While many pet owners and veterinarians are interested in the interaction between diet and cancer, most current recommendations for the nutritional management of cancer in dogs and cats have limited evidence or are based on data taken from people. Nonetheless, a variety of websites and books offer strategies on what to feed a pet with cancer. In many cases, these diet plans are not complete and can lead to nutrient imbalances.

The primary nutritional focus for pet patients with cancer is to maintain healthy energy levels by meeting their calorie requirements. As a result, it is essential to feed your pet a complete and balanced diet to help them maintain body mass and avoid muscle atrophy. To best support your pet’s health during cancer treatment, modifications may only be appropriate if your pet shows reduced interest in food or if other medical conditions exist that warrant a change in diet.

A Closer Look at Common Recommendations

Supplementation of antioxidants is commonly recommended to avoid oxidative damage, which may lead to neoplastic transformation. However, once the cancer is already present, high antioxidant supplementation may be counter-productive as some of the therapeutic agents used to treat cancer act by causing oxidative damage to the cancer cells.

Polyunsaturated omega-3 fatty acids supplementation (EPA and DHA) has been recommended for people and dogs with cancer. This supplementation strategy is based on in vitro cell culture studies, rodent models, clinical trials in people with cancer, and clinical trials in dogs with lymphoma and nasal tumors. To date, an optimal dose has not been established. Care should be taken when introducing fish oil supplementation as it has been reported that dogs fed a high-fat diet supplemented with omega-3 fatty acids developed gastrointestinal responses.

Research indicates that dogs with cancer have alterations in carbohydrate metabolism. One strategy proposed is to limit dietary carbohydrates based on the premise that cancer cells can readily use carbohydrates as an energy source. In contrast, other sources of energy, such as fat and protein, are used less efficiently. More work is needed to determine whether a lower carbohydrate diet is beneficial to dogs and cats with cancer. When a diet is lower in carbohydrates, more of the calories are coming from fat or protein. Not all pets will tolerate a high-fat diet, and in cases where there are other medical conditions, a high protein or high-fat diet may not be advised.

As pet parents, we naturally want the very best for our companions, especially when they are sick. Before making any changes to your pet’s diet, we recommend speaking with your pet’s veterinary oncologist.

Dr. Camille Torres-Henderson is a veterinarian with the Clinical Veterinary Nutrition Service at Colorado State University’s James L. Voss Veterinary Teaching Hospital. She completed specialty training in nutrition and can offer a comprehensive review of your pet’s medical history, evaluation of the current diet, and recommendations for feeding your pet.