If you’ve ever tried to make a tuna mayo sandwich in the same room as a cat you could be well versed in just how much cats love tuna. Quite why cats go mad for this fishy treat has been explored by a new study looking at taste receptors in the mouths of our feline companions, and it’s revealed it's all to do with umami.
Cats are obligate carnivores, meaning they cannot survive or properly digest only plant material and must eat meat to survive. Umami, along with sweet, salty, sour, and bitter, make up the five basic taste sensations in mammals. Cats can’t taste sugar and rarely show a preference for sweet things because they lack the protein to sense it. They also have far fewer bitter taste receptors than humans.
This new research has revealed that not only do cats have the receptors for umami but these receptors are able to detect molecules found at high contractions in tuna.
To be able to detect umami, there are two genes that need to be present: in humans, both the Tas1r1 and Tas1r3 genes allow us to taste the umami flavor present in foods like mushrooms and soy sauce. Until now, only the Tas1r3 gene had been found in cats but this new research shows they also have the Tas1r1 gene, unlocking the reason they are so obsessed with tuna.
While there is some similarity between the receptor genes in cats and people, the team discovered a big twist in how these receptors actually work. Amino acids and nucleotides work in tandem to trigger the response. In people, amino acids bind to the receptors first and then the nucleotides come in. However, in cats, the nucleotides activated the receptors first, and then the amino acids were second.
“That’s the exact opposite of what we see in people” lead author Scott McGrane, a flavor scientist and research manager for the sensory science team at the Waltham Petcare Science Institute, told Science.
The team conducted an experiment where 25 cats were offered bowls of water with varying concentrations of amino acids and nucleotides and a bowl of plain water. Unsurprisingly, the cats preferred the bowls with higher concentrations of molecules found in umami-rich foods. Furthermore, the cats also preferred bowls containing high levels of histidine and inosine monophosphate (IMP), molecules that are both found in high levels in tuna.
Therefore, the team think the reason that cats love tuna so much is due to the specific combination of IMP and histidine that produces the strong umami taste preferred by cats. Just remember this next time you have to feed Felix.
The paper is published in Chemical Senses.