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, it won’t be long before your cat shows an interest. We love to treat our pets with delicious foods, but also have to consider whether this type of fish is safe for cats.

Is tuna bad for cats? Tuna contains high levels of phosphorus and mercury, so it should never be eaten daily.  It is high in protein, but lacks many essential nutrients. Feeding your cat a scientifically-formulated tuna cat food is the safest option.

Tuna can become addictive to cats due to the texture and strong aroma. There’s no harm in giving your cat an occasional tuna-based treat, but it should be fed to cats in moderation and infrequently.

Why Do Cats Love Tuna So Much?

You may find some cats that are disinterested in tuna, but they will be the exception to the rule. So, why do cats have such a strong reaction to this fish?

  • Tuna has a strong, fishy smell that is very appealing to cats.
  • It has a unique flavor that is completely different from any white-fleshed fish.
  • It is high in protein. Cats are obligate carnivores.
  • Tuna is often served in brine or sunflower oil, so cats can easily lap it up with their tongue. The brine or oil also has a strong, fishy flavor which is very tasty for cats.
  • Tuna is usually given infrequently as a treat, so it’s something that cats look forward to eating.

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

Why Tuna is Bad for Cats

There is disagreement regarding the safety of tuna for cats. Some experts warn that it is harmful to feed a cat tuna, whereas some experts claim that tuna is OK in moderation. We’ll start by looking at why tuna is bad for cats:

  • 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 quite 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, according to Vet Specialists.
  • Tuna is low in taurine. This is a vital amino acid for cats, so it is not a complete meal.
  • Canned fish contains mercury, which is toxic to cats.
  • Canned tuna may provide cats with too much selenium.
  • A tuna-rich diet can lead to inactivity, lethargy, weight loss, and hunger.
  • Cats may develop a vitamin E deficiency, due to polyunsaturated fats, when fed a tuna-rich diet.

Some of the above health issues can be avoided if you feed your cat a particular type of tuna, although all types of tuna have the potential to cause your cat harm.

Health Benefits of Tuna for Cats

Tuna does have some health benefits. These include:

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

Best Types of Tuna for Cats

Some forms of tuna are safer for cats to consume. If you don’t want to deny your cat her favorite fishy treat, here are the healthiest ways to feed tuna to your cat:

why you shouldn't feed your cats tuna

1) Canned or Cooked Tuna

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

The canning/cooking process destroys thiaminase, so canned and cooked tuna is less likely to cause a vitamin B1 deficiency in cats 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 sodium in brine can cause dehydration, and sunflower oil can cause diarrhea.

3) Low-Mercury Tuna

Due to water pollution, all fish and shellfish contain some mercury. However, large and long-living fish, such as albacore or bluefin tuna, 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 significantly lower.

According to Science Alert, farmed tuna may contain lower levels of mercury than wild-caught fish so getting farmed tuna is another excellent option.

4) Tuna-Based Cat Foods

If you’re concerned about the health risks of canned tuna, it’s recommended that you get some tuna-flavored cat food.

Canned tuna is not a balanced meal because it contains low levels of taurine. Instead, choose a “complete,” nutritionally-balanced cat food that contains tuna on the ingredients list.

How to Maximize the Nutritional Benefits of Tuna

The safest way to feed your cat tuna is through a ‘complete’ pet food that contains tuna. That way, your cat will benefit from the high levels of docosahexaenoic acid (DHA) in tuna, but she’ll still be eating a nutritionally-balanced meal.

Moreover, tuna-flavored cat food still smells and tastes like tuna, so it’s ideal for cats who crave tuna, or cats with a poor appetite. You can find docosahexaenoic acid (DHA) in other foods. For example, some pet food manufacturers add this fatty acid to poultry-based and vegetarian cat foods.

Due to technology advancements, the most beneficial component of tuna (docosahexaenoic acid) can now be found in other foods. If you want your cat to enjoy the health benefits of tuna, then you should look for a type/brand of cat food that contains DHA.

How to Feed your Cat Tinned Tuna Safely

The safest way to feed your cat tuna is to offer them tuna-based cat food. But, does this means that you should never feed your cat tinned tuna? The occasional serving of tinned tuna is unlikely to cause any harm to your cat, as long as you remember the following things:

1) It’s Not a Meal Replacement

Canned tuna is not a meal replacement because it’s not nutritionally balanced. It’s OK to treat your cat with a few chunks of canned tuna, but this should be in addition to her regular meals.

2) Don’t Encourage Addiction

It’s OK to “treat” your cat with tasty foods, like tuna. But make sure that you’re giving her alternative “treats” too. This should stop your cat from becoming obsessed with eating tuna.

Try feeding your cat specially-formulated cat treats or “treating” her in other ways. For example, try petting or playing with your cat when she used her manipulative skills to 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 her appetite, break up a few pieces of “chunk light” tuna and sprinkle this on top of her meal.

Canned tuna can be really useful for helping stressed or senior cats to regain their 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 her canned tuna. It’s unlikely that the occasional portion would cause any health problems.

Signs your Cat is Eating Too Much Tuna

Some of us are guilty of overfeeding our pet or giving her too many treats. It isn’t easy to say no to a cat when she’s begging for her favorite fish-based food. You should avoid overfeeding your cat.

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

  • Urinary Problems
  • Lethargy
  • Less Vocal
  • Increased Appetite 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 due to a vitamin E deficiency.

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

1) Kidney Problems

Although cats with kidney disease do 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.

Here’s some further information on the type of protein that cats need.

2) Heart Disease

A cat with heart disease is fed a low sodium and high taurine diet. Canned tuna is 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

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

If you have noticed any digestive issues in your cat, it’s possible that the occasional piece of tuna is to blame. If you suspect a food allergy, you should 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 cat 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 100 ng 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.

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.

If you’re 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

Over time, cats can develop an unhealthy addiction to tuna. For example, some cats may become extremely fussy about food and refuse to eat anything besides tuna. Other cats may 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 to tuna fish for cats.

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.

Start treating your cat in other ways. For example, when she’s looking around for something to nibble on, you should give her some attention. Try petting or playing with her.

Remove all sources of tuna until your cat is eating other foods. If your cat refuses other food for more than 24 hours, you should take her to the vet for an examination.

Is It OK to Feed My Cat Tuna Occasionally?

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

If you know your cat enjoys the occasional tuna treat, all this negative information might leave you feeling a bit disheartened. As long as your cat is in good health, an 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, but it should never be thought of as a meal replacement.