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Can Cats Eat Fish?

Updated: August 11, 2022 by Kristen Chapple

Cats and fish. This is a combination that doesn’t make any sense when you think about it. One of the foods most of us feed to our cats is fish. But can cats eat fish? Is fish healthy for our little furry friends?

If you think about it from a natural point of view, cats eating fish doesn’t make sense. They don’t relate in any way. Cats don’t even like the water, not to mention fishing. The fish aquarium in your living room doesn’t count here. So why do we feed fish to our cats?

Can Cats Eat Fish?

From an evolutionary standpoint, cats aren’t equipped for fishing and their bodies weren’t made to eat fish. And that includes our domestic little friends. But you might have observed that cats can learn to love fish, if we feed it to them.

The only problem here is that fish isn’t actually good for cats for several reasons.


First, let’s talk about the quality of this meat used in pet foods. Most of the fish found in these cat canned food consists of actual leftovers of the fish industry all around the world.

These canned fish foods are just a hodgepodge high in magnesium and phosphorus, which can cause various problems in cats, even leading to kidney disease.


Fish is one of the most common cat allergen. It contains high levels of the protein called histamine which causes allergic reactions to most cats.

One study revealed that fish is the third most common allergen in cat foods, after beef and dairy products. If you think about it, none of these are present naturally in a cat’s diet. So maybe we shouldn’t feed our little furry friends something that they would never eat in their natural environment.

Thiamine Deficiency

Cats that eat primarily raw fish instead of special cat food are at risk for developing a condition called thiamine deficiency. This happens because fish in its natural state doesn’t contain thiamine, or vitamin B1 as it’s also called, and most canned fish food destined to human consumption doesn’t contain it either.

The lack of vitamin B1 for cats can result in serious problems.


Some research suggests that cat foods based on fish can lead to cats developing hyperthyroidism – a thyroid gland disorder – because of the PBDEs contained in those foods. PBDEs are chemicals used as flame retardants in many products such as furniture and building materials.

Ok, so what’s the link with fish? Well, fish accumulate and produce PBDEs in a natural way, which makes them dangerous for cats who consume fish-based foods on a daily basis.

Heavy Metals

Besides PBDEs, fish such as tuna and salmon can contain high levels of heavy metals – one of them being mercury – all of them toxic for humans, not to mention our little furry friends.

So if you usually use fish-based treats for your cat, make sure that fish is just a treat and not their main diet.

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