Review: Changes in diet and supplement use in dogs with cancer

The Journal of Veterinary Internal Medicine recently published a small companion animal caregiver survey study from the University of California, Davis Veterinary Medical Teaching Hospital (UCD) about potential dietary changes they sought after their companion dog’s cancer diagnosis. We relay our thoughts below.

First, we agree with the authors regarding their stated limitations of the study. They only captured 120 completed surveys out of 438 distributions, but included an additional eight for analysis that completed the section regarding diets. (The last two sections pertained to supplements and treats.) This survey lacks geographical, cultural and demographic differences because UCD only garnered answers from its clientele. Also, as the cost of treating companion pet cancer care is very expensive, many companion pet parents seeking oncological care for pets typically have higher incomes.

The Beginning

When we began reading, we noted that the authors adopted the conservative approach against low carbohydrate diets or home-prepared meals for dogs suffering with cancer. Their rationale was lack of studies and being potentially nutritionally incomplete, respectively.

Then, the paper digressed, which prompted us to look more closely at the numbers.


Directly quoting from their text, “There has been considerable attention to the association between dilated cardiomyopathy (DCM) in dogs and the use of grain-free diets, and both veterinarians and pet owners might have increased awareness of this issue. Regardless, given that more than 1 in 5 dogs in the present study were fed a grain-free diet before a cancer diagnosis, this data highlights the need for clinicians to discuss the risk of diet-associated DCM with all dog owners.”

To be clear here, DCM is not cancer. It is a type of heart disease. Specifically, it is the loss of muscle function or strength involving the heart’s left ventricle.

We have written extensively about the DCM debate. For practically every study stating that grain-free diets cause DCM, another study pokes holes in or disproves the first study. The opposing studies are often more thoroughly devised, which reflects the complexity of canine nutrition. Even the Food and Drug Administration (FDA) wants “meaningful research.”

Dietary Changes

Once we read the statement, which could alarm the audience, “more than 1 in 5 dogs in the present study were fed a grain-free diet before a cancer diagnosis…” We delved into the numbers.

Let’s flip the statement: more than 1 in 5 dogs. The “more than” is actually 22% in this study. So, that means that more than 3 in 4 dogs (78%) were fed a grain-inclusive diet prior to cancer diagnosis and visit to UCD.

Prior to diagnosis (n=128):

  • 7% (n = 93) of dogs were fed commercial diets exclusively (unknown: kibble, raw, dehydrated, fresh direct, canned);
  • 1% (n = 4) of dogs were fed home-prepared diets exclusively; and,
  • 2% (n = 31) were fed a combination of commercial and home-prepared diets.

After diagnosis:

  • 4% (n = 76) of dogs were fed commercial diets exclusively;
  • 0% (n = 9) of dogs were fed home-prepared diets exclusively;
  • 6% (n = 43) were fed a combination of commercial and home-prepared diets;
  • Significant increase in proportion of dogs fed at least some home-prepared foods as part of their diet after the cancer diagnosis (27.3%-40.6%, P = .03);
  • No significant difference in the proportion of dogs fed any portion of their intake from a commercial diet after the cancer diagnosis (96.9% vs 93.0%, P = .25); and,
  • Many dogs fed commercial diets both before and after diagnosis changed commercial formulas; out of 49 respondents that provided this information for both timepoints, 23 switched diets (47%).

Indeed, they included a table specifically for “special diets”.

Special diets prior to cancer diagnosis:

  • 22% of dogs were fed a grain-free diet;
  • 7% of dogs ate a raw food diet;
  • 16% of dogs ate a diet for a medical condition (for what condition?);
  • 5% of dogs ate organic diets;
  • 2% of dogs were fed vegan diets; and,
  • 1% of dogs were fed vegetarian diets.

The study authors became focused on the grain-free and home-prepared diet issues, such that their comments appeared skewed.

For example:

  • “Kibble” is mentioned in the text only once;
  • “Raw” is mentioned four times;
  • “Grain-free” is mentioned eight times;
  • “Grain-based” or “grain-inclusive” is never mentioned; and,
  • “Home-prepared” is mentioned 31 times.

Disclaimer and Conclusion

Can types of diets and certain foods contribute to the onset of cancer? Yes. Does that subject need to be explored? Yes; the data the study authors provided documents the need for more research studies.

A significant limitation of this study is that it only reflects canine patients seen at UCD with cancer. In that context, what is the percentage of dogs fed kibble diagnosed with cancer compared to the entire population of dogs fed kibble?

Furthermore, the authors could have compared those percentages to the other foods. For instance, is the percentage of dogs fed kibble and diagnosed with cancer greater, the same or less than the dogs fed raw and diagnosed with cancer?

Yet, according to their data, 72.7% of dogs with cancer and clients of UCD – the majority – were fed commercial diets prior to cancer diagnosis. 78% were fed grain-inclusive diets prior to diagnosis.

Final Note

Dogs with certain types of cancers should not be fed a raw diet, but rather a home-prepared, canned, freeze dried, or dehydrated diet. Please speak with your veterinarian when switching companion pet foods.


Kramer, Matthew L et al. “Changes in diet and supplement use in dogs with cancer.” Journal of Veterinary Internal Medicine, 10.1111/jvim.16825. 9 Aug. 2023, doi:10.1111/jvim.16825,

Fougere, Barbara. “Raw Food, Wholefood and Commercial Diets – Where’s the evidence?” American Holistic Veterinary Medical Association Journal, vol. 36, summer 2014, pp. 8–14.

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