What the study looked at
Researchers analyzed data from 27,478 dogs enrolled in the Dog Aging Project, a large long-term study of canine health. They compared dogs eating different types of diets - standard dry kibble (extruded), homemade cooked food, commercial raw food, and homemade raw food - to see if there were any differences in owner-reported health conditions. The goal was to identify potential associations between diet type and disease.
Key findings from the study
The study found that dogs fed a homemade cooked diet were more likely to have several types of health problems compared to dogs eating kibble. Specifically, they had higher rates of:
- Gastrointestinal disease (such as chronic diarrhea, vomiting, or inflammatory bowel disease)
- Renal and urinary disease (kidney problems, urinary tract infections)
- Hepatic and pancreatic disease (liver issues, pancreatitis)
In addition, dogs eating a commercial raw diet were more likely to have respiratory disease. No significant associations were found for homemade raw diets, though the number of dogs on that diet was smaller.
Important: correlation is not causation
This is a cross-sectional study, which means it looks at a snapshot in time. It can show that two things are linked (correlation), but it cannot prove that one causes the other. So we cannot say that homemade cooked diets cause these health problems. There are other possible explanations.
The problem of reverse causation
One major possibility is reverse causation. This means that owners may switch their dog to a homemade diet because the dog already has a health issue. For example, a dog with chronic digestive problems might be put on a home-cooked diet in hopes of improving symptoms. In that case, the diet didn't cause the disease - the disease prompted the diet change. The study's authors specifically note this as a limitation.
What this means for dog owners
If you feed your dog a homemade cooked diet, don't panic. This study does not prove that homemade food is harmful. However, it does highlight that homemade diets can be tricky to get right. It's easy to create nutritional imbalances if the diet isn't carefully formulated. A poorly balanced homemade diet could contribute to health issues over time. On the flip side, a well-formulated homemade diet, especially one designed with a veterinary nutritionist, can be perfectly healthy.
Practical takeaways for dog owners
- If your dog is healthy on a homemade diet, there's no need to switch. But do make sure the recipe is balanced. Consider consulting a board-certified veterinary nutritionist.
- If your dog has health issues and you're considering a homemade diet, talk to your vet first. The diet might help, but it needs to be tailored to your dog's specific condition.
- For all dogs, regular vet check-ups are essential. Bloodwork and urine tests can catch early signs of kidney, liver, or other problems.
- Be cautious with raw diets. The study found a link between commercial raw food and respiratory disease, possibly due to bacterial contamination. Raw diets also carry risks for both dogs and humans from pathogens like Salmonella.
What this study doesn't tell us
This study only looked at associations, not cause and effect. It didn't measure the nutritional content of the diets or how long dogs had been on them. Future research should follow dogs over time to see if diet changes precede or follow disease. The Dog Aging Project is ongoing, so we may get more answers in the future.
Bottom line
This large study adds to our understanding of how diet may relate to dog health, but it's just one piece of the puzzle. The best diet for your dog depends on many factors, including age, breed, health status, and lifestyle. Work with your veterinarian to make informed choices. And remember: correlation is not causation.
Sources
- Varela Ortiz A et al. (2025). Association between diet type and owner-reported health conditions in dogs in the Dog Aging Project. Journal of Veterinary Internal Medicine. Read the full study