What Is a Limited Ingredient Cat Food?

Jamie Lovejoy, DVM
By Jamie Lovejoy, DVM on Jan. 18, 2021

As a modern cat owner, you’ve probably heard of a “limited ingredient” cat food. Perhaps your veterinarian has recommended one of these diets to treat your cat’s food allergies, or maybe you saw a grain-free limited ingredient diet advertised as the most natural option for your cat.

However, before these foods end up in your cat’s bowl, it’s important to know what these diets entail, which cats they can truly benefit, and how to choose a product that works the way you and your veterinarian want it to.

What Does “Limited Ingredient Cat Food” Mean?

In theory, a limited ingredient cat food diet is exactly as it sounds: a diet with fewer ingredients. The goal is to limit the number of protein and carbohydrate sources while maintaining a nutritious diet, usually to avoid adverse food reactions or food allergies.

However, the term “limited ingredient” is not regulated by the FDA. That means that pet food companies can write “limited ingredient” on the label of any cat food, no matter how many ingredients there are.

If you want to make sure you are feeding a limited ingredient diet, you will have to look at the pet food label and the ingredient list and compare it to some other ingredient lists, or better yet, ask your veterinarian to take a look. 

What Is in a Limited Ingredient Cat Food?

A truly limited ingredient cat food will have the following ingredients and little else:

  • One protein source
  • One carbohydrate source
  • Supplements
  • Fats to balance the nutrition

Cats are obligate carnivores, meaning they must eat meat, so it is very important that the protein source be of animal origin. In limited ingredient diets, the animal protein is usually a “novel protein,” or one that your cat probably has not been exposed to before.

Common veterinary-recommended protein sources in limited ingredient diets include:

  • Duck
  • Rabbit
  • Venison 

Carbohydrate sources that are often used in limited ingredient diets include potatoes and peas.

Fruits, additional vegetables, and additives such as kelp should be generally avoided in a diet made for treating food allergies, as they can interfere with determining a cat’s response to the protein source.

Is a Grain-Free Diet a Limited Ingredient Cat Food?

Although grain-free cat food diets may have ingredient restrictions, they are not considered by veterinarians to be limited ingredient diets.

The term “grain-free” is not regulated by the FDA and is used more for marketing than to indicate food content or quality. It also says nothing about the number of ingredients used. These diets generally swap out whole grains for other carbohydrate sources such as lentils, peas, and sweet potatoes, but they have very similar protein sources to other cat foods (poultry, egg, and fish).

There is still no evidence to suggest that grains are harmful to cats (grain allergies are exceedingly rare), and most cats digest them very well. That said, there are grain-free, limited ingredient diets whose carbohydrate sources are not grain based if you and your veterinarian decide that is best for your cat.

Is Limited Ingredient Cat Food Better?

If your cat is healthy, there is no reason to try to switch to a limited ingredient diet because you think that it might be “better” for them. The nutrients in your cat’s food are much more important than the ingredients that provide them.

A well-balanced diet made from chicken, beef, eggs, and rice is likely better than a limited ingredient cat food that is poorly balanced but made from a novel protein.

Does My Cat Need a Limited Ingredient Food?

The most common reason for a cat owner to seek out a limited ingredient diet is to try to diagnose and/or treat a food allergy.

Symptoms that may be linked to allergies include:

  • Vomiting

  • Diarrhea

  • Itchy skin

  • Frequent ear infections

But true food allergies are not as common as you may think. However, if your veterinarian does suspect a food allergy, they may recommend a diet trial with a limited ingredient diet. Limited ingredient diets may also be useful in the treatment of pancreatitis and inflammatory bowel disease.

If you wanted to switch because you thought that maybe a limited ingredient diet could prevent a food allergy from developing in the first place, it would actually do more harm than good. Exposing your cat to exotic proteins such as venison, kangaroo, and duck may even make it harder to treat a real allergy (in the unlikely event that one develops), as those novel protein options will no longer be available to you for a diet trial.

Using LID Cat Food to Test for Food Allergies

High-quality limited ingredient diets are readily available, but due to issues with contamination control in store-brand limited ingredient diets, most veterinarians exclusively recommend a prescription hydrolyzed protein diet for food allergy testing. Prescription pet food companies like Royal Canin have stringent quality control, even going as far as PCR testing for contaminant proteins.

In prescription hydrolyzed diets, the protein molecules are broken down into microscopic pieces that the body can use and digest but not recognize as a potential allergen. If your cat has been exposed to many different protein sources, this type of diet may take the guesswork out of a diet trial.

If you think your cat may benefit from a novel-protein, limited ingredient diet, be sure to ask your veterinarian about your options. They can work with you to determine the best brand and protein source based on your cat’s dietary history.

Featured image: iStock.com/pat138241

Jamie Lovejoy, DVM


Jamie Lovejoy, DVM


Dr. Jamie Lovejoy graduated from Tufts Cummings School of Veterinary Medicine in 2012 after an undergraduate degree in Marine Biology. ...

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