine habit. It isn't a substitute for the fish.

So when someone says "I get my omega-3s from nuts," they're half right and half not. The half that isn't right is the half that matters most.

The two-a-week benchmark

Public health guidance lands in much the same place on both sides of the Atlantic. The American Heart Association points to about two servings of fish a week. The NHS says at least two portions, one of them oily. A portion is roughly the size of your palm, or a small tin.

Oily means salmon, sardines, mackerel, herring, anchovies, trout, pilchards. Tinned counts. Frozen counts. Smoked counts.

Tuna is the one that trips people up. Fresh tuna is oily. Tinned tuna largely isn't — the canning process strips most of the long-chain omega-3 out. If your fish intake is four tins of tuna a week in sandwiches, you're getting good protein and not much of what we're talking about here.

Do the honest audit

Sit down and count the last fortnight. Not the fortnight you intend to have. The one you had.

Most men I know who insist they "eat plenty of fish" are describing a fish and chip supper, a tuna sandwich, and a salmon fillet their wife cooked. That's one qualifying portion in fourteen days.

If you land at four or more oily portions a fortnight, you're fine. Put the money somewhere else.

If you land at one or two, you've got two routes. Fix the food, or take the capsule, or — most realistically for someone with a job and school runs — do a bit of both and stop pretending you'll suddenly become a person who grills mackerel on a Tuesday.

Fixing the food is cheaper and easier than you think

This doesn't require cooking skill. It requires a shelf.

• Tinned sardines in olive oil. On toast with lemon and black pepper. Four minutes, start to finish, and cheaper than most protein bars.
• Tinned pink or red salmon. Mash with a fork, mayonnaise, a bit of mustard. Sandwich filling, jacket potato topping, done.
• Smoked mackerel fillets. Sold ready to eat. Flake into a jacket potato or over salad leaves. No cooking at all.
• Frozen salmon fillets. Oven from frozen, twenty-odd minutes, tray, foil, nothing to scrub.
• Anchovies. Not a meal, but melt two into a pan of tomato sauce and nobody will identify them.

Two of those a week and the supplement question goes away.

The obstacle is usually the family, not you. Kids often take against strong fish, and you'll get further with salmon fishcakes and mild smoked fish than with sardines on day one. Fine. Feed them what they'll eat, and eat the sardines yourself at lunch when nobody's watching.

If you're going to buy capsules, read the back

The front of the bottle says 1,000 mg. That's the weight of the oil, not the dose of what you want.

Turn it over and find the line for EPA and DHA. On a standard, inexpensive fish oil, the combined EPA and DHA in a 1,000 mg capsule is often somewhere around 300 mg. Concentrated products get considerably more into the same capsule and cost more per bottle, though often less per unit of actual omega-3.

That single habit — comparing on EPA and DHA, not on total oil — is most of the skill in buying this stuff. Two bottles at the same price can differ by a factor of three in what they deliver.

Also on the label: whether it's a triglyceride or ethyl ester form. Triglyceride form is generally regarded as better absorbed and costs a bit more. It's a real difference, not a big enough one to lose sleep over if the price gap is steep.

The things that actually go wrong

Rancidity. Omega-3s oxidise. A bottle that smells sharp and unpleasant when you open it, or capsules that taste aggressively of old fish, has gone off. Buy smaller bottles, check the date, keep them cool, and don't leave them in a car in July. Some people keep them in the fridge or freezer, which also blunts the repeat.

The burps. Take them with a proper meal, not on an empty stomach with a coffee. That fixes it for most people.

Cod liver oil confusion. It's not the same product. It carries vitamin A and vitamin D along with the omega-3, and vitamin A accumulates in the body in a way the others don't. Don't treat it as an interchangeable, higher-dose option, and don't stack it with a multivitamin without checking the numbers.

Mercury, if you're going the food route hard. Smaller fish are lower down the chain — sardines, anchovies, salmon, trout. Swordfish, shark and king mackerel are the ones with specific advice attached, particularly for pregnant women and young children. Official guidance exists and is worth reading if that applies to your house.

And one that isn't a side effect but a misunderstanding: fish oil is on the list of things to mention before surgery, and to raise with your doctor if you take blood thinners. That's a conversation with an actual clinician, not with me or a forum.

Don't expect it to do your recovery for you

This is where the supplement gets oversold. Fish oil isn't a training aid in the way creatine is. It won't add reps. The effects on muscle soreness that get discussed are modest and inconsistent, and they're nothing you'd notice next to the effect of an extra hour of sleep.

Think of it as nutritional insurance, in the same category as making sure you get enough vitamin D in winter. Insurance is useful. It isn't performance.

If you're tired, achy and stalling out, the honest order of operations is sleep, protein, consistent training you can actually repeat on a bad week, and then the small stuff. Fish oil is small stuff. Good small stuff, cheap small stuff, but it goes last.

And if you're pregnant, nursing, on medication, or managing a heart or liver condition, take the question to your GP or a registered dietitian rather than the internet. Doses that make sense for one person are wrong for another, and they can see your notes.

What I'd actually do

Buy a multipack of tinned sardines and a pack of smoked mackerel on your next shop. Eat two of them this week at lunch. See if it sticks.

If it does, you've solved it with food and you own no bottles. If by Thursday the tins are still in the cupboard and you've eaten a sausage roll at your desk three days running, buy the capsules, keep them next to the kettle, and take one with dinner.

Neither answer makes you a better man. Both of them are better than the third option, which is reading about this for another year and doing nothing.