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In fact, fish is not a natural food for cats. They are obligate carnivores, meaning they need a meat diet to be healthy.
Their ancestors, wild cats, lived in deserts and steppes, hunting small rodents and birds. How could they get fish there? Okay, in some regions, cats could live in areas with water bodies, but they, with rare exceptions, cannot catch fish.
Nevertheless, cats love fish, especially tuna. Look at the composition of a cat's favorite food and you will most likely find tuna. In articles for cat owners, veterinarians advise disguising pills with minced tuna.
A recent study conducted by a group of scientists from the UK, Germany, and the US identified the best flavor for cats and the molecular mechanism for recognizing it.
It turned out to be the umami flavor - also called the "fifth taste". It is not sour, salty, sweet, or bitter. It is usually described with the words "spicy," "brothy," or "meaty." Imagine two identical soups, the first of which is made with water and the second with meat broth. This second soup will taste like umami.
In humans, two genes, Tas1r1 and Tas1r3, are responsible for the sense of umami flavor. Until recently, it was known that cats have only one of them. The presence of the second component was proved in a new study by examining the taste buds of the cat's tongue. It was also found that feline receptors differ from human receptors structurally and functionally: in humans, the receptor is activated by amino acids, and nucleotides enhance this response. In cats, on the contrary, the receptor is activated by nucleotides and enhanced by amino acids.
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Finally, the experimenters offered their subjects two bowls of water to which they added different combinations of umami flavors. The most appealing was the one containing histidine and inosine monophosphate, compounds that are found in particularly high amounts in tuna.
This coincides with the personal experience of Yasuka Toda, a molecular biologist at Meiji University and a leader in the study of the evolution of umami taste in mammals and birds. When she was a veterinary student, she restored appetite in cats that had lost it by sprinkling dried flakes of bonito fish, a close relative of tuna, on their food.
So can cats be given fish and how much?
You can, but in moderation. It is definitely not worth switching to a complete fish diet: fish contains too much phosphorus and not enough calcium. But a few pieces of fish once or twice a week is quite acceptable.
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