By Dr. Becker
Even if your own cat is a hearty eater, I'm sure you're aware that many feline companions are notoriously persnickety at mealtime.
For better or worse, the results of a recent study1 by scientists at the Monell Chemical Senses Center in Philadelphia may shed some light on why little Percy or Priscilla is so darned fussy about food.
Cats (Meat-Eaters) and Plant-Eating Animals Have Certain Taste Receptors in Common
Cats are obligate carnivores, meaning they must eat meat to survive. Their bodies aren't designed to process or assimilate large amounts of plant-based nutrition. But as it turns out, despite their strict meat-eating nature, felines have certain significant genes in common with plant-eating herbivores.
The specific genes I'm talking about give herbivores the ability to taste bitter flavors, which helps them avoid eating poisonous plants. Animals use their tastebuds to identify certain characteristics of foods they're about to ingest.
Sweet flavors mean there's sugar in the food, which is an important source of energy. And it has long been assumed by scientists that a bitter taste warns vegetarian animals that a plant or unripe fruit contains a harmful substance.
Cats have no sweet taste receptors, probably because as strict meat-eaters, they evolved without those receptors since they had no use for them. Other exclusively carnivorous animals, e.g., sea lions and spotted hyenas, have also lost the ability to taste sweet flavors.2
Cats (Carnivores) Are Equipped with Several Bitter Taste Receptors That Detect Toxins in Plants. The Question Is, Why?
Animals' taste buds evolve in response to changing dietary requirements. Over time, alterations in an animal's normal diet can eliminate the need to sense certain chemicals in food, which causes the genes to mutate in response.
A good example of this is cats, which as strict meat-eaters have evolved without the ability to taste sweet flavors. But here's a question: If the ability to taste bitterness is nature's way of alerting vegetarian animals to potentially toxic plants, why do strictly meat-eating cats have a need to taste bitter flavors?
In theory, if cats have evolved with no ability to taste bitterness, their receptor genes should be mutated accordingly. However, when the Monell scientists looked at the genomes of different carnivorous species, they learned they all possess a similar amount of genes for bitter taste.
For example, cats have 12 identified bitter taste receptors, polar bears have 13, ferrets have 14, dogs have 15, and the giant panda has 16. All these animals belong to the order Carnivora, however, in terms of their diets, they range from strictly carnivorous (cats) to exclusively vegetarian (giant panda).
So the question becomes: If primarily meat-eating animals aren't likely to sample any bitter or potentially toxic plant-based food sources, why are they genetically equipped to taste bitter flavors?
Cats' Bitter Taste Receptors May Help Them Detect Toxic Compounds in Their Prey
Lead study author and molecular biologist Peihua Jiang set out to evaluate feline taste buds. He did this in the laboratory by inserting the cat taste receptor gene into human tissue cells. Together, the cells and the gene behave as a taste receptor that responds to chemicals.
The taste receptor created by Jiang responded to bitter substances in toxic plants, as well as to substances that also activate human bitter taste receptors.
The researchers determined feline bitter taste receptors help them detect potential toxins in the prey they hunt in the wild, including frogs and toads. According to study author Gary Beauchamp, Ph.D., a behavioral biologist at Monell:
" … [B]itter taste could exist to minimize intake of toxic compounds from skin and other components of certain prey species, such as invertebrates, reptiles and amphibians." 3
Could Bitter Taste Receptors Help Detect Infections in Cats?
The researchers suggest that cats aren't exposed often enough to bitter and toxic meat-based foods to warrant the number of bitter taste receptors they have retained.
Therefore, the study authors conclude that cat taste receptors may have evolved for reasons other than taste. Interestingly, human bitter taste receptors are found not only in the mouth, but in the heart and lungs as well, and may serve to detect infections.
"Alternate physiological roles for bitter receptors may be an important driving force molding bitter receptor number and function," says Beauchamp.
"For example, recent Monell-related findings show that bitter receptors also are involved in protecting us against internal toxins, including bacteria related to respiratory diseases."4
Whether this is also the case with kitties remains to be seen.
Based on this new discovery that our feline companions have taste buds for bitter flavors, it could be they pick up subtle noxious tastes in the food we offer them.
This would explain why many cats are so food finicky … except that dogs have a similar number of bitter taste receptors and most have never met a meal they didn't like.
Perhaps cats are simply more sensitive to bitter substances than dogs, or are able to detect many more bitter compounds in their food than dogs are. It's possible ingredients that are essentially tasteless to your dog taste just plain nasty to your cat … which would certainly explain why so many kitties are so selective when it comes to the food they will eat.
Tips for Encouraging a Fussy Cat to Eat
My first recommendation is to try to slowly and safely transition a cat eating processed pet food to a balanced, fresh, organic, non-GMO, species-appropriate diet. Unless your cat is hopelessly addicted to the processed stuff, offering fresh whole food with no additives or preservatives essentially eliminates the possibility her delicate tastebuds will detect noxious chemical compounds in her meal.
Whether her diet is fresh or processed, however, the goal should always be to make sure your cat eats something. Unlike dogs and humans, it's dangerous for kitties to go any length of time without nourishment, as it can lead to a potentially fatal liver disease called hepatic lipidosis.
Enticing a picky kitty to stay nourished can require creativity along with some gentle prodding, and lots of patience. Things you can do to tempt your finicky feline's sensitive tastebuds include:
- Warming her food to bring out the aroma
- Offering canned food with a strong smell or topped with a sardine (packed in water)
- Offering new food from a paper plate in case she's developed an aversion to her food bowl for some reason
- Offering a small selection of different flavors and textures of canned cat food or home cooked meat or bone broth
- Enticing her with species-appropriate human food she has enjoyed in the past, such as warm baked chicken or salmon
- If she's addicted to dry food and refuses everything else, try adding warm water to each meal or add an aromatic enticement like tuna juice, warm goat's milk, or chicken broth
It's also important to make kitty's mealtime a very low-stress, pleasant experience. Make sure you feed her in a calm, quiet environment that is optimally comfortable.