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What is tuna?

Tuna is a saltwater fish related to mackerel. There are around eight different commercial varieties that range in size from the small skipjack tuna to the large bluefin, and it is one of the most widely eaten fish in the world.

Tuna can be eaten fresh – either raw or cooked – and canned (which is always pre-cooked). Canned tuna in the UK is packed in brine, spring water or sunflower or olive oil.

Discover our full range of health benefit guides and find out more about the health benefits of other fish, including salmon. Also, check out some of our delicious tuna recipes, from our tuna & lemon pasta to sesame tuna steaks with Asian slaw.

Healthy tuna pasta with tomatoes and sweetcorn on a blue plate

Nutritional profile of canned and fresh tuna

From a macronutrient point of view, there isn't a great deal of difference in the amount of protein or fats when comparing canned tuna in brine to fresh. Fresh tuna is naturally higher in protein and contains a few more calories.

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A 100g serving of canned tuna (in brine) provides:

• 109 kcal / 460 kJ
• 24.9g protein
• 1.0g fat
• 69mcg selenium
• 0.733g salt

A 100g serving of fresh tuna (cooked) provides:

• 136 kcal / 579 kJ
• 32.3 g protein
• 0.8g fat
• 92mcg selenium
• 0.158g salt

When you buy tuna canned in oil, you can expect the fat content to increase to about 6.4g per 100g and the calories to be around 159 calories per 100g. When buying tuna, look for the Marine Stewardship Council Fisheries Standard (MSC) label, so you know the fish you are buying is certified sustainable.

Top 5 health benefits of canned tuna

1. Source of high-quality protein

Fish is a source of a high-quality protein, and canned tuna in particular offers an affordable protein source and makes a useful storecupboard staple.

2. Useful source of the amino acid taurine

As well as being a source of protein, seafood, including fish like tuna, is a useful source of the amino acid taurine. Studies suggest this amino acid may be helpful for protecting against heart disease.

3. Useful source of vitamins and minerals

Both fresh and canned tuna are a useful source of B vitamins, especially niacin (B3), which supports the nervous system and skin. Tuna also contains calcium, which supports healthy bones and muscle contractions; magnesium, required for energy; and vitamin D, which supports the immune system, bone strength and brain function. Fresh tuna (per 100g) has double the amount of vitamin D compared to that of canned tuna.

4. Low in fat

Tuna is low in fat, with just 1g of fat in a 100g edible portion – this is also the case for tuna canned in spring water or brine.

Although once considered an oily variety of fish, the type considered beneficial for heart health, the UK’s official advice on oily fish changed in 2018, with tuna no longer counting as a good source. This is because current data shows that levels of the long-chain omega-3 polyunsaturated fatty acids in fresh tuna are more comparable to that found in white fish.

5. May help weight management

Tuna, including canned tuna in spring water or brine, is low in fat and calories, but high in protein, making it a useful inclusion in a weight loss diet.

Tuna, asparagus & white bean salad in a large bowl

Is tuna, including canned tuna, safe for everyone?

A healthy, balanced diet should include at least two portions (two 140g cooked weight portions) of fish per week, of which one should be the oily variety. Most of us aren't eating this much.

That said, for certain types of fish including tuna, there are recommendations about the maximum amount you should eat. This is because tuna is at risk of contamination from mercury. Research suggests light and skipjack tuna are lower in mercury than larger species such as bigeye and albacore.

For this reason, the NHS recommends that if you’re pregnant or trying for a baby, you should not eat more than four cans of tuna or two tuna steaks per week. Otherwise, for the majority of us, tuna is fine to eat as part of a healthy, balanced diet.

Although an allergy to shellfish appears to be more common, some people are allergic to fish. Interestingly, some studies suggest canned tuna has a lower allergenicity. Despite this, if you know you are allergic to fish, you should avoid its consumption.

If an allergic reaction is suspected, make an appointment with your GP or NHS allergy clinic to confirm diagnosis.

For more information visit the NHS website for advice on allergies.

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Nicola Shubrook is a nutritional therapist and works with both private clients and the corporate sector. She is an accredited member of the British Association for Nutrition and Lifestyle Medicine (BANT) and the Complementary & Natural Healthcare Council (CNHC). Find out more at


All health content on is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional. If you have any concerns about your general health, you should contact your local healthcare provider. See our website terms and conditions for more information.

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