by Dr. Lisa Pierson

Just as with humans, diet comprises the bricks and mortar of health for our pets. Unfortunately, as we have strayed from a healthy diet, so have the feline friends that are dependent upon us for their food.

Often ignored principles of proper feline nutrition explain why cats have a better chance at optimal health if they are fed canned food instead of dry nuggets or kibble. Putting a little thought into what we feed our cats can pay big dividends over their lifetime and likely help them avoid experiencing serious, painful and costly illnesses. To begin, it is vital to understand that cats are obligate (strict) carnivores, and are very different from dogs in their nutritional requirements. Cats are designed to have their nutritional needs met by the consumption of a large amount of animal proteins (meat/organs), instead of those found in plants (grains/vegetables). Plant proteins are less complete than meat proteins.

A wild cat’s diet typically consists of rodents, birds, rabbits, lizards and insects. Such natural feline prey are high in animal protein, high in water content (about 70 percent) and low in carbohydrates (less than 5 percent). Most canned foods are of similar proportions.

Now, consider three key negative issues associated with dry cat food: 1) as a protein source, it’s too high in plant (grain or vegetable) protein and too low in animal protein; 2) the water content is far too low, at just 5 to 10 percent; and 3) its carbohydrate load is too high, as much as 50 percent. This is not what is needed to support a healthy animal.

Protein Puzzle

Humans and dogs can take the amino acids provided in plant proteins and, from those, produce any missing amino acids normally provided by animal proteins. Cats cannot do this, and so cannot live on a vegetarian diet.

That is why the protein in dry cat food, which is often heavily grain-based, is not equal in quality to the protein in canned cat food, which is meat-based. The protein in dry food, therefore, earns a lower score in terms of biological value. Many pet food companies use grain proteins, such as corn, wheat, soy and rice, which are cheaper ingredients than meat proteins, because this practice contributes to a higher profit margin.

Water for Life

Water, too, is vital to life and it also plays a critical role in the health of a cat’s urinary tract. Cats, by nature, have an extraordinarily low thirst drive and are designed to obtain water as part of their food. People who feed their cat dry food think that the animal is consuming enough water, because they see it drinking from a water bowl, but cats do not make up their water deficit this way.

We can think of wet food, packaged in cans or pouches, which is a minimum of 75 percent water (approximating that of a cat’s normal prey), as working to flush out the cat’s internal plumbing several times each day, because such a water-rich diet produces much more urine than a water-depleted dry diet. The fact that urinary tract problems are common in cats, and often life-threatening, underscores the importance of keeping water flowing through the kidneys and bladder, which is critical to the health of this organ system.

Carb Load

The high carbohydrate load of dry cat food wreaks havoc on the blood sugar balance of many cats because they lack the necessary enzyme systems to efficiently process carbohydrates. This comes as no surprise, given a cat’s strict carnivore status. While some cats are able to handle elevations in blood sugar levels, many are not, and this can contribute to the development of diabetes.

In the 20th century, dry kitten and cat food attracted a huge following due to its convenience and affordability, but informed and caring owners now realize that wet cat food is a far more healthy choice. Veterinarians and enlightened consumers understand that a core principle of nutrition is: pay more for good food now or pay the doctor later. This principle applies to our pets, as well as to us.

Finally, no discussion of dry versus canned food would be complete without addressing the myth that dry food is good for a cat’s teeth. In fact, this old tale has no basis in reality.

Lisa Pierson is a doctor of veterinary medicine based in Lomita, CA. For more information on how to make the switch to a healthier diet, see the “Transitioning Dry Food Addicts to Canned Food” at CatInfo.org.