The Importance of Protein Quantity and Quality

Published: September 14, 2012
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When owners are picking out foods for their cats, they often focus on the quantity rather than the quality of individual nutrients like protein. I think there is a simple reason for this — information about how much of something a cat should be eating or how much is included in a particular food is everywhere. Take these two examples:

  1. The Association of American Feed Control Officials (AAFCO) Nutrient Requirements for Cats is essentially a long list of nutrients that have been deemed essential to good feline health and their minimum percentages that must be included in a food for it to be labeled as complete and balanced. AAFCO’s minimum protein level for feline adult maintenance is 26 percent.
  2. Every AAFCO-approved pet food label includes a guaranteed analysis that lists the maximum amount of moisture and fiber and the minimum amount of protein and fat that the product contains. You’ll see a wide range protein percentages on cat food labels, but I think that for most healthy adults, approximately one-third of the diet ideally should consist of protein.

That takes care of quantity, but what about quality? All proteins aren’t created equal.

There are two ways to think of quality: purity and importance. For instance, you could buy lentils that are organically grown, received the best of everything in the field, and were perfectly harvested and packaged. Those would be some high-quality lentils. Since lentils contain a lot of protein, do these "pure" lentils constitute a high-quality source of protein for cats? No, because lentils don’t contain the right balance of essential amino acids (the building blocks of protein that cats can’t make themselves) to promote health. Lentils can still be included in a feline diet to provide the building blocks for the amino acids that a cat’s body can manufacture, but alone they would not be a satisfactory source of protein.

Which brings us to "importance." Essential amino acids are very important. If a cat does not get adequate amounts of all of the essential amino acids in her diet, serious health consequences can quickly follow. In this way, animal-based protein sources are higher-quality than are plant-based. In other words, chicken, fish, eggs, etc., have a better balance of essential amino acids for cats than do plants. Again, this is not to say that plant-based protein sources have no role in cat foods, just that animal-based proteins must be included unless the diet is heavily supplemented with essential amino acids.

Owners need to make sure that not only do their cats get enough protein, but also that it is high-quality in both senses of the word. Animal-based sources of protein should appear at the top of the ingredient list (remember the ingredient list is written in order from the most to the least prevalent ingredients included in the food). Assessing purity is more difficult. This is where monitoring your cat’s response to a food comes in. Is her coat glossy? Are her stools firm? Does she not vomit? Is her energy level high for her age? If so, you’ve probably found a food that meets all the definitions of "high-quality."

Dr. Jennifer Coates

Image: Rob Byron / via Shutterstock