In this article I would like to highlight the problems with giving tinned tuna to cats as their daily food. I am highlighting this issue because I come across it many times in my work as a cat behaviour consultant.

I will try to make this article simple and factual for ease of understanding and reading.

This article is not about wet food Vs kibble!

Let’s first start with what a cat needs nutritionally.


the problems with giving tinned tuna to cats as their daily foodCats are obligate carnivores: animals whose survival depends on animal flesh/muscle. This is where their nutrients are including one essential nutrient called Taurine. A wild cat’s prey contains high amounts of protein, moderate amounts of fat, and a minimal amount of carbohydrates, and their diet still requires these general proportions today. Cats also require more than a dozen other nutrients, including vitamins, minerals, fatty acids, and amino acids (1)

Their eating habits remain un-evolved like those of the wild cat. Cats occasionally eat grass but this is believed to be for the inducement of vomiting. Grass also contains an essential vitamin for cats, which is folic acid. Their jaws are designed to bite down and hold prey so they have limited side-to-side movement. This means that cats do not chew food! Their sharp teeth are designed to tear meat from bone. The diet of cats in the wild remains at 80% water content, which would be found in their prey. So, nutrients are found in all organs, bone and skin of the prey.

It is important to note that a totally muscle-based meat diet with no other ingredients would not be a healthy diet for a cat.


the problems with giving tinned tuna to cats as their daily foodSome clients, not many I must add, feed their cat daily amounts of human tinned tuna.  Tuna is not listed as a source of food that is toxic to cats but equally it is not a good food source to be feeding your cat daily. It does not contain the right nutrients for a start plus too much canned tuna can lead to mercury poisoning  for cats as stated by Cailin Heinze, a veterinary nutritionist (2).

Cailin states:

…..It seems reasonable to assume that when a cat eats tuna as its main diet, it ingests far more mercury on a body-weight basis than a human does—even a person who eats a lot of tuna.

Signs of mercury poisoning in cats—loss of coordination and balance, difficulty walking—can mimic other illnesses, including thiamine (a B vitamin) deficiency. Because mercury toxicity is not common in cats, it may not be the first thing a veterinarian suspects. So it’s possible that mercury poisoning happens, but is not diagnosed.


Tuna also has too much unsaturated fat and is not supplemented with Vitamin E or other antioxidants.

In terms of calorie content.When human foods are converted to kitty calories, it is easy to see that foods intended for humans have far too many calories for our feline companions. A few ounces of canned tuna in water contains almost 100 calories, which is more than a third of the recommended daily caloric intake for many cats. (3)

Therefore, tuna should not be fed as your cat’s primary source of nutrition although a small amount as a treat every once in a blue moon should not do any harm.



Researchers have noticed that cats with hyperthyroidism have higher levels of PCBs and PBDEs in their blood than cats without the disease. PCBs are found in fish. For more about the research in cats and eating fish you can click: HERE






the problems with giving tinned tuna to cats as their daily foodVitamin A: 

Crucial for a strong immune system and healthy vision, Vitamin A is a fat-soluble vitamin. This means that Vitamin A gets stored in fatty tissue or the liver (versus being excreted by the body like water-soluble vitamins). Too much Vitamin A in your cat’s diet can be toxic. Because of this risk, Vitamin A supplementation should be done cautiously and only under veterinary supervision.

Vitamin D: 

Vitamin D is a vital component of balancing and retaining calcium and phosphorus in your cat’s body. Vitamin D, also known as, “the sunshine vitamin,” aids in the proper functioning of bones, nerves, and muscles. Vitamin D is also fat soluble and should not be consumed in excess.

Vitamin B1 (Thiamine): 

Vitamin B1 is a water-soluble vitamin necessary for the healthy metabolism of carbohydrates, as well as the maintenance of normal growth and nerve impulse transmission.

Vitamin B2 (Riboflavin): 

Riboflavin is needed for growth and overall good health. It helps the body break down carbohydrates, proteins, and fats to produce energy and allows oxygen to be used by the body. This incredible vitamin helps contribute to the quality of your cat’s skin and coat. A lack of Vitamin B2 may cause adverse changes to your cat’s skin around the eyes and the abdomen.

Vitamin B3 (Niacin): 

This water-soluble vitamin is easily depleted through your cat’s urine and must be replaced regularly to maintain adequate levels. Vitamin B3 keeps your cat’s nervous system, gastrointestinal functions, and skin healthy.

Vitamin B6 (Pyridoxine): 

Vitamin B6 is also water soluble and part of the B vitamin group. There are 3 compounds that together are called Vitamin B6. Vitamin B6 cannot be stored in your cat’s muscle tissue, so they’ll need a constant source of vitamin B6 in order to maintain adequate levels. Vitamin B6 is important for healthy immune function and red blood cell function. The more protein that is consumed, the more B6 is required to metabolize it. It helps the body break down carbohydrates, proteins, and fats to produce energy and distribute oxygen. Signs of a vitamin B6 deficiency in cats include growth depression, convulsive seizures, and irreversible kidney lesions. B6 deficiency is rarely seen.

Look for a complete commercial food source for your cat’s needs or check out some of the commercial raw cat food companies. Just don’t feed your cat tinned tuna everyday!!

To find out more about cats and diet feel free to buy my book Let’s Talk About Cats. Chapter 11 focuses on our cat’s diet with expert advice from Dr Pete Coleshaw. Chapter 11’s cat chat is all about understanding the wording on our cat’s commercial food.








Anita Kelsey holds a first class honours degree in Feline Behaviour and Psychology (work based BA Hons) and runs a vet referral service dedicated strictly to the diagnosis and treatment of behaviour problems in cats. She is also a qualified cat groomer and specialises in grooming aggressive or phobic cats. Anita writes for Your Cat Magazine and is on their experts panel answering readers questions on cat grooming. She also advises on feline behaviour for the CFBA (Canine and Feline Behaviour) magazine as well as being a full member. Anita, a strong advocate of a vegan lifestyle, is based in London but consults all over the UK as well as international requests. She lives with her husband, a music producer, and two Norwegian Forest cats, Kiki and Zaza.

Her first book ‘Claws. Confessions Of A Professional Cat Groomer‘ was published by John Blake in 2017 with her second book, Let’s Talk About Cats just released on Amazon US and UK.