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How Carbs Can Severely Damage Your Cat's Health

In spite of what many conventional veterinarians and pet food makers claim, nature did not design felines to digest carbohydrates. They simply don't have the enzymes required to thoroughly break down grains and starches. Here's what can happen to your kitty when you feed her carb-containing food.

cats and carbohydrates


  • The ultraprocessed pet food industry is obsessed with convincing pet parents that cats aren’t carnivores and can therefore thrive on diets crammed full of carbohydrates
  • The scientific fact that cats are indeed true carnivores, coupled with a nutritional awakening among cat parents poses a problem for an industry that has made its fortune selling biologically inappropriate grain- and carb-based cat food
  • It’s simply a fact that cats’ bodies aren’t designed to digest carbohydrates efficiently, and most carbs in a cat's diet convert to sugar and fat — leading to obesity and related diseases
  • Unprocessed animal tissue is an essential and species-perfect source of protein, vitamins, and moisture for cats; no adequate substitute exists

Editor's Note: This article is a reprint. It was originally published November 16, 2021.

I recently noticed that a quite ridiculous study published in 2017 titled “Cats and Carbohydrates: The Carnivore Fantasy?”1 is making an encore appearance in pet food industry journals. The study was conducted by a university researcher in Canada and another in Belgium, and purports to explore how cats digest carbohydrates.

It’s curious that veterinary researchers would be involved in a study that suggests cats aren’t really carnivores, until you reach the end of the report and read, under the Conflicts of Interest section, that one of the two is the Royal Canin Veterinary Diets Endowed Chair in Canine and Feline Clinical Nutrition at the Ontario Veterinary College.

As many of my regular visitors here at Healthy Pets have learned, most veterinary colleges leave all their nutrition training and collaborative research in the hands of very large ultraprocessed pet food companies, in this case, Royal Canin (owned by candy bar giant, Mars).

Big Pet Food Is on a Mission to Prove Cats Aren’t Carnivores

In recent years, dog parents have become increasingly interested in ensuring they’re feeding their pets species-specific diets, and the pet food industry has responded by trying to convince the world dogs are omnivores or even vegans, not carnivores, and should be eating diets high in grains and starches.

Felines present an even greater problem for Big Pet Food, because as obligate carnivores, they have even less ability than dogs to digest carbs (and, like dogs, they have no nutritional requirement for them), and pet parents are catching on.

How is the ultraprocessed pet food industry supposed to continue to sell massive amounts of biologically inappropriate grain and carb-based diets to cat owners who are increasingly demanding diets designed for true carnivores? I guess one way is to push the idea that it’s a “fantasy” that cats require meat-based vs. plant-based diets, and then conduct studies with a predetermined outcome to offer as evidence.

The Focus Is on Ingredients Cats Don’t Need and Can’t Digest

Here’s an example of the “science” behind ultraprocessed cat food. This is from, referencing the “carnivore fantasy” study:

“Once cats do manage to digest carbohydrates, they can’t use the end products, such as glucose, as well as dogs do. Scientists found that uptake of the simple sugar, or monosaccharide, glucose took twice as long in cats as in dogs. Cats also seem to lack the ability to alter their uptake of digested carbs based on the quantity in their diet, which dogs are able to do.
However, the authors of the literature review noted that research is inconclusive on what concentration of sugars is needed to reach maximum uptake in cats’ intestines. That means scientists don’t know if the carb concentration in cat food is beyond or below what cats’ digestive systems can use.
One early study, from 1977, did find that cats could digest 40 to 100 percent of the starch in cat foods, depending on the carbohydrate source.”2

This is a rather disturbing example of just how focused processed pet food producers are on learning how much dogs and cats can tolerate of the biologically inappropriate ingredients in their formulas.

Anyone interested in the long-term health, longevity, and vitality of dogs and cats should be focused on offering the full range of dietary nutrients their bodies are designed to make the best use of — not how many inappropriate ingredients they can tolerate, and in what quantities.

Carbs Can Cause Massive Damage to a Cat’s Health

Felines aren’t designed by nature to digest large amounts of carbohydrates. And since domestic cats evolved to eat very low amounts of grains and starches, simple common sense tells us that a diet high in carbohydrates has the potential to create ill health (example: the feline obesity and diabetes epidemics that can be reversed by eliminating starch from the diet).

The activity of a cat's liver enzymes is designed to handle protein and fat as energy sources, not starches. Most of the carbs in a cat's diet are ultimately stored as fat. Cat macronutrient self-selection research shows cats choose diets with approximately 12% carbs; higher levels require the pancreas to produce more insulin and digestive enzymes to break them down.

Many cats end up with chronic pancreatitis, inflammatory bowel disease (IBD) and diabetes as a result of chronic dietary abuse from excessive starch they cannot metabolically manage.

Not surprisingly, you won’t find carbohydrate content listed on your bag of cat food because manufacturers choose to keep it a secret. Do this simple equation to find out how much sugar you’re feeding: add up the amount of protein, fat, moisture, and ash (estimate 6% if it’s not listed) and subtract from 100. That number is the percentage of carbs (sugar) found in your kitty’s food.

It’s easy to see why so many cats have chronic inflammatory and degenerative diseases — they’re being fed a very unnatural diet of refined carbs they were never meant to eat.

Research shows that cats fed diets high in simple sugars become hyperglycemic (the first symptom of insulin resistance). Most cats aren't attracted to sweet-tasting foods (unlike dogs and people), and instead prefer food that tastes like animal products. This is one of several clear indicators of the strict carnivorous nature of felines.

Unprocessed Animal Tissue Is Perfect Nutrition for Cats

Felines have a unique nutritional biochemistry that is significantly different from other animals. As obligate carnivores, they must consume animal tissue to meet their very specific nutritional requirements.

For example, kittens require 1.5 times the amount of protein as the young of other species, and adult cats need 2 to 3 times the amount other adult animals require. This is because omnivores and other mammals use most of the protein they consume not as a source of energy, but for growth and body maintenance.

Cats use protein for those purposes plus as a source of energy. When most animals are fed a low-protein diet, their bodies conserve amino acids to manage the deficit. But a cat's body must continue to use protein even when there's not enough in the diet, which is why protein malnutrition happens quickly in sick or injured cats, and those with anorexia.

In addition to their increased need for protein, cats also have a higher requirement for certain specific amino acids, such as taurine, found naturally in animal tissue. They also have a special requirement for vitamin A, which is available naturally only in animal tissue.

They lack the intestinal enzymes necessary to convert B-carotene in plants to the active form of vitamin A. Vitamin A is essential for maintenance of vision, growth of bone and muscle, reproduction, and the health of epithelial tissues. Vitamin D is also essential in the diets of cats because they lack the ability to synthesize it through their skin. The liver and fatty tissue of free-range animals is rich in vitamin D.

Domestic cats evolved from desert-dwelling ancestors, which is why they must get most of their water from the food they eat. Felines are not as responsive as other animals to sensations of thirst or dehydration. When fed a dry food diet, cats aren't driven to search for another source of water to make up the difference between what their bodies require and what their diet provides.

This results in chronic mild dehydration, a condition that will ultimately lead to disease, especially of the lower urinary tract and kidneys.

Cats and Carbohydrates: The Big Pet Food Fantasy

As always, it’s “buyer beware” when selecting commercially available cat foods. As hard as certain activist organizations and the pet food industry may try to convince you otherwise, dogs will remain scavenging carnivores and cats will remain obligate carnivores, and neither will evolve to require or efficiently digest highly refined, carbohydrate-laden diets.

Feed your cat a healthy variety of biologically appropriate foods by offering a combination of homemade raw (or cooked), commercially available balanced raw, dehydrated/freeze dried raw, and/or human grade canned. The diet you feed your feline family member should be nutritionally optimal, species-specific, and made from high-quality meat protein sources.

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