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Nutritional Support of Dogs and Cats with Cancer

Patients with cancer of any type can be faced with several challenges, including side effects related to the presence of a cancerous mass, side effects of surgery (and possible complications of surgery, including wound infections, etc.) and side effects of other treatments, including chemotherapy and radiation therapy. All of these challenges can result in dietary intake that is lower than normal for the patient, and can cause weight loss, poor wound healing, and loss of appetite.

The internet contains a lot of advice on dietary recommendations for both humans and pets with cancer. Despite the certainty with which many dietary recommendations in cancer are made, our actual knowledge of the ideal diet – special nutrients and supplements included – is very small, with very little scientific evidence supporting many current popular recommendations.

What follows is a short list of recommendations proven to be of benefit for the cancer patient.

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  1. Ensure the patient receives its daily caloric requirements

This sounds simple – in that we should feed enough food to maintain the patient’s body weight, but there are some caveats:

  • For underweight patients: Patients in poor body condition should be fed sufficient calories to gain weight to an “ideal” body condition score (a score of 4.5/9 is considered ideal)
  • For overweight patients: Patients who are overweight should ideally lose weight until they reach an “ideal” body condition score (a score of 4.5/9 is ideal)
  • Weight gain above an ideal body condition score, in rodents and people, is associated with worsened outcome in cancer and can exacerbate co-morbidities, such as arthritis and heart disease.
  1. Feed a balanced and complete diet

Whilst many websites and books suggest or promote “cancer diets,” there is no evidence that any one diet is superior to another in managing patients with cancer, as long as the diet is complete and balanced and meets the nutritional requirements of the patient. Pets with cancer can be fed commercial diets, home-cooked diets (see below) or a combination.

  1. Home-cooked diets: If home-cooked diets are fed, they should be balanced and complete. The website BalanceIT ( contains a home-made pet food balancer, which enables users to create home-made diets that are nutritionally complete and balanced. Note that failure to ensure a home-made diet is balanced and complete, can result in nutrient excesses or deficiencies that may worsen the pet’s prognosis, either through cancer-related, or nutrient-related effects.
  2. Raw-food diets: Some sources recommend raw food diets for pets with cancer. It is very important to avoid feeding raw food diets or treats to pets with cancer, for a number of reasons:
  • Raw meat, eggs, and unpasteurised milk carry a high risk of bacterial contamination with Salmonella, Listeria, E. coli, Campylobacter, and many other potentially dangerous bacteria.
  • Freezing, or freeze-drying raw foods do not make raw foods safe, as many bacteria, and their toxins, survive the freezing process.
  • Patients with cancer are frequently immune-compromised. Pets undergoing surgery, chemotherapy and radiation therapy often have increased stress of their immune system, making them more likely to contract infection than healthy pets. Chemotherapy, in particular, often actively suppresses the immune system, making infection with bacteria extremely likely.
  1. What About Low-Carbohydrate Diets?

Low-carbohydrate diets have been recommended because in theory, depriving cancer cells of carbohydrates will deprive them of their main source of “energy”. While this has been proven in laboratory studies on cancer cells, there is currently no evidence that low-carbohydrate diets improve survival or cancer remission in clinical studies in dogs and cats.

Similarly, there is also no proof to support the notion that grains are worse for cancer than other sources of carbohydrates.

  1. What About Dietary Supplements?

Most dietary supplements have not been proven effective in the management of cancer in dogs and cats. Furthermore, dietary supplements vary widely in their concentration, bioavailability, and additives – making selection of dietary supplements fraught with inaccuracy.

Omega-3 fatty acids from fish oil (DHA and EPA) may be helpful for animals with cancer, although there are only a few peer-reviewed studies on benefits in dogs or cats at present. While some high quality commercial pet foods may contain enough omega-3 fatty acids from fish oil that giving additional supplements may not be necessary, other foods may not. If adding fish oil to a diet with lower omega-3 concentrations, be sure to use a supplement that has been independently tested for quality control. Additionally, be mindful of the fact that omega-3 fatty acids from plant-based sources do not have the same effect as fish oil omega-3 fatty acids. Also, remember that fatty acids contain calories (as many as 10 calories per gram) – meaning the diet you supplement may require feeding in smaller amounts to avoid unwanted weight gain.

Antioxidant supplementation in food fed to cancer patients is controversial, as they may reduce the efficacy of treatments like radiation therapy and chemotherapy on cancer cells. It appears, however, that supplementing antioxidants from food such as fruits and vegetables may be reasonably safe, but be sure to avoid foods that are toxic to dogs and cats, such as grapes, raisins, onions, garlic, chives, and macadamia nuts, etc.

What Does All This Mean?

The diagnosis of cancer in a dog or cat does not necessitate a change in diet. As long as caloric requirements are met, the patient is fed a complete and balanced diet and the patient has ideal body condition, other changes are not required.

It is important to avoid feeding raw foods – as many cancer patients are immune-compromised, and may develop severe illness with these foods.

If home-cooked diets are preferred by the client, it is essential these diets be assessed by a board-certified veterinary nutritionist, or by web-based calculators, to avoid unwanted deficiencies or excesses in the diet.

A list of helpful websites regarding nutritional supplements is included below:

  1. Consumerlab: Site (with a small subscription fee for use) that independently evaluates dietary supplements (primarily for human supplements but some pet supplements are included) com.
  2. Food and Drug Administration (FDA): Regulatory and safety issues of dietary supplements, adverse event reporting
  3. Mayo Clinic drugs and supplements information: Fact sheets on human supplements and herbs
  4. National Institutes of Health (NIH) Office of Dietary Supplements: Evaluating supplements, fact sheets, safety notices, internet health info
  5. United States Department of Agriculture (USDA) Food and Nutrition Information Center: General supplement and nutrition information, links to a variety of dietary supplement websites
  6. United States Pharmacopeia Dietary Supplement Verification Program: Independent testing of dietary supplements (human supplements only)

Disclaimer: Every effort has been made to ensure that the information contained in this article is current and correct. No responsibility is assumed by the publisher for loss or injury resulting from any use or operation of methods described herein. Because of rapid advances in medical sciences, independent verification of drug doses and recommendations should be made.

About the Author

Dr. Philip Judge

BVSc MVS PG Cert Vet Stud MACVSc (VECC; Medicine of Dogs)

Director: Vet Education Pty Ltd
Consultant in Veterinary Emergency and Critical Care
Internationally renowned lecturer and published author
Dedicated to providing you with innovative and exciting online learning!


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