Is Canned Tuna Fish Bad for Cats?
Cat Food and Hydration

Is Tuna Safe for Cats to Eat?

If you’ve opened a can of tuna near your cat, you’ll know how magnetizing it can be. As cat owners, we love to treat our pets with delicious foods, but we also have to consider whether these foods are safe for our cat to consume.

Is tuna bad for cats? Tuna is a high-protein, tasty food that can be used to reward cats and stimulate their appetite. However, canned tuna is devoid of many vital nutrients so it should never be used as a meal replacement. If your cat enjoys tuna, feeding them a tuna-based “complete” cat food is the safest option. Tuna (in any form) also contains high levels of phosphorus and mercury so it shouldn’t be eaten every day.

One of the problems with tuna is that it can be very addictive. There’s no harm in giving your cat the occasional tuna-based treat, but you shouldn’t allow them to become dependent upon it. We’ll show you how to feed your cat tuna safely and responsibly.

Why Do Cats Love Tuna So Much?

You might find a few cats who are disinterested in tuna, but this is the exception rather than the rule; the majority of cats go wild for tuna. But why do cats have such a strong reaction to this fish?

  • Tuna has a strong, fishy smell that is very appealing to cats.
  • It also has a unique flavor that is entirely different from any white-fleshed fish.
  • It is high in protein.
  • Tuna is often served in brine or sunflower oil so cats can easily lap it up with their tongue. The brine or oil also takes on a strong, fishy flavor which is incredibly tasty for cats.
  • Tuna is usually given as a rare treat, so it is highly appreciated.

Unfortunately, foods that taste good are not always the healthiest.

Problems with Tuna for Cats

There is some disagreement regarding the safety of tuna for cats. Some resources warn that it is very dangerous to feed a cat tuna, whereas some vets would say that tuna is fine in moderation. Let’s discuss the potential problems with tuna:

  • Canned tuna (in brine) is very high in sodium. Consuming this food could lead to dehydration and urinary problems – especially in senior cats
  • Tuna is relatively high in phosphorous, so it is not suitable for cats with kidney disease
  • Some forms of tuna contain the enzyme thiaminase, which destroys thiamine (vitamin B1). This could result in vitamin B1 deficiency
  • Tuna is low in taurine (vital amino acid for cats), so it is not a complete meal
  • Canned fish contains mercury
  • Canned tuna may provide cats with too much selenium
  • One study showed that a tuna-rich diet caused inactivity, lethargy, weight loss, and hunger
  • Research shows that cats may develop a vitamin E deficiency when fed a tuna-rich diet. This is because tuna is high in polyunsaturated fats

As we’ll explore, some of the above issues can be avoided if you feed your cat a particular type of tuna, though it’s fair to say that all types of tuna have the potential to cause harm.

Benefits of Tuna for Cats

Tuna does have some health benefits that are worth mentioning here. For example:

  • It smells incredible so it can stimulate a cat’s appetite if they are reluctant to eat.
  • It is high in the amino acid lysine (essential for cats).
  • It contains docosahexaenoic acid (DHA) – to support brain and eye health.
  • It is a lean, high-protein product – In the wild, a cat’s diet is high in protein and would have moderate amounts of fat.

The list of potential problems is longer than the list of potential benefits, so this does mean that you need to be extra cautious if you choose to feed tuna to your cat.

Best Types of Tuna for Cats

Tuna comes in different forms, some of which are safer for cats to consume. If you don’t want to deny your cat their favorite fishy treat, here are the best types of tuna for cats:

why you shouldn't feed your cats tuna

1) Canned or Cooked Tuna

Although raw food has some benefits, you should not feed raw tuna to a cat. Raw tuna contains thiaminase (an enzyme that destroys thiamine – vitamin B1).

The canning/cooking process destroys this enzyme so canned/cooked tuna is less likely to cause a vitamin B1 deficiency than raw tuna.

2) Tuna in Spring Water

If you feed your cat canned tuna, make sure it’s in spring water rather than brine (salt water) or sunflower oil.

The levels of sodium found in brine may cause dehydration, and sunflower oil may cause diarrhea.

3) Low-Mercury Tuna

Due to water pollution, all fish and shellfish contain mercury. However, large, long-living fish (such as albacore or bluefin tuna) tend to contain higher levels of mercury than smaller fish.

You can opt for a lower-level mercury product but choosing chunk light tuna. This product is made from smaller tuna fish such as Skipjack and Tongol.

These fish live in shallower waters and will have consumed less prey throughout their lifetime so the mercury concentrations in their bodies will be lower.

According to Science Alert, farmed tuna may contain lower levels of mercury than wild caught fish so purchasing farmed tuna could also be an option.

4) Tuna-Based Cat Foods

If you are concerned about the health risks of canned tuna, the best thing to do would be to purchase some tuna-flavored cat food.

As mentioned, canned tuna is not a balanced meal because it contains very low levels of taurine (vital for cats’ wellbeing). Instead, choose a “complete,” nutritionally-balanced cat food that contains tuna on the ingredients list.

How to Get the Nutritional Benefits of Tuna

As mentioned, the safest way to feed your cat tuna is to offer them a good-quality complete pet food that contains tuna. That way, your cat will benefit from the high levels of docosahexaenoic acid (DHA) in tuna, but they’ll still be eating a nutritionally-balanced meal.  

Moreover, tuna-flavored cat food still smells and tastes like tuna, so it is great for cats who crave tuna, or cats with a poor appetite.

But if your cat is not too fussed about the taste of tuna, you can find docosahexaenoic acid (DHA) in other foods, too. For example, some pet food manufacturers add this beneficial fatty acid to poultry-based cat foods or even vegetarian cat foods.

Thanks to technology advancements, the most beneficial component of tuna – docosahexaenoic acid – can now be found in other foods, so, if you want to get the benefits of tuna, look out for cat food that contains DHA.

How to Feed your Cat Tinned Tuna Safely

As mentioned, the safest way to feed your cat tuna is to offer them tuna-based cat food. But does this mean should never feed your cat tinned tuna? In reality, the occasional serving of tinned tuna is unlikely to cause harm to your cat, as long as you remember the following:

1) It’s Not a Meal Replacement

Canned tuna should never be given as a meal replacement because it is not nutritionally balanced. It’s OK to treat your cat with a few chunks of canned tuna, but this should be in addition to their regular meals.

2) Don’t Encourage Addiction

It’s OK to “treat” your cat with tasty foods like tuna but make sure you are giving them alternative “treats” too. This should stop them from becoming addicted to tuna.

Try feeding your cat specially formulated cat treats some of the time, or even try “treating” them in other ways. For example, try petting or playing with your cat when they beg for extra food.

3) Use Tuna to Entice your Cat

If your cat is reluctant to eat and you want to use tuna to stimulate their appetite, break up a few pieces of “chunk light” tuna and sprinkle on top of their meal.

Canned tuna is not all bad – it can be really useful for helping senior cats or stressed cats to regain a healthy appetite.

4) Give Sparingly

Do not give your cat canned tuna more than once a week.

5) Not Suitable for all Cats

If your cat has a chronic health condition such as kidney disease, you should not feed them canned tuna – more on this later.

If you follow these tips, it is unlikely that the occasional portion of tinned tuna would cause any health problems. Nevertheless, keep a close eye on your pet’s health to check their diet is not having any adverse effects.

Signs your Cat Is Overeating Tuna

Some of us are guilty of overfeeding our pets or giving them a few too many treats. It isn’t easy to say no to cats when they are begging for a few bites of their favorite food.

When it comes to tuna, you should try your very best not to overfeed your cat. As mentioned, a small portion of tuna once per week should not have any adverse effects but any more than this might (especially if your cat eats cat food/treats containing tuna as well).

But how would you know if your cat is eating too much tuna? According to a study by Taylor and Francis, the following symptoms seem to be caused by a tuna-rich diet:

  • Urinary Problems
  • Lethargy
  • Less Vocal
  • Increased Appetite – Perhaps due to the addictive nature of tuna or perhaps because it lacks many essential vitamins and minerals.
  • Weight Loss
  • Drinking Excessively – As some forms of tuna are high in salt.
  • Wounds Slow to Heal – Related to vitamin E deficiency.

These symptoms can be due to other things besides a tuna-rich diet. Nevertheless, if you suspect you are feeding your cat too much tuna, you should reduce the amount immediately and feed them only high-quality, complete cat food until you see improvements.  

Times You Should Never Feed a Cat Tuna

Due to the risks associated with feeding a cat tuna, there are specific scenarios in which cats should never be fed tuna. If your cat has one of the following illnesses, do not feed them canned tuna and make sure any tuna-based cat food is safe for them to eat:

1) Kidney Problems

Although cats with kidney disease benefit from high-quality, digestible protein, human-grade canned tuna is not suitable because it is high in phosphorous.

A diet high in phosphorous which will speed up the development of kidney disease. Renal cat food tends to contain rabbit because this meat is naturally low in phosphorous.

2) Heart Disease

Cats with heart disease are typically fed very low sodium and high taurine diet. Canned tuna is generally high in sodium and low in taurine, so it is not in any way suitable.

3) Diabetes

Tuna in brine is unsuitable for cats with diabetes as it will cause dehydration.

is tuna dangerous for cats?

4) Fish Allergies

Tuna allergy is not uncommon in cats. Symptoms include intense scratching, flatulence, hyperactivity, and vomiting. Allergies are sometimes hard to diagnose, especially if a cat eats a mix of cat food, treats, and leftovers.

If you have noticed any digestive issues in your cat, it’s possible that the occasional lick of tuna is to blame. If you suspect a food allergy in your cat, you would usually start eliminating foods one by one to determine which food is to blame.

Mercury Poisoning from Tuna in Cats

Over the last decade, we’ve heard about the dangers of fish and mercury poisoning (metal poisoning). Does pet food contain too much mercury, and should we be concerned about mercury poisoning symptoms from seafood-based pet foods?

In this report on Science Direct, experimenters tested the mercury levels in 101 pet foods and here’s what they found:

  • Mercury was present in all the samples
  • 14 of the 101 samples had abnormally high levels of mercury compared to the rest (greater than 100ng g‐1)
  • Foods containing tuna and prawn had the highest concentrations of mercury
  • Two samples of the same cat food from different batches had different amounts of mercury

None of the samples exceeded the World Health Organization’s (WHO) limit for safe consumption of fish for humans (which is 1000 ng g‐1).

However, there is no guidance on the safe upper limit of fish consumption for cats, so we cannot conclude that these levels of mercury are healthy and safe. At the same time, there is insufficient evidence to say they are very dangerous, either.

Mercury toxicity is not commonly seen by vets, but that doesn’t mean that minor, gradual damage isn’t being caused by moderate levels of mercury in our pets’ diets.

Until further research is conducted, it is really hard to say whether the mercury levels in tuna and tuna-based cat food are harmful to your cat.

If you are concerned, you could limit canned tuna to once a week (and tuna-based cat foods to 1-2 times per week) or perhaps even eliminate tuna from your cat’s diet completely.

Cat Addicted to Tuna (Advice and Tips)

Over time, cats can develop an unhealthy addiction to tuna. For example, some cats may become extremely fussy around food and refuse to eat anything besides tuna. Other cats may even become aggressive if they don’t get their tuna fix. Here’s how to handle a cat that’s addicted to tuna:

Canned Tuna vs. Tuna Cat Food

Introduce cat foods with other flavors. Rabbit is fairly strong-tasting and low in phosphorous, so it’s a healthy alternative.

Avoid Tuna Chunk Treats

If you give your cat small chunks of tuna as a “treat” try replacing these treats with tuna-flavored treats, a small piece of cooked chicken, or another flavored treat specially formulated for cats.

Start treating your cat in other ways. For example, when they’re looking around for something to nibble on, try giving them some attention – try petting them or playing with them.

Remove all sources of tuna until your cat is eating other foods. If your cat refuses other food for more than 24 hours (despite you offering them some variety to choose from), you should take them to the vet for an examination.

Is It OK to Feed My Cat Tuna Occasionally?

While tuna is high in protein and incredibly tasty, it can be high in salt, low in essential nutrients, and contains higher levels of mercury than many other foods.

If you know your cat enjoys the occasional tuna treat, all this negative information might leave you feeling a bit disheartened. What are you supposed to treat your cat with now? Well, as long as your cat is in good health, most vets would agree that the occasional tuna treat is OK.

The safest way to give your cat tuna is to choose a tuna-based pet food or cat treat. Giving them a few chunks straight from the tin is OK, too, but it should never be used as a meal replacement.

Remember that although food-based treats are nice, one of the kindest and healthiest ways to treat your cat is to give them love and attention. That way, you’ll build a stronger bond with your pet and discourage any potential food addictions in cats.