In early 2018, researchers at Cornell University's College of Veterinary Medicine (CVM) began an ongoing study to evaluate the effectiveness of dietary changes in treating persistent gastrointestinal (GI) problems (aka chronic enteropathy) in dogs.
Most dogs with these types of chronic GI issues have a condition called lymphocytic plasmacytic enteritis, a form of inflammatory bowel disease (IBD). According to lead study investigator Kenneth Simpson, professor in the CVM's Department of Clinical Sciences, up to 80% of dogs with this disease respond well to changes to their diet.1
Unfortunately, most dogs with IBD "undergo a whole slew of best-guess treatments as owners and veterinarians try to give them relief," says Simpson. It has been my experience that too often, these best guesses involve multiple rounds of unnecessary antibiotics and/or corticosteroids, because veterinarians aren't trained to look first at what their GI patients are being fed. These drugs are often not only unhelpful, but they exacerbate the underlying disease.
Veterinarians who include dietary changes in their treatment plans typically recommend ultra-processed diets that are presumably easier to digest or that contain a different type of meat than the dog has been eating. Increasingly, they're also prescribing ultra-processed diets containing hydrolyzed proteins that have been chemically "smashed" into smaller pieces to avoid stimulating the immune system. According to Simpson:
"… no one really knows why or how these diets work or why the original diet caused clinical signs. We don't know the optimal way to manage those dogs."
In my opinion, switching from one ultra-processed food to another provides only a temporary respite from GI issues, and in most cases, those issues will resurface eventually. More about this shortly.
Dogs in the Study Are Fed One of Three Processed Diets
Dogs participating in the study are recruited from the CVM animal hospital as well as referring veterinarians. They're separated into three groups, two of which receive hydrolyzed protein diets, with the remaining control group eating a "high-quality maintenance mixed-protein diet."
All three diets contain the same balance of carbohydrates, protein and fat, and are supplied to the dogs' owners at no cost by Farmina, an Italian pet food company that is also sponsoring the study.
A separate fourth group of dogs with a disease known as protein-losing enteropathy are also part of the study. These dogs are much sicker overall and present a significant treatment challenge because many of them refuse to eat the prescribed diets. For the study, this group receives either of the two hydrolyzed diets, and the primary goal is to increase their interest in eating and help them gain weight.
Dogs who fail to respond after two weeks can be moved to another group receiving a different diet. Once a dog is responding well to a given diet, he or she stays on it for at least three months, ideally six or more to see if any changes are maintained.
Researchers: Study Results to Date Have Been Positive
According to the researchers, the results of the study so far are encouraging and even "dramatic" for many of the dogs. One example is a Briard rescue named Buddy, who was always full of energy until he suddenly began having serious digestive and elimination issues. His owner had been searching for answers for two years by the time Buddy joined the protein-losing enteropathy study group at Cornell.
Today, at 13 and despite his low protein levels, the dog is much improved. According to his owner, Buddy has nearly consistently solid stools, rarely has gas, has regained 25 pounds, and seems much more comfortable and less restless.
Gabby, a long-haired miniature Dachshund, suffered from colitis for most of her seven years. Her owner described her as "sick, limp, and listless," and was frustrated by "trying and failing with numerous prescription diets and medication."
Since beginning the study, Gabby has suffered only a couple of bouts of bloody vomit or stool — previously an almost daily occurrence — and she has more energy. "Feeding is much easier since I don't have to hide antibiotic powder in her food anymore," says her owner.
Hydrolyzed Protein versus Intact Protein Diets
Simpson and his colleagues are happy with their preliminary study results but are also somewhat surprised, apparently in part because they expected the dogs on the hydrolyzed diets to do much better than the dogs in the control group, who are fed regular maintenance diets.
"Conventional wisdom would suggest that the hydrolyzed diets would do better and dogs on the intact mixed-protein maintenance diets would fail to respond," he explains. "Yet, at three months, almost all dogs, independent of group, have had positive responses, which means the placebo group is performing equally well."
My guess is that almost any change in the dogs' diets would bring about a temporary improvement in their conditions as a result of the removal or replacement of a certain percentage of potentially problematic ingredients.
It should also be noted that according to Farmina's website, the company uses only natural preservatives and no genetically modified organisms (GMOs) in pet food formulas.2 It's very likely some of the study dogs were reacting specifically to synthetic preservatives and/or genetically modified ingredients in their pre-study diets. Simpson hypothesizes that:
"… while we are still in the dark about what's driving adverse reactions to food in dogs, the positive responses to a high-quality, intact mixed-protein-source diet suggest they are not a simple allergic response to intact protein. Perhaps non-protein ingredients or additives may be causing adverse reactions."
I agree with Simpson's supposition that today's epidemic of GI issues in dogs (and cats) isn't as simple as an allergic response to intact proteins; however, I do think factory-farmed meats present a problem for many pets.
And I definitely feel that all the "non-protein ingredients" and other additives found in ultra-processed diets are a foundational problem, along with the changes that occur to ingredients subjected to high heat processing, including the formation of Maillard Reaction Products (MRPs), including advanced glycation end products (AGEs) that create gut inflammation in animals.3
What I Believe Causes Food Sensitivities in Dogs
Before I discuss food sensitivities/allergies, it's important to be aware that for dogs with IBD, leaky gut (dysbiosis), or some other significant GI disorder, until the underlying disease is identified and healed, it's unlikely that treating food sensitivities alone by rotating diets will be successful.
Leaky gut has a myriad of causes in pets, with the most recently discovered culprit being toxic household dust. If you're still using Teflon pans, home scenting products (plug-ins and room sprays) and regular (non-organic) cleaning products, now is the time to set greener New Year's resolutions. The chemically laden dust in your home and the dust mites it attracts may be contributing to gut inflammation in your pet.4
As the tight junctions of the intestines break down, the first response is for the body to release fluid into the intestines in an attempt to flush the irritants out. Diarrhea is the result: nature's attempt to rid the body of harmful substances. One round of the most common treatment for diarrhea, the antibiotic Flagyl (metronidazole), and research demonstrates dysbiosis (microbiome imbalance) is the outcome for most pets.5
Add in monthly oral administration of flea and tick pesticides that negatively affect the microbiome and the repeated prescribing of more antibiotics without appropriate diagnostics, and it's easy to see why many pets in modernized countries end up with recurrent gut issues and "chronic enteropathies."
Chronic GI inflammation sets the stage for systemic food intolerances and potential food allergies, because the gut leaks contaminants and partially digested food particles into your pet's body, triggering a cascade of problems.
If the gut allows enough foreign particles into the body, your animal's immune system may perceive that something in her diet is attacking her body. To deal with the "threat," the immune system launches a counterattack just as it would against a real danger, for example, an infectious agent.
Certain substances in the diet are more likely to trigger the immune system than others, and unfortunately, the nutrient your carnivorous pet needs most — protein — is very often the culprit. Many integrative veterinarians have discovered protein reactions are much less severe or disappear with the protein is "clean" (not factory farmed) and unprocessed (raw).
Although no research has been published on why carnivores develop sensitivities to protein, we suspect foreign contaminants and food processing byproducts may be the reason. Growth hormones, antibiotics, chemical residues and MRPs may actually be the triggers, and not protein itself.
If we had multiple generations of pets raised exclusively on organic, clean, fresh, species-specific diets, we could conduct studies to determine if they also develop sensitivities to meat proteins. If this population of animals did not develop intolerances to the proteins in their diet, our suspicions about foreign contaminants and heat processing byproducts would be confirmed.
However, since 99.9% of pet foods are made with conventionally raised, factory-farmed meats (and only the leftover, rendered pieces and parts that fail to become human food), blended with glyphosate-contaminated fillers known to disrupt the microbiome,6 sensitivities will continue to be a problem for almost all susceptible pets.
And to compound the problem, often it isn't until the GI tract has been significantly compromised by the inflammation caused by a food intolerance that a dog begins to show symptoms of digestive disturbance.
Pets fed the same food day in and day out for a period of months or years can develop a sensitivity to not only the protein source, but also grains and vegetables.
If the food is made from inexpensive feed-grade raw materials (which describes the vast majority of pet food) and is highly processed (the vast majority of kibble has been cooked 4 times before reaching the bag), chances are the meat contains high levels of advanced glycation end products (AGEs), which in addition to antibiotics and hormones can prompt the immune system to overreact and cause massive systemic inflammation.
These dogs also often grow sensitive to other reactive ingredients in the food, typically inflammation-creating grains and other refined carbohydrates. Many grains have been genetically modified and sprayed with glyphosates, which can compromise the gut barrier and contribute to dysbiosis.
Certain breeds of dogs are more sensitive to the damaging effects of grains on the gut,7 but because pets don't need any starch to begin with, most do best with a grain free, low carb/starch diet to address and prevent gut problems.
My Approach with Dogs with Suspected Food Intolerances
The first thing I recommend for animals over the age of 12 months who I suspect are dealing with a food sensitivity is a NutriScan saliva test. If the first thing your own veterinarian recommends is antibiotics and/or a highly processed prescription diet, I suggest you order a NutriScan test instead. I also suggest finding an integrative veterinarian who will work with you to identify the root cause of your pet's condition and develop a customized healing protocol.
The NutriScan panel tests for 24 purified food extracts that recognize 56 food ingredients, and the results can often identify the specific ingredient(s) in your pet's food that are causing a problem, which makes it much easier to customize a diet to resolve the issue.
When an animal is having a reaction to something in her diet, her body needs a break from that food. After determining your dog's food sensitivities with a NutriScan test, my recommendation is to introduce a novel diet to promote healing. This means transitioning her to a different food she isn't sensitive to containing ingredients her body isn't familiar with.
Unfortunately, many dog foods claiming to contain "novel proteins," don't. In addition, pet food mislabeling is a widespread problem, so if you're planning to go with a commercially available processed novel diet, be aware it will undoubtedly contain ingredients you're trying to avoid.
The safest approach, at least for the first few months, is home-cooked meals that allow you to control virtually everything that goes into your dog's mouth. Second best is a human grade commercially available fresh food containing an uncommon protein, produced by a company you trust.
It's very important that all suspect foods be avoided for at least several months. Oftentimes animals experience a reaction to both the primary protein and carbohydrate sources in their diet. In addition to avoiding all potentially problematic foods, it's important to reduce or eliminate any "filler ingredients" (as well as synthetic nutrients) that can play a role in food sensitivities and inflammatory conditions.
I also believe pets with food intolerances do best on a very low-starch diet. Starches (aka soluble carbohydrates) are pro-inflammatory to the body and can exacerbate GI inflammation. Microbiome expert Dr. Holly Gantz has also seen beneficial changes in pets' microbiomes when excessive carbs are reduced.
Until new labeling standards are fully in effect, pet food manufacturers aren't required to list carbohydrate content on their labels, so you have to calculate it yourself. It's worth taking the time to do this before choosing a novel diet (less than 20% carb content is the goal).
Returning Dogs to a Regular Diet
A dog with food sensitivities should remain on a novel diet for a minimum of 2 months and preferably 3, to allow the body time to clear out the allergenic substances and begin the detoxification process.
During this 3-month period I also typically address dysbiosis with the appropriate probiotics, microbiome restorative therapy and nutraceuticals. If your pet has had multiple rounds of antibiotics, assessing the microbiome and beginning microbiome restorative therapy can be life-changing. This is where partnering with a functional medicine veterinarian that has experience in healing dysbiosis is important.
Because each case of food intolerance is unique, again, I recommend a custom formulated protocol created by a professional that understands your pet's unique set of circumstances. Once a patient has completed 2 to 3 months on a novel diet, other foods can be slowly reintroduced one at a time while the dog's response is closely monitored.
Some pets show dramatic improvement on the new diet, and in those cases, I often don't rush the reintroduction of food that could be problematic.
When the animal is stable and doing well, I encourage pet parents to find at least 1 and preferably 2 other protein sources their pet tolerates well so that every 3 to 6 months, they can rotate proteins and hopefully avoid further intolerances.
In addition, I believe the "cleaner" the proteins, the less chance your pet will become sensitive to them over time. Clean animal proteins are non-toxic, no chemical residues to contend with. For example, food animals raised on a natural diet (grass-fed, not factory farmed), as well as hormone-free animals, are better food sources for sensitive pets.