Study Results Can Sometimes Be Misleading

Cat Food

Story at-a-glance -

  • A recent study presumably designed to determine if carnivorous kitties truly benefit from high-protein diets seems to indicate kittens fed dry food diets with only moderate levels of protein plus carbohydrates have more beneficial gut bacteria.
  • As soon as the study was published, headlines appeared around the Internet suggesting “High-protein diet may be unhealthy for kittens.”
  • The study involved feeding biologically inappropriate dry food to kittens and then measuring their levels of certain GI bacteria. Kittens fed the dry formula with lower protein content and moderate amounts of carbohydrates had higher levels of certain friendly bacteria than kittens fed the high-protein/low carb dry food.
  • Questions to ask before taking these study results seriously: Do we know what levels of beneficial gut bacteria are normal for kittens, or what good-to-bad bacteria ratio is ideal? Also, what impact does biologically inappropriate processed kibble have on gut bacteria?
  • The goal in nourishing your kitty should be to provide a diet that closely replicates his natural diet, and adding beneficial supplements to fill in any nutritional gaps.

By Dr. Becker

A recent study1 conducted by researchers at the University of Illinois and published in the British Journal of Nutrition set out to determine whether cats, as obligate (strict) carnivores, are healthiest when fed high-protein diets.

“There are a lot of diets now, all natural, that have high protein and fat and not much dietary fiber or carbohydrates,” said one of the researchers, Kelly Swanson of the University of Illinois Department of Animal Sciences.

University of Illinois Study

For the study, participants (kittens) were fed either a high-protein, low-carbohydrate (HPLC) diet or a moderate-protein, moderate-carbohydrate (MPMC) diet.

To determine the health of their study subjects, the researchers decided to use gut bacteria as a measure. In terms of healthy bacteria counts, study results revealed that:

  • As expected, kittens on the HPLC diet had higher levels of proteolytic bacteria that break down protein.
  • Also as expected, the kittens on the MPMC diet had higher levels of saccharolytic bacteria that break down carbohydrates.
  • The kittens fed the MPMC diet had higher levels of bifidobacteria, which is linked to higher blood ghrelin levels. Ghrelin is a hormone that acts as an appetite stimulant and may be linked to weight gain. Bifidobacteria may support GI health, since low levels in humans are linked to inflammatory bowel disease.
  • The MPMC kittens also had higher levels of lactobacilli, a bacteria linked to gut health and healthy cholesterol and leptin levels. Blood leptin levels signal the body to stop eating and are thought to play a role in cholesterol metabolism, appetite and body weight regulation.

Although kittens fed the high protein-low carb diet had lower levels of certain friendly bacteria, all the animals remained in good health throughout the study.

Media Interprets Study Results

As soon as the University of Illinois study was published, online media outlets picked it up and ran articles with headlines like: “High-protein diet may be unhealthy for kittens,” and “High-protein diet not so good for kitty's belly. Kittens fed a high protein diet have less beneficial gut bacteria than those who eat a more balanced diet.2

So a “more balanced diet,” according to the headline, is one with only moderate amounts of protein plus moderate amounts of carbohydrates. More balanced for what species, I have to ask? Balanced for an omnivore, perhaps … but certainly not for an obligate carnivore!

Hopefully any cat owner who runs across that headline will read the entire article before deciding to cut back on the protein in their pet’s diet.

Factors That May Have Impacted Study Results

The biggest factor to consider is that the two diets used in the study were, unfortunately, dry food formulas, which means they were seriously deficient in a nutrient felines MUST get from their diet -- moisture. We also know most dry pet foods are cooked twice: once when the protein is rendered (turned into meal), and a second time when the kibbled mixture is extruded to form small, crunchy nuggets. This extreme processing also changes the structure of proteins and destroys vitamin A, vitamin E and the B-group vitamins, at a minimum.

Next we have to wonder about the protein source used in the dry food diets. It was unnamed in the study abstract, so we don’t know whether the food contained animal protein, a less biologically appropriate protein (for example, from a plant), or a combination. Generally speaking, dry pet food made with animal protein contains rendered meat by-products, which are more difficult for pets to digest than human grade meat.

Lastly, we don’t know what exactly constitutes ideal numbers of friendly gut bacteria in kittens. Generally when we look at GI bacteria issues, we look at the balance of good-to-bad bugs. Quantifying that a kitten has a certain number of this or that bacteria may only be relevant to overall GI flora health and species. So the fact that the study kittens eating the higher protein food had lower levels of certain species of friendly bacteria isn’t particularly significant, in my opinion.

The Best Diet for Cats is Moisture-Rich, Fresh, Balanced, and Species-Appropriate

The University of Illinois study frustrates me because many people won’t look at the above issues when reviewing the study’s outcome. Additionally, it’s a good example of the media achieving their goal of creating a fear-based uproar among pet owners. At a time when evidence in favor of real meat, moisture-rich diets for cats is finally getting the attention it deserves in both the veterinary community and among an increasing number of pet owners, up pops a study like this one that seems to encourage feeding carb-laden dry kibble to cats.

If the kittens in the study had been fed real, fresh animal protein with and without the addition of carbohydrates, in my opinion, gut bacteria results might be more meaningful.

As most of my regular readers know, I’m passionate about feeding fresh, living foods to healthy dogs and cats. The goal in nourishing your kitty should be to provide a diet that closely replicates his natural diet, and adding beneficial supplements to fill any nutritional gaps.

If you’re feeding dry food and concerned about your kitty’s gut bacteria balance, I recommend you talk with your holistic vet about your pet’s diet and any supplements and medications you’re giving him. There are a number of ways friendly GI bacteria can be compromised, and often a high quality pet probiotic can be very beneficial. For more information, I recommend reading Your Pet's Good Health Begins in the Gut