When I graduated vet school a decade ago, fiber was the trend du jour. Every dog diet wanted you to know about its fiber content. Now, the talk has turned to protein: “Let’s leave grain behind! Protein all the way!” I’m glad to see people focusing on the importance of protein, because it is important, but we also need to understand its place in the greater context of a dog’s overall diet. To review, there are three sources of energy in a food: carbohydrates, fats and protein. Dogs, like people, are omnivores. They are adapted to digest a wide variety of both meats and plant materials to obtain their fuel in an efficient manner. Protein is the basic building block of the body. When a dog ingests a piece of meat, the body breaks the protein down into its component, amino acids, which can then be reassembled into a huge assortment of vital molecules and tissues. Connective tissue, cell membranes, fur, skin, hormones, enzymes: All of these essential body components rely on protein.
And, of course, we can’t forget muscles. The amino acid components of muscle tissue are constantly being broken down, so adequate protein intake is vital to not only build muscle, but also maintain it. Without adequate protein intake, dogs may develop a dry coat, become anemic and eventually lose muscle mass as the body fights its deficiency. So how does this relate to pet food? Commercial dog foods vary widely in terms of their protein content, a reflection of the fact that different dogs have very different needs. The Association of American Feed Control Officials (AAFCO), an organization that sets nutritional guidelines for the pet food industry, recommends that protein make up a minimum of 18 percent of the dry weight of the food for adult dogs, and 22 percent for growing pups. If you read bag labels (and you should), you can see this number can vary from the 18 percent range up to 50 percent and higher. But it’s not only the amount of protein that matters; the quality of the protein matters too. Protein can be derived from animal sources, from grains, or from plant products (e.g., soybean meal and corn gluten meal). Animal-derived proteins (e.g., chicken, beef, lamb, fish, and even the oft-maligned byproducts) are generally considered the highest-quality sources of protein since those proteins are the most easily digested and absorbed.
And what happens if you give a dog excess protein? Usually, nothing. A healthy body can deal with excess protein and can store some of the components for energy. The current thinking regarding kidney disease indicates that phosphorous, more so than protein, is the driving dietary factor behind the progression of renal insufficiency. That being said, any dog with renal disease should be under the supervision of a veterinarian, as dietary needs vary with not only individuals, but also the same individual over time. There is no one-size-fits-all diet. Fortunately for us, there is a wide assortment of high-quality foods out there that can provide your dog with just the right protein it needs to thrive. If you need guidance to select a diet that’s appropriate for your favorite canine, don’t forget to consult with your veterinarian!