Calories, Carbs, and Ingredients in Grain-Free Diets

In June, the Journal of Feline Medicine and Surgery published a study from the Cummings Veterinary Medical Center at Tufts University comparing grain-free and regular commercial cat food diets. The study looked at 42 diets that contain grains and 35 that are grain-free, comparing the calorie and carbohydrate contents.

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On average, the grain-free diets were lower in carbohydrates than the diets that contained grain, but there was a wide range in carb content across all of the foods. This means that if your cat needs a diet with fewer carbs, choosing a grain-free diet does not guarantee that the carbohydrate content will be lower than the food you are currently feeding. You need to actually compare the nutritional information on the labels and consult with your veterinarian to determine which food is the best option for your cat.

As far as calories go, the study found no significant difference between diets with grains and those without. Once again, reading the nutritional information on the label is the best way to determine a cat food’s caloric content.

There were some different trends in ingredients between the two food categories. Grain-free diets commonly included peas, cranberries, potatoes, and carrots, and were more likely to include venison, bison, or rabbit than diets with grains. Diets with grains commonly included rice, flax, cranberries, and oats. Poultry, egg, and fish were the most common animal-sourced ingredients across both categories, and one of the supposedly grain-free diets contained barley (oops!).

The truth about grain-free diets.According to Cailin R. Heinz, VMD, MS, DACVN, one of the authors of the study, ‘Grain-free’ is a marketing term rather than a health term. There are no data that show that these diets have any health benefits for dogs and cats over more traditional diets.” Most cats with food allergies are actually allergic to the protein source in their food, such as chicken or fish.

Joseph J. Wakshlag, DVM, Ph.D., Section Chief of Clinical Nutrition at Cornell University, has similar views, saying that grains are, “an energy source for cats to help keep foods affordable for everyone.” If designing his own cat food, Dr. Wakshlag would include lentils and pseudo grains, like quinoa. “I think they have more consumer appeal, which is the only reason I would not include certain grains, such as wheat, corn, or rice. Actually, I really like rice due to its digestibility.”

The bottom line. Grain-free diets are probably here to stay due to their widespread popularity, but don’t rely on that designation to tell you if a cat food is high-quality or not. Protein is the most important part of any cat diet, because cats are obligate carnivores and require meats to provide them with adequate nutrition. Even if we are someday able to determine the best carbohydrate source for cats, it will never replace their need for animal protein. Remember that:

  • The average grain-free diet contains less carbohydrates than the average diet containing grains, but carbohydrate content varies widely
  • Diets with and without grains commonly have similar caloric density
  • Grains and other carbs are an energy source for your cat

For more information and a link to the study, go to

Ever wonder if your cat eats better than you?

These are some of the ingredients found in cat foods today:

  • Apricot
  • Artichoke
  • Avocado
  • Bison
  • Blackberries
  • Chia
  • Lettuce
  • Papaya
  • Watercress
  • Zucchini