Sugars, spices, and all the beautiful things we know are of no importance to cats. Our feline friends only care about one type of food: meat. Moreover, this trend does not stem solely from the little killer inside it who lurks a bird to catch it or a mouse to torture him; it is also because cats cannot taste sweets.

Scientists have been able to trace the cause to a gene. The tongues of most mammals contain taste receptors - proteins on the cellular surface that bind to food, which activates intracellular processes and ends up sending a signal to the brain. Humans have at least five types of tasting buds in the tongue so that they can eat sour, bitter, salty, sweet, and meaty taste (and possibly fat as well). The dessert receptor consists of a pair of protein proteins that are produced by two separate genes: Tas1r2 and Tas1r3.

All cats - including lions, tigers, and even a beautiful long-haired British cat - lack a piece of DNA found in the Tas1r2 gene in other mammals. As a result, this incomplete gene in Felidae (the so-called "false gene" may be more appropriate) does not consequently produce the proper protein and thus deprive the cats to taste sweets. "Cats do not taste sweets the way we do," says Brand, a neuroscientist, the former co-director of the Monel Senses Center in Philadelphia, and an honorary member of the center.

Brand and his colleague Xia Li discovered a pseudo-gene for nearly twelve years, studying and adding to decades of historical evidence about cats' inability to taste sweets, as they have shown no preference for sweetened water over plain water.

Of course, there are a lot of historical notes pointing in the other direction; there are cats eating ice cream, or enjoying candy floss, or seeking marshmallows. "Maybe some cats can use the Tas1r3 gene receptor to taste high concentrations of sugars, or maybe they seek another compound that we do not know," says Brand.

However, scientists naturally know that cats can taste things that we humans cannot eat, such as adenine phosphate, the compound that supplies all living cells with energy. "There is nothing specific to meat but to refer to meat," says Brand. Xian Li says many other animals have a different set of receptors, from chicken that also lacks a candy-tasting gene, to catfish that can taste water-based amino acids in nanomolar concentrations. "Their receptors are more sensitive than the concentration of the surrounding materials, and catfish that first discover rotting food have a higher chance of survival," explains Brand.

Moreover, cats are not the only animals in this. Brand and his colleagues have found that all felines (about thirty-six species) and many other types of carnivorous mammals only lack candy-tasting receptors. Cats may also require different ingredients to enjoy (and digest) sugars, such as glucose in their livers, an essential enzyme that controls carbohydrate metabolism and prevents glucose from sweeping the blood of an animal.

Although cats are unable to handle sugars, most major cat food manufacturers use rice or other grains as a component of their diet. "This may be an explanation for a cat's diabetes," says Brand. "Today's cat food contains up to 20% carbohydrates, which cats are not accustomed to and cannot deal with."

Well, it might be painful for these predators who live among us not to taste sweets, but it also means cat lovers do not have to worry about their cats snatching the candy bars they leave unattended.