Whether mixed with mayonnaise and served in a sandwich, stirred into a pasta bake or dolloped on a baked potato, tuna is a simple yet versatile store-cupboard staple.

No surprise then that it's the second-most-eaten fish in the UK, with salmon taking the top spot.

And despite multiple scares about overfishing and high levels of mercury, sales of tuna have soared over the last two years.

Now figures released by Tesco have revealed how demand for the tinned fish has soared over the last two years. Sales are up nearly 18 per cent – the equivalent of more than two million kilograms.

According to Lee Bannerman, Tesco's tinned fish buyer, this increase is largely driven by a new health-conscious crowd on social media.

Carole Symons, nutritionist at Leon restaurants, says: 'One of the reasons tuna remains such a popular food is that it is convenient, affordable and versatile while still being nutritionally dense. 

'For many people, it offers an easy way to increase protein intake without relying on heavily processed foods.'

So just how healthy is tuna – and should we be concerned about eating too much of it?

What's so special about tuna?   

Twilight actor Robert Pattinson once admitted to eating tuna straight out of the can – such is his love for the tinned fish.

While its salty smell and association with cat food puts some people off, tuna is rich in Vitamin D, which is vital for healthy bones and muscles and selenium – a natural antioxidant that boosts the immune system. 

It also contains iron, needed for healthy blood, potassium for heart health, and omega‑3 fatty acids which help regulate inflammation, support brain function and help keep cells functioning properly.

Per 100g, tinned tuna in brine or spring water delivers between 25g and 30g of protein, less than 1g of fat and about 110 calories. If tinned in oil, there's the same amount of protein but about 6g of fat and 160 calories. 

Nutrition experts generally recommend low-calorie protein sources for a healthy diet. What's more, a tin is unlikely to set you back more than a pound. 

In tinned tuna less healthy than fresh? 

In the UK, skipjack – often labelled as 'tuna chunks' – makes up around 90 per cent of canned tuna sold, usually in brine, oil or spring water.

Albacore, or white tuna – often labelled as tuna steaks – contains more omega–3s than skipjack but also accumulates slightly more mercury. It is known for its firm, meaty texture and mild, buttery flavour.

While tinned tuna is generally more popular than fresh because of its affordability and long shelf life, fresh tuna comes with some extra health benefits. 

'The canning process squeezes out the natural oils – rich in DHA and EPA which are fats linked to brain and heart health – and often adds vegetable oils or brine which are less healthy,' says Dr Carrie Ruxton, dietitian and co–founder of SALT St Andrews gym.

Fresh tuna, such as yellowfin, bigeye and bluefin, is prized for its meaty texture and high concentration of heart-healthy omega-3s, as well as Vitamin D and B vitamins. 

Larger predatory species such as bluefin and bigeye are rich in healthy fats but also have higher levels of mercury and other pollutants – more on which later.

The canning process involves tuna being heated twice, first to separate the meat from the bones, and then a second time to sterilise it before the can is sealed. 

This process can damage heat-sensitive B vitamins, but there are still a decent amount left, and Vitamin D and mineral levels remain essentially unchanged. 

'Canned tuna can sometimes be the more practical and accessible option, which may help people consume more protein and less ultra-processed food overall,' adds Ms Symons.

Can you eat tuna every day?

The question of how often you can eat tuna remains a topic of debate among nutritionists and health experts.

The main concern is mercury. Tuna contains relatively high levels because of its position in the food chain, accumulating mercury from smaller fish and crustaceans.

Eating too much can lead to methylmercury poisoning, which affects the brain and nervous system. In adults, this may cause tingling, tremors and memory problems. It is especially risky during pregnancy and early childhood, when it can impact neurological development.

Dr Ruxton says: 'As some fish species, including tuna, can pick up contaminants, it's not advisable to eat them every day. However, there's no need to worry if you eat fewer than four 140g cans per week.'

The NHS recommends at least two portions of fish a week, including one oily fish. Fresh and frozen tuna count as oily fish, but canned tuna does not, as processing removes much of the oil.

Pregnant women or those trying to conceive should have no more than four cans or two tuna steaks per week.

There's no strict limit for healthy adults, but experts recommend variety. Nutritionist Ms Symons says two to three servings of lower-mercury tuna per week is a reasonable guideline, alongside other fish such as sardines, salmon and anchovies.

For vegetarians, Dr Ruxton suggests marine omega‑3 supplements derived from fish or algae.

Oil, brine or spring water? 

Tinned tuna usually comes packed in brine, spring water or oil, with the main difference coming down to taste preference and nutritional value. 

Tuna in spring water is the lightest option. Draining it removes some water-soluble omega-3s but it remains the top choice for calorie-conscious diets.

This option is best for recipes where you plan to add a creamy dressing anyway, such as a traditional mayonnaise-heavy tuna salad, tuna melts, or pasta casseroles. 

Tuna preserved in salty brine is similar in calories to spring water, but it is higher in sodium, which can raise blood pressure, while tuna in sunflower or olive oil is the highest in calories and fat.

Draining oil-packed tuna helps it retain its natural omega-3s better than draining water-packed tuna, as the good fats don't dissolve in the water.

This is best for dishes where the oil can be a feature, like a Mediterranean pasta, a Nicoise salad, or eating it on its own with crusty bread. Tuna packed in olive oil is widely regarded as the most flavourful.

Is tuna good for cholesterol? 

Tuna is generally considered a very heart–healthy choice and can be included in a cholesterol-conscious diet.

It contains moderate dietary cholesterol, typically around 30-50mg per 100g, depending on the species and preparation but medical consensus is that dietary cholesterol has a much smaller impact on blood cholesterol levels than saturated fats.

To keep your tuna dishes cholesterol–friendly, it's best to opt for tuna packed in spring water or brine instead of oil, and be mindful of high-fat condiments like standard mayonnaise.

What should you pair tuna with? 

To get the most out of tuna's health benefits, experts recommend pairing it with avocado, leafy greens, and whole grains to add fibre, carbohydrates, and healthy monounsaturated fats. 

Since tuna is a lean, protein-rich fish, these combinations create a perfectly balanced, filling meal that enhances your daily nutrition. 

Ms Symons says one of the healthiest ways to eat tuna is as part of a Mediterranean-style meal rather than in highly processed sandwiches or pasta dishes made with refined ingredients.