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Limited Ingredient Diets & Adverse Food Reactions

Drs. Foster & Smith Educational Staff
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Have you noticed that more and more dog and cat food formulas are calling themselves "Limited Ingredient?" Have you ever wondered why fewer ingredients might be beneficial to certain pets? Here's the science behind the pet food labels, and the difference between veterinary-approved diets and options you'll find from major pet food brands.

What is a Limited Ingredient Diet?

The traditional definition of a limited ingredient diet is one that contains a single protein source and a single carbohydrate source. For years, veterinarians have been recommending this type of diet when working with animals suspected of having food allergies.

The most common approach in finding an appropriate diet is to evaluate what the pet has eaten in the past. Specifically, what protein and carbohydrate sources were present in the diet(s) being fed. Most veterinarians will recommend feeding either a limited ingredient diet that contains a single, novel (new) protein source and a single, novel (new) carbohydrate source, or a hydrolyzed protein diet.

How it works

A novel protein/novel carbohydrate diet is simply one that contains proteins and carbohydrates that the pet has never been fed before. If an animal has never been fed a particular protein or carbohydrate before, the animal will not have an allergic reaction to the food because the animal's immune system has never been exposed to it before. Depending on what a pet has eaten in the past, examples of novel proteins might include venison, bison, elk, quail, rabbit, ostrich, kangaroo and wild boar. Examples of novel carbohydrates include peas, potatoes and oats. What might be new/novel to one pet might not be novel to another.

The last type of diet is the hydrolyzed protein diet. In these diets, the protein has been broken down into its component amino acids, making it much less likely for the animal's immune system to recognize and react to the protein.

How long is an LID fed?

If the common signs of food allergies (gastrointestinal discomfort and/or itchy ears and skin) start to decline on the new diet, a veterinarian may conclude that the old food was possibly the source of the allergen. Foods are then re-introduced slowly (and reactions monitored closely) to see if the offending ingredient can be pinpointed.

Which diet is right for your pet?

There are many options available for prescription limited ingredient diets, and the best option for a particular pet will be based specifically upon what ingredient(s) the pet is allergic to. It can be very difficult in some cases to determine which ingredient a pet may be reacting to. The top offending food items for dogs include beef, milk, lamb, wheat, corn, chicken egg, soy, and chicken. For cats, the list also includes tuna and salmon.

Several pet food manufacturers - such as Hill's, Royal Canin, and others - have developed clinical nutrition diets available through veterinarians and specially formulated to help dogs and cats with skin conditions and digestive discomfort due to food sensitivity. Your veterinarian can help determine what your pet may be allergic to and what diet would be the most appropriate for your pet.

What about store-bought "Limited Ingredient Formulas?"

Enthusiasm for limited ingredient diets has now found its way into commercial non-prescription diets. While these often contain more than a single source of protein and/or carbohydrate, and are not a replacement for a veterinarian-guided hypoallergenic food trial, they may be an interesting option for people simply wanting to try a diet with fewer ingredients.

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