Cats' Diet For the Last 24.999 Million Years

Dr. Brown asks us, perhaps while we're looking at kitty waiting at her food bowl, to take a step back and consider from whence kitty came. 5000 years ago, when the Egyptians worshipped her for her grace, beauty, and ability to control the rodent population, she hunted her food. She waited, she pounced, she missed. She did this several times. Eventually, using her keen eyes, superior quickness, sharp claws, and lethal fangs, she caught her prey and secured a meal. She repeated this sequence a few times each day.

The Importance of Wet Food

A mouse—wild cats' favorite prey—is analogous to today's "wet food." The portion of the animal that kitty's ancestors ate is 75 or 80 percent water, the same as what's in a can of modern cat food. Dr. Brown points out that it is through their food that cats in the wild get most of their moisture; cats are not naturally voracious drinkers. On a mostly dry food diet, a cat's thirst mechanism, the signal from her brain that says "you're thirsty, you need to drink," may not compel her to take in enough water to compensate for the lack of moisture in her diet. Among other risks, if kitty's body has insufficient water -— and since water dilutes and flushes out substances — solids such as crystals may more readily concentrate and turn into stones that produce pain or interfere with kitty's urinary system; if the stones are big enough they can prevent kitty from eliminating toxins, which is a life-threatening situation.

Therefore Dr. Brown recommends daily wet food for cats. If for some reason your cat refuses to eat wet food, and you've tried different brands and varieties, consider buying a kitty water fountain. The moving water typically incentivizes cats to drink out of them. Perhaps this is because in nature, moving water is clean water; perhaps cats are just fascinated by the movement and the "there, yet not there" aspect of the water; perhaps the running water tastes fresher.

Teeth

"But don't cats need to chew on dry food to clean their teeth?" you might be thinking. The idea is that as kitty chews, the abrasive action of the food scrapes away deposited matter that could lead to inflammation and erosion of the teeth and gums. But according to Dr. Brown, with the exception of specially formulated dental diets, studies have not shown any difference in dental health between cats on predominantly dry food diets and cats on predominantly wet food diets.

For one thing, cats barely chew. When kitty grabs a piece of kibble with his teeth, he crunches maybe once or twice, then it's down the hatch. Humans' saliva contains an enzyme that breaks down food as we chew it, so our digestive process starts in the mouth. However, cats' saliva does not have this sort of enzyme, so they get far less benefit from chewing; from their digestive system's point of view, it makes sense to get that food out of the mouth and into the esophagus, so the cats' body can start the process of extracting nutrients from it.

Carbs

Dr. Brown also notes that hard cat food tends to be higher in carbohydrates, which can be a bad thing for cats' dental health as well as general health. Compared to humans, cats have a low threshold for carbohydrates.

Humans have enzymes that help them effectively handle diets with a high percentage of complex carbohydrates — the American Heart Association recommends that humans get 50-55 percent of their calories from carbohydrates (the "good" carbs, like fruits, vegetables, and whole grains), and in some healthy people's diets, that figure is as high as 80 percent. But carbohydrates in those amounts would overwhelm a cat. The primary source of carbohydrates for cats throughout their evolution has been the small amount of digested vegetable matter in the stomachs of their prey.

Small carbohydrate-rich crumbs may break off from pieces of kibble, lodge between the teeth, and break down into starch and acid, thereby accelerating tooth and gum deterioration in cats.

Determining Carbohydrate Percentage on a Dry Matter Basis

"Dry matter basis" is simply the non-moisture part of the food. On that basis, wet foods tend to have a low percentage of carbohydrates—20 percent or less—whereas it is common for dry food to be comprised of 50 percent or more carbohydrates. This page -- http://www.thepetcenter.com/imtop/dm.html -- shows you how to compute carbohydrate percentages of cat foods on a dry matter basis.

Convenience of Dry Food

For most cats, there is no need to feed them dry food. (Exceptions may include cats who for some reason won't touch wet food or cats on a prescription diet.) However, regardless of the downsides of dry food, we have to admit: It's convenient. Almost everyone feeds their cat some dry food. In upcoming articles, we'll discuss ways to balance convenience and optimal nutrition.