Why do cats love tuna so much? Scientists may finally know

science.org ^

[algore]

Apart from Garfield’s legendary love of lasagna, perhaps no food is more associated with cats than tuna. The dish is a staple of everything from The New Yorker cartoons to Meow Mix jingles—and more than 6% of all wild-caught fish goes into cat food. Yet tuna (or any seafood for that matter) is an odd favorite for an animal that evolved in the desert. Now, researchers say they have found a biological explanation for this curious craving.

In a study published this month in Chemical Senses, scientists report that cat taste buds contain the receptors needed to detect umami—the savory, deep flavor of various meats, and one of the five basic tastes in addition to sweet, sour, salty, and bitter. Indeed, umami appears to be the primary flavor cats seek out. That’s no surprise for an obligate carnivore. But the team also found these cat receptors are uniquely tuned to molecules found at high concentrations in tuna, revealing why our feline friends seem to prefer this delicacy over all others.

“This is an important study that will help us better understand the preferences of our familiar pets,” says Yasuka Toda, a molecular biologist at Meiji University and a leader in studying the evolution of umami taste in mammals and birds. The work could help pet food companies develop healthier diets and more palatable medications for cats, says Toda, who was not involved with the industry-funded study.

SIGN UP FOR THE SCIENCEADVISER NEWSLETTER The latest news, commentary, and research, free to your inbox daily Sign up Cats have a unique palate. They can’t taste sugar because they lack a key protein for sensing it. That’s probably because there’s no sugar in meat, says Scott McGrane, a flavor scientist and research manager for the sensory science team at the Waltham Petcare Science Institute, which is owned by pet food–maker Mars Petcare UK. There’s a saying in evolution, he says: “If you don’t use it, you lose it.” Cats also have fewer bitter taste receptors than humans do—a common trait in uber-carnivores.

But cats must taste something, McGrane reasoned, and that something is likely the savory flavor of meat. In humans and many other animals, two genes—Tas1r1 and Tas1r3—encode proteins that join together in taste buds to form a receptor that detects umami. Previous work had shown that cats express the Tas1r3 gene in their taste buds, but it was unclear whether they had the other critical puzzle piece.

So McGrane and colleagues biopsied the tongue of a 6-year-old male cat that had been euthanized for health reasons unrelated to the study. Genetic sequencing revealed his taste buds expressed both the Tas1r1 and Tas1r3 genes—the first time scientists showed that cats have all the molecular machinery needed to detect umami.

When the researchers compared the protein sequences encoded by these genes with those of humans, however, they found a striking difference: Two critical sites that allow the human receptor to bind to glutamic and aspartic acid—the main amino acids that activate umami taste in people—were mutated in cats. “So I began thinking, maybe cats can’t taste umami,” McGrane says.

To double check, he and his team engineered cells to produce the cat umami receptor on their surface. They then exposed the cells to a variety of amino acids and nucleotides. The cells did respond to umami—but with a twist. In people, the amino acids bind first and the nucleotides amplify the response. But in cats, the nucleotides activated the receptor, and the amino acids further boosted it, McGrane says. “That’s the exact opposite of what we see in people.”

In the last part of the experiment, McGrane and colleagues gave 25 cats a taste test. In a series of trials, they presented the felines with two bowls of water, each with various combinations of amino acids and nucleotides, or just water alone. The cats showed a strong preference for bowls that contained molecules found in umami-rich foods, suggesting this flavor—above all others—is the primary motivator for cats.

“I think umami is as important for cats as sweet is for humans,” Toda says. Dogs, she notes, can taste both sweet and umami, which may explain why they’re not such fussy eaters.

But it wasn’t just umami in general the cats craved. The felines showed a particular preference for bowls containing histidine and inosine monophosphate—compounds found at particularly high levels in tuna. “It was one of the most preferred combinations,” McGrane says. “It really seems to hit that umami sweet spot.”

That jibes with Toda’s personal experience. When she was a veterinary student, she got cats with no appetite to eat by sprinkling their food with dried flakes of bonito—a common umami ingredient in Japan and a close relative of tuna. “It worked very well!” she says.

Indeed, one application of the work could be developing foods that are more palatable to cats, McGrane says. He also thinks a spoonful of umami (figuratively speaking) could help feline medications go down easier—welcome news for anyone who’s almost lost a finger trying to pill a cat.

Why cats have a hankering for tuna in the first place remains a mystery. They evolved in the deserts of the Middle East about 10,000 years ago, where fish of any kind was unlikely to be on the menu.

It may have been a taste cats developed over time. As far back as 1500 B.C.E., cats are depicted eating fish in the art of Ancient Egypt. And by the Middle Ages, felines in some Middle Eastern ports were consuming large quantities of fish—including tuna—likely because they were feasting on the scraps left by fishers. In both cases, cats that evolved a taste for fish—and perhaps tuna in particular—may have had an advantage over their comrades, says Fiona Marshall, a zooarchaeologist at Washington University in St. Louis.

“We’re at a starting point—it’s not a finished story,” McGrane admits. “But all of this work is building up to our basic understanding of what it means to be a cat.”

[Bullish]

I had a great cat. He preferred Tuna over all other wet cat food. Unfortunately, the coyotes around here preferred cat.

[algore]

“When was the last time you saw one in the desert?”

I saw on licking my ice cream cone just the other day.

desert, dessert? I never was good at speling whatever

[Fungi]

How doesthat prove they “evolved?”

[drwoof]

You Done Good by the gatos!

[rlmorel]

I just caught this this 44 inch Striped Bass the other day:

I had to throw this one back (it was too big, you can only keep it for eating if it is between 29 inches and 31 inches long). But we did catch one last week on that charter we could keep and bring home to eat.

When I was cleaning the filets, I like to take off the dark colored meat, I think it tastes fishy. So I gave the stuff I removed to my cats, and they enthusiastically chowed it down.

I caught some Pollak and Haddock recently and gave the trimmings to my cats, and one was indifferent but unenthusiastically ate it, while the other one turned up his nose at it!

I guess they have standards-they only like the good stuff like the Striper!

[Ouderkirk]

Both of my cats presently refuse to eat fish of any kind. It’s really odd. My previous cats would nearly tear you arm off once the can was opened.

[oldvirginian]

😜

[Don W]

So, all I need to do is coat my fussy cat’s food with MSG and he’ll eat! Eureka! My world is SAVED!

[Don W]

They may be averse to water, but I had a cat that used to go fishing in the fish tank I had. She left the goldfish and other species alone. EXCEPT for the Plecostomus. She ate at least five of them until I put a cover over the tank she couldn’t dislodge.

[Jonty30]

I think it depends on what they grew up with.

[logi_cal869]

My neighbor’s cat loves mouse heads.

Headless carcasses are all that are left.

Umami. /s

[Salamander]

My dad gave me a bag of fresh deer legs for my mixed pack of Dobermans and Ibizan Hounds.

Things went from sweet gentle puppers to bloody call of the wild in 20 seconds flat.

Had a helluva time getting the deer legs away from them before werewolf mode kicked in.

Geeze.

[Celtic Conservative]

So you lost that argument and now you’re pivoting? I said quite specifically leaving the question of evolution out, cats are indigenous to Africa. And since your reading comprehension is abysmally low, I bid you goodnight.

CC

[jmacusa]

EWWWWW!

[Libloather]

I think it tastes fishy.

Isn't that the whole point of catching - fish?

[COBOL2Java]

My cat’s on steroid pills (prednisolone) for his digestive issues. It has a terrible taste. The vet suggested I crush the pill and stir it into something that has a strong umami scent. I tried tuna, and it works. He eats it all up.

[COBOL2Java]

Smells like Cankles?

"Smells like Cankles? What are you, nuts?"

[rlmorel]

One would think...but as I have aged, my tastes have changed. I no longer enjoy fish except for a few types...I still enjoy Cod, Striper, and Halibut, but I have no appetite for other types of fish.

When I was cleaning the striper filets, I was gratified to notice that they had no smell to them...what turns me off is either a fishy smell or fishy taste...I only eat white fish now, and only certain kinds. I can’t eat salmon, but I was never a fan anyway.

[mewzilla]

Our current feline overlord likes fish.

He likes poultry.

Likes beef.

But you don’t want to let him anywhere near bacon.

He really, really loves bacon.

Go figure.

[mewzilla]

Here's a link to the study...

Umami taste perception and preferences of the domestic cat (Felis catus), an obligate carnivore

Doesn't look like the eggheads were spending their own money, but it's from the UK, so hopefully it wasn't ours.