Hydrolyzed Soy in Dog Food

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I was recently updating some pet food recipe information in our pet food database and happened to be updating a handful of prescription recipes when I noticed the ‘allergen free’ and ‘hypo allergenic’ (and similar) foods. Most of these types of foods use hydrolyzed proteins as a key ingredient that is the cornerstone of the hypo allergenic recipe. Although I generally understand the theory behind using a hydrolyzed protein to combat allergies, I am perplexed by the types of proteins that are typically hydrolyzed, specifically, soy.
Hydrolyzed Soy

What is Hydrolyzed Protein?

Hydrolyzed protein is protein that has been hydrolyzed or broken down into its component amino acids. As the name implies, the process of hydrolysis will include adding water to separate the amino acids.


The theory behind using hydrolyzed proteins in pet food is based on the idea that when the protein is broken down into such small components, it will no longer be recognized by the immune system as an allergen.   Hence, if a dog is allergic to chicken, the dog’s body might not react to hydrolyzed chicken since the dog’s body won’t recognize it as the offending allergen, Thus, (again in theory), a pet could be fed the same protein that they are allergic to without any of the allergic reactions.


I am personally not a fan of this approach to treating food allergies. If a dog has a known food allergy, wouldn’t it make more sense to identify those allergies and then feed them healthy foods that contain alternative protein and carbohydrate sources? There are plenty of pet food choices out there that contain alternative proteins like rabbit, pork, and salmon.


And why would a dog parent want to switch their dog to a food with hydrolyzed soy? Soy is not an appropriate ingredient for dogs to begin with and unless the dog had a known allergic reaction to soy, why bother hydrolyzing it? Heck, if a dog is allergic to soy, stop feeding them soy! (I would suggest every dog parent should avoid soy).


Dr. Katy Nelson, DVM and host of The Pet Show with Dr. Katy Nelson, is not a big fan of using the available prescription diets to treat food allergies. “In my many years of veterinary practice, I have never prescribed a prescription food containing hydrolyzed proteins. Instead, I recommend that the pet parent choose a food with a novel protein and high quality ingredients. In the past, I have even recommended Kangaroo based foods, which certainly qualify as novel.”, said Nelson. “In my experience, dogs do not do well on hydrolyzed diets. I notice that they don’t look good, there coats look terrible, and they are very susceptible to diarrhea and other gastrointestinal issues when fed this kind of food.”


According to Dr. Nelson, if a hydrolyzed protein diet is chosen, there is no sound rationale for using soy as the hydrolyzed protein, since soy is not an ingredient that she would recommend to her patients any way.


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  1. I think the theory behind hydrolyzed protein makes perfect sense. First question would be how well is the protein broken down. Is it really individual amino acids or protein chinks (peptides)? And if protein chunks, wouldn’t they still bee allergenic?

    Other than that it’s an awesome theory. Up here we have a digestive enzymes product that claims to do the same thing (though within the digestive system rather than before the food hits the mouth). The theory behind it is the same.

    It’s a perfectly good theory.

    I agree that soy wouldn’t be my choice of protein hydrolyzed or not.
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  2. Didn’t know they hydrolyzed soy either. hmmmm
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  3. Ick, soy, in whatever shape or form, should definitely not be fed. I know a few dogs who are fed a prescription diet and their coats DO look incredibly dull. I would never feed my dogs that kind of crap.
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  4. This is interesting. I still haven’t figured out whether Haley’s allergies are environmental or food-based (or both), but anything we can do to help decrease symptoms helps and I definitely don’t want to feed her any type of food that’s unhealthy but claims to be better for allergies.
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