The trials of therapeutic diets

Tackling the complicated issue of dermatologic disease through food

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Client misconceptions and behaviors can be the biggest barrier to successful outcomes when prescribing therapeutic diets for dermatologic disease.

“Pet owners are more likely to think that their pet has a food allergy than environmental allergies,” said Cailin R. Heinze, VMD, DACVN, assistant professor of nutrition at Tufts University’s Cummings School of Veterinary Medicine in North Grafton, Mass. “I think the marketing of pet food, like marketing grain-free diets for pets with allergies, and marketing all these exotic proteins and limited-ingredient diets make pet owners think that food allergies are much more common than they actually are. Probably 90 percent of the allergic disease we see in dogs is not related to food—maybe even a higher percentage.”

“Some of the common diet misconceptions that I hear from clients are a) raw food is healthier, b) grain-free is better, and c) higher protein foods are ‘hot’ leading to ‘hot spots,’” said Jon D. Plant, DVM, DACVD, owner of SkinVet Clinic in Lake Oswego, Ore.

Another obstacle is clients who expose their itchy pets to many different ingredients by frequently switching between different over-the-counter diets in an effort to identify an agreeable diet on their own. This makes it extremely difficult to take a detailed diet history and identify a novel diet for food elimination trials.

“Many owners take it into their own hands to diagnose their pet with food allergic disease and they’re doing it incorrectly,” said Martha G. Cline, DVM, DACVN, president of the American Academy of Veterinary Nutrition.

Some pet owners regularly rotate their pet’s diet, even if the pet is not showing signs of an adverse food reaction. This is either in a misguided effort to “fend off” the development of food allergies down the road or simply to provide more variety in their pet’s diet because they themselves wouldn’t want to eat the same thing every day. This it difficult to identify novel protein and carbohydrate sources for an elimination trial if the pet skin disease.

“We have no data that says that if you change protein every so many days you’re going to prevent a food allergy,” said Dr. Heinze said. “My advice to puppy owners is to not feed anything exotic, to avoid diets that have four and five different protein sources in them, and to try and feed simpler diets.”

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“Maybe they rotate between a chicken diet and a beef diet, but there’s absolutely no reason to feed duck or alligator or wild boar to a normal, healthy puppy,” Heinze said. “The whole concept of a pet food is that they’re designed to meet the nutritional needs. Baby formulas are probably the closest comparison—they’re designed to meet all of the nutrient needs for that life stage.”

Clients might balk at the expense of a hydrolyzed therapeutic diet, but in many cases that is the best option if the patient has been exposed to many different diet ingredients or if the client can’t remember exactly what their pet has and has not been exposed to.

“I recommend a novel-protein diet when a client has a detailed diet history for the pet and we can feel confident that we are switching to a unique protein source,” Dr. Plant said. “When that is not the case, then I recommend hydrolyzed protein diets. For clients with the time and commitment necessary, a home-prepared novel protein diet can be an excellent choice.”

Home-prepared diets are not without their challenges.

“Often, the whole proteins that we have as options are exotic meats,” Heinze said. “I have a client who’s spending $15 per pound on bison and the dog is eating half a pound a day. That can get really expensive really fast.”

For some patients, a home-prepared novel ingredient diet is the only option, but it’s important to get the client completely on board.

“Some animals won’t eat a therapeutic diet get stuck doing a home-cooked diet,” said Dr. Cline. “It can be really tedious for pet owners to make their own food, especially when you’re dealing with a large-breed dog. Owners be aware of the amount of work that it may entail. It should be under the guidance of a veterinary nutritionist, and if they’re going to be on a home-prepared diet long term it needs to be complete and balanced.”

Ingredient contamination and serum testing

“A number of studies1 have been published in the past few years that report finding undisclosed protein sources in OTC limited ingredient and veterinary hydrolyzed foods,” Plant said.

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One study found DNA from one or more animal species other than those declared on the label in nine out of 10 OTC diets analyzed.2 Another study found soy antigens in three of four OTC diets claiming to be soy free and even veterinary therapeutic diets labeled soy free contained varying levels of soy antigen.3

Recent research investigating the accuracy of in vivo or in vitro tests for adverse food reactions has indicated that these tests showed low repeatability and, in dogs, a highly variable accuracy.4

“We did a study that showed lots of healthy dogs with no clinical signs of allergies were positive on these tests,” Heinze said. “I still see a ton of my clients come in with printouts of these allergy tests. Some of them are owner driven and the owners insist, but I think vets still recommend some of these tests because they hope that there are maybe some benefits to them.”

Ensuring client compliance

One of the biggest challenges of diet trials is owner compliance with the strict rules.

“We can recommend all we want, but owners are not going to be compliant,” Cline said. “I have a handout that I give to clients. I go over everything in the handout with them, but then I give them the printout and tell them to please read it when they get home in order to remind themselves.”

Heinze also uses handouts to help reinforce the diet elimination trial rules that lists dos and don’ts a might not think about.

“Giving them something so they have a reference for when they get home and they’re trying to explain it to their other family members can be helpful,” she said. “Make sure that they’re on board for doing it because doing a food trial and not doing it right …  you’re spending a lot of money potentially for a hydrolyzed diet, and then you’re ruining it. I can’t tell you how many pet owners that I end up seeing that are feeding a hydrolyzed diet and then adding chicken breast to it, which entirely defeats the purpose.”

These days, veterinarians are finding it more and more difficult to identify novel protein ingredients for elimination trials.

“Many of the novel protein diets that we are used to using are no longer novel because these protein sources are pretty ubiquitous in the over-the-counter market,” said Martha G. Cline, DVM, DACVN, who practices at the Red Bank Veterinary Hospital Healthcare Network, which has multiple locations in New Jersey, and is president of the American Academy of Veterinary Nutrition.

With lamb, bison, wild boar, and even kangaroo no longer rare in the pet food marketplace, veterinary therapeutic diet manufacturers are turning to more exotic protein sources like alligator. Alice Jeromin, RPH, DVM, DACVD, practice owner at Veterinary Allergy & Dermatology Inc., in Richfield, Ohio, presented on the topic at VMX 2018 in Orlando.

“Why consider alligator in a diet to rule out food allergy?” she asked. “Because we have run out of novel proteins for testing. Novel proteins are now hard to come by with the advent of over-the-counter limited-ingredient foods, [but] these diets are not suitable for use in testing for food allergies in pets as studies show they may contain additional ingredients not listed on the label.”

When using exotic proteins, Cailin R. Heinze, VMD, DACVN, prefers utilizing commercial veterinary therapeutic diets rather than home-prepared when possible.

“It’s hard to get nutritional information on bison or kangaroo or alligator or ostrich,” said Dr. Heinze, who is assistant professor of nutrition at Tufts University’s Cummings School of Veterinary Medicine in North Grafton, Mass. “If I don’t have a full nutrient panel, then I have to guess whether this diet is meeting the pet’s needs or not, or we have to spend a couple thousand dollars to analyze the diet. It’s also hard to get quality kangaroo in this country, and there’s been some questions recently about the nutritional value of kangaroo, so it gets very complicated.”

Alligator hasn’t hit the OTC marketplace yet, so veterinarians have a new novel source—for now.

“It may be coming eventually, and so I think that for some practitioners, including myself, find ourselves needing to use hydrolyzed protein diets,” Dr. Cline said.


1 bmcvetres.biomedcentral.com/articles/10.1186/s12917-018-1346-y

2 onlinelibrary.wiley.com/doi/10.1111/vde.12431/full

3 ncbi.nlm.nih.gov/pubmed/25251429

4 bmcvetres.biomedcentral.com/articles/10.1186/s12917-017-1142-0


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