Ask a Vet: Is There an Ideal Diet for Cats?


I recently read Nina Teicholz’s The Big Fat Surprise: Why Butter, Meat, and Cheese Belong in a Healthy Diet. I had hoped the book would make me feel better about eating tasty things like bacon and cream, and indeed it did. But the book’s impact on me went beyond my feelings about my diet. It led me to reconsider much of what I know — and what the world knows — about nutrition.

I have stated many times that nutrition is chemistry. I stand by that. Nutrition is the study of nutrients (which are chemicals) in the body. Nutrition can be boiled down to biochemistry (a subset of chemistry) and physiology (which, in turn, is really complicated chemistry).

The bodies of mammals such as humans and cats are staggeringly complex things. It should come as no surprise that our physiologies are sufficiently complicated to be relatively poorly understood.

The Big Fat Surprise is about human nutrition. It challenges the belief — held almost as gospel by many — that dietary cholesterol and saturated fats cause heart disease. It’s a 300-page book, and I won’t go into all of its conclusions here. But I will give you my big conclusion from the book: The field of nutrition science is in its nascency. We have a lot to learn about human nutrition.

What does this have to do with cats? The book has gotten me thinking about our feline companions. Their bodies are no less complex than ours. We have a great deal of knowledge about how they work, but there is still a great deal that is not understood.

This is important because most caring cat owners want to feed their pets the best possible diet. For some, in fact, it is an outright obsession. The question then becomes this: What is the ideal diet for cats? Is there even such a thing as an ideal diet for cats?

Today on Dogster I spoke of the great flexibility of canine and human bodies. Humans, it turns out, can be very healthy eating low fat diets, higher fat diets, and all sorts of diets in between. We are omnivores who can tolerate great dietary flexibility. This is because our bodies are able to synthesize much of what we need from a variety of nutrients. We can turn protein into sugar or fat. We can turn sugar into protein and, as most people know, fat.

There are people and dogs thriving on all sorts of different diets. I know many perfectly healthy dogs who eat different diets. I know healthy dogs who eat commercial diets. I know healthy ones who eat homemade diets. There are healthy dogs who eat grain-free, or raw.

What about cats? We all know that cats are survivors, and indeed their bodies are very flexible. They, like us, have metabolic pathways for interconverting most of the nutrients that they need (although they do have more limitations, and therefore they have more so-called essential nutrients, such as taurine).

This flexibility has been of great use to cats fed commercial cat foods. Most of these foods are relatively high in carbohydrates. Cats are able to convert those carbs into other nutrients.

But there is a rub. Dogs and humans are omnivores. Cats are not. They are carnivores. Carnivores eat animals, and animals generally contain only small quantities of carbohydrates.

Cats’ ability to metabolize carbohydrates likely is an evolutionary safety hatch; during hard times, cats may have to resort to eating high-carb foods to avoid starvation. But I consider it unlikely that they evolved to thrive permanently on high-carbohydrate diets.

I mentioned that plenty of dogs are perfectly healthy on commercial diets. I am sorry to say that commercial diets do not seem to be serving our feline friends, as a species, quite so well.

Several medical problems in cats appear to be linked to diet, and they have reached epidemic proportions. Obesity, diabetes mellitus, and feline idiopathic cystitis (FIC, formerly known as feline lower urinary tract disease, or FLUTD) are staggeringly common among house cats.

Can I state definitively that commercial cat foods, with all their carbs, are to blame? Absolutely not. I have no proof, but the circumstantial evidence is significant. With that said, it must be acknowledged that many other factors, such as stress, neutering and spaying, and genetics likely also play a role in the pathologies mentioned above.

So what is the ideal diet for a cat? The fact is that nobody knows. Nobody can prove anything. It would seem logical that a diet that mimics that which is consumed in the wild (which is to say, whole prey animals) would be best. But at this time there is no proof of that. And remember that cats in the wild generally live only a couple of years; house cats, who for the most part are fed high-carb commercial foods, live up to 10 times longer.

For cats, as with humans and dogs, there may not truly be an ideal diet. Relative to us, cats are not as tolerant of dietary diversity. However, that doesn’t mean they tolerate no dietary diversity whatsoever.

I believe, but cannot prove, that over time our understanding of feline nutrition will evolve, and I think it’s likely that commercial diets will change as that happens.

But, speaking of evolution, remember that it is always happening. Natural selection applies to cats fed commercial diets, and eventually cats’ physiology may change to become far more carbohydrate tolerant — or even carbohydrate dependent.

What do you feed your cat? Let us know in the comments!

Read more on feeding your cat:

Learn how to live a better life with your cat on Catster:

Other stories by Dr. Eric Barchas:

Got a question for Dr. Barchas? Ask our vet in the comments below and your topic might be featured in an upcoming column. (Note that if you have an emergency situation, please see your own vet immediately!)

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