How many times has your cat turned its nose up at the food you so lovingly provided? You have probably lost count, but researchers suggest that your cat's pickiness could be down to how their taste receptors respond to bitter compounds. The way domestic cats perceive bitter tastes is surprisingly unique compared to us, which could explain why they can be such fussy eaters. 

The researchers of the study, published in the journal BMC Neuroscience, identified two bitter taste receptors in domestic cats, known as Tas2r38 and Tas2r43, and studied how they respond to bitter compounds. They also used cell-based experiments to compare cat and human taste receptors.

The ability to taste bitter chemicals could have evolved as a form of protection against toxic compounds found in plants. While all cats, including wild tigers, don’t consume much plant material, they may still have to taste bitter compounds in their food and medicine.

Co-author Joseph Rucker, from Integral Molecular, said in a statement: “Feline bitter taste has not been well studied. We applied our experience in studying membrane proteins, such as taste receptors, to enable this first glimpse into how domestic cats perceive bitterness in food at a molecular level.”

Researchers found that the cat taste receptor—Tas2r38—was less sensitive to the bitter compound phenylthiocarbamide (PTC) and did not respond to the bitter compound 6-n-propylthiouracil (PROP), compared to equivalent human taste receptors.

“We were surprised to see that one of the cat taste receptors responded to a more limited range of bitter compounds compared to humans, suggesting that cats may be detecting a narrower, or at least a different, repertoire of bitter-tasting compounds,” Rucker said.

Tas2r43, the other cat taste receptor, was far more sensitive to the compound denatonium, which is often used to prevent children and pets from consuming chemicals such as antifreeze. They were, however, less sensitive to the bitter Aloe compound aloin. They were also insensitive to saccharin, an artificial sweetener that tends to have a bitter aftertaste for some people.  

“We confront the challenge of 'finicky cats' every day. As such, it is exciting to find an unexpected receptor response to bitter compounds that has never been described in the literature to date for any other species,” said co-author Nancy Rawson from AFB International, in a statement.

“These insights and future discoveries will be invaluable in formulating appealing food for cats, as well as enhancing the acceptability of their medications,” she added.