The Dog Aging Project is an expansive research initiative that is following tens of thousands of companion dogs for 10 or more years with the objective of identifying biological, environmental, and lifestyle factors that extend the healthy lives of dogs.
By the time we hit send on this email, there will be 75 published studies associated with The Dog Aging Project. And with their team of more than 75 researchers, numerous more publications are coming down the pipeline. This month, we are highlighting just one of those studies, published in the May/June issue of the Journal of Veterinary Internal Medicine, titled “Association between diet type and owner-reported health conditions in dogs in the Dog Aging Project.”
Katie Tolbert, DVM, PhD, DACVIM (SAIM, Nutrition), is an associate professor at the Gastrointestinal Laboratory at Texas A&M University and is a member of the Dog Aging Project (DAP) consortium. Her clinical interests and research program are focused on the treatment of acute and chronic gastrointestinal diseases in dogs and cats. Katie Kerr, PhD, professor of biostatistics at the University of Washington and member of the DAP consortium, served as the co-corresponding author for the paper.
Dr. Tolbert discusses some of the takeaways from this study, insights on how to interpret data from cross-sectional studies, and potential future directions on this topic.
Editor’s Note: This is an excerpt from Research Wrapped, a free monthly newsletter that collects the latest scientific research relevant to small animal veterinarians and pulls out practical takeaways. To be the first to receive this newsletter each month, subscribe here.
Using data from 27,487 dogs, the team analyzed the association between dogs fed a homemade cooked, commercial raw, homemade raw, or extruded diet and 13 owner-reported health condition categories. Was any one association particularly surprising or unexpected?
Dr. Tolbert: We were initially surprised to find that dogs fed home-cooked diets were more likely to have owner-reported gastrointestinal (GI) conditions. Upon further reflection, we hypothesized that this association likely reflects reverse causation—many dogs are switched to home-cooked diets as a therapeutic intervention for existing GI disease rather than the diet causing the condition. This highlights a key limitation of cross-sectional studies where data collected at a single time point can make it difficult to determine whether diet influences health outcomes or whether health problems drive diet choices.
As you just mentioned, this is a cross-sectional study; it is survey-based with an enormous amount of data (on a topic with very little published data). What is the most important takeaway that primary care veterinarians might use while communicating with clients who are electing to feed alternative diets?
Dr. Tolbert: The most important takeaway is that dietary recommendations should be individualized based on each pet’s specific health status, life stage, and the client’s circumstances and preferences. Rather than making blanket recommendations for or against alternative diets, veterinarians should engage in collaborative discussions with clients about potential benefits and risks for different feeding approaches. This study’s large dataset provides valuable insights into associations between diet types and health conditions, but these population-level findings don’t necessarily apply to every individual dog. The key is to help clients make informed decisions that consider their pet’s unique needs, their ability to safely prepare and balance homemade diets, and the need for ongoing monitoring for any health changes regardless of the diet chosen.
What do you think is the study’s biggest limitation?
Dr. Tolbert: The study’s biggest limitation is the potential for reverse causation—owners may have selected specific diets as therapeutic interventions for existing health conditions, meaning disease influenced diet choice rather than diet causing a health outcome. That is particularly relevant given that many alternative diets are commonly recommended or chosen as management strategies for various health issues. Because this is a cross-sectional study capturing data at a single time point, we cannot determine the temporal relationship between diet and health status, which prevents us from drawing causal conclusions. While our large dataset is valuable for generating hypotheses about diet-health associations, definitive conclusions about causation require controlled, longitudinal studies that can track changes over time. This limitation applies not only to our study but to all cross-sectional research in this area, regardless of where it’s published.
Editor’s Note: This is an excerpt from Research Wrapped, a free monthly newsletter that collects the latest scientific research relevant to small animal veterinarians and pulls out practical takeaways. To be the first to receive this newsletter each month, subscribe here.
Knowing what you know now, how would you develop and approach a subsequent study?
Dr. Tolbert: With 4 years of longitudinal data now available from DAP participants, we would design a prospective cohort study that tracks the same dogs over time to establish temporal relationships between diet and health outcomes. That approach would allow us to identify dogs that switch diets during the study period and monitor whether health conditions develop after diet changes, or conversely, whether dogs with new health diagnoses subsequently change their diets. We would also want to capture more detailed information about diet transitions, including the reasons for switches, duration of each diet type, and any veterinary involvement in dietary recommendations. Additionally, we’d aim to include more objective health measures alongside owner-reported conditions and potentially incorporate veterinary medical records to validate owner reports. This longitudinal design would help us move beyond associations to better understand causal relationships while also allowing us to examine dose-response relationships and identify particularly vulnerable or resilient subpopulations of dogs.
The Study
Association between diet type and owner-reported health conditions in dogs in the Dog Aging Project.
Ortiz AV, Luo I, O’Brien J, et al. J Vet Intern Med. doi:10.1111/jvim.70060