How Important is Diet for Pets with Cancer?

Joanne Lynn Intile, DVM, MS, DACVIM
Published: January 16, 2014
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I’ve been asked to re-visit the idea of nutritional support for the veterinary oncology patient. I’ve previously discussed some of the basics of this topic in another article, Feeding Special Needs Pets: Cancer and a Healthy Diet for Pets.

Few things elicit as much controversy in the veterinary profession as the topic of nutrition. For owners of pets with cancer, nutrition tends to be the one variable an owner can control in an otherwise uncontrollable situation.

Owners cannot control their pets’ diagnosis. They cannot control when the cancer arose, or where it will decide to spread. They cannot control available treatment options or side effects. They cannot control prognosis. They can, however, control the food their pets ingest.

I’ve been charged with being “close-minded” with regard to the importance of diet for cancer patients, yet I argue that based on how I live my own life, I possess a greater than average recognition of how nutrition, fitness, and balance are all crucial to a healthy lifestyle. As a medical professional, I simply question how successful minor changes in only one of these parameters are going to be after the diagnosis of cancer is made.

Studies show a diagnosis of a life-threatening health issue is a strong motivator for a person to alter his or her own lifestyle habits. People “suddenly” become aware of how good nutrition, exercise, rest, and limiting stress can be on their overall wellness plan once diagnosed with disease. Ironically, many of those diseases are known to be associated with poor lifestyle choices (e.g., smoking and the risk for lung cancer, or obesity and the risk for diabetes).  Experience tells me that owners treat their pets in much the same way.

There is a lack of evidence-based information necessary to make substantial conclusions when it comes to diet and cancer in animals.  When this occurs, we veterinarians typically examine the standard of care in people and model our recommendations off of those parameters.

The American Cancer Society (ACS) guidelines acknowledge that “Many persons with advanced cancer may need to adapt food choices and eating patterns to meet nutritional needs and to manage symptoms and adverse effects such as pain, constipation, and loss of appetite.” Yet, a recent study investigating the quality of published reviews of nutrition and cancer in people found that 90 percent of the reviews published in 2008–2009 were “methodologically troublesome or frankly unsound.”

The most popular question I’m asked is in reference to feeding pets with cancer a low-carbohydrate, high-fat diet. The science behind this concept is illustrated by the “Warburg Effect,” which describes the observation that cancer cells preferentially obtain their energy from the metabolism of glucose to lactate, rather than utilize oxidative phosphorylation, the more typical energy-producing machine of healthy cells, that can be fueled by glucose, amino acids, fatty acids, or alcohol.

It’s unclear if what transpires in petri dishes applies to an intact living organism, but the “low-carb” diet is often erroneously touted as the “cure all” for pets with cancer. I agree the science makes sense, and formulating a diet comprised primarily of high quality protein, with limited carbohydrate sources, is sensible for any individual. The unanswered question is: “Will altering a pet's diet after being diagnosed with cancer ultimately alter the course of disease?”

I also find it difficult to embrace the notion that a “pan-cancer” low-carbohydrate diet would be balanced and appropriate for all pets with all stages of disease going through all different treatment protocols. The idea that there is no one specific “cancer” diet is well understood in human medicine, and it’s also well established that there is insufficient data available to address this concern more specifically. It’s very likely that the nutritional requirements would depend on an individual diagnosis of cancer.

Pets with lymphoma likely have different requirements compared to pets with amputations from bone tumors versus pets with cancer of their gastrointestinal tract. Pets undergoing certain chemotherapy drugs would likely have different needs than others undergoing radiation therapy or no therapy at all. Senior pets likely have different needs than younger ones. Perhaps even gender or breed would also influence overall nutritional requirements.

I also find it fascinating how owners are quick to ask me about dietary recommendations, but rarely, ask about how exercise could play a role in their pets’ health. In fact, I’m more frequently asked about placing restrictions on their pets’ activity because they now have cancer and may be “weak” or “immunosuppressed.” In my opinion, diet and exercise are inextricably linked and you cannot consider the wellbeing and health of a person or a pet without considering the two as one.

I recognize my opinion on this subject is likely not in sync with what the average pet owner is looking for when seeking advice on how to “holistically” treat cancer. However, as a practicing veterinarian, I must ensure my treatment choices are both medically sound and evidence-based to verify that I am truly making a difference in my patients’ outcome.   

The best advice I can provide is the “buyer must beware,” even when it comes to issues of veterinary oncology. You may be able to control what goes into your pet's mouth, but this should not come at a loss of control over your ability to recognize and accept fact over misrepresentation.

In the meantime, I promise to keep up with research, and anxiously await some solid information about nutrition and cancer in pets so I can be confident in my recommendations. I’m open to suggestions, and welcome your experience and knowledge in the comments, but I’m also going to need to critically review the data before I’ll be comfortable endorsing any particular diet plan or supplement.

If I can respect your viewpoint on things, hopefully you can respect mine.

Dr. Joanne Intile

Image: Kachalkina Veronika / Shutterstock