By Dr. Alison Book, DACVIM Oncology

March is right around the corner, which means it’s almost National Nutrition Month. In honor of this, we want to discuss nutrition and cancer over the next few weeks. In the first post, we will answer one of the most commonly asked questions, that is, what should I feed my dog or cat who has cancer?

Before getting started, it’s important to say that there is little scientific research to support any nutritional recommendation for pets with cancer. In other words, specific diets have NOT been proven to positively or negatively affect outcomes for dogs or cats with cancer. With that said, good nutrition and optimal body condition is important. Good body condition can improve quality of life and may improve your pet’s resilience during treatment and overall prognosis.

Is it normal for dogs or cats with cancer to lose weight?

There are several reasons why your pet could lose weight if it has cancer. Inadequate food intake is probably the most common. This may occur if the tumor’s location (usually in the gastrointestinal tract) is causing pain associated with eating or problems with normal food digestion and movement. Additionally, while most pets have a great quality of life during chemotherapy, but some could experience nausea or changes in taste or smell that could affect appetite during treatment.

A much less common reason for weight loss has to do with increases in energy requirements as a result of the tumor or systemic inflammation. This is rare in dogs but may occur in as many as 56% of cats with cancer.

What does cancer metabolism have to do with it?

Some studies have shown that cancer cells rely more heavily on glucose, a carbohydrate, and the metabolic process that generates glucose for energy production and growth.

So, we should be feeding a low carbohydrate diet to “starve the cancer”, right? Well, when dogs with lymphoma (a common cancer) were fed a diet that was either high or low in carbohydrates, no difference was seen in the remission or survival time between groups. Also, protein and fat can be converted to glucose by the body and so the amount available for tumor use probably remains constant. Thus, the use of low carbohydrate diets for this purpose is probably unwarranted for pets with cancer.

So what is the optimal nutrition plan for my dog or cat?

Developing an individual plan starts with providing an accurate picture of how much and what your dog or cat is eating (including treats, table food and supplements!). If you aren’t sure, we recommend a food diary. We will determine your pet’s body condition and watch weight trends to advise you about changes in caloric intake. With regards to dietary content, here are our general recommendations:

1. ‘DO NO HARM’: Sudden dietary changes can upset the balance of the gastrointestinal tract and lead to problems such as nausea or diarrhea. Therefore, any changes you do make for your pet should be done very slowly.

2. Feed a balanced, high quality diet. The ideal ranges (dry matter basis) are: Protein >30%, Fat >25%, Carbohydrate <25%

-Commercially available diets: Hill’s n/d, Purina JM, Hill’s J/D, prescription diabetic diets, other maintenance diets w/ similar nutrient content

-Home cooking:,,

3. Higher protein (>35% for cats and >30% for dogs): Higher protein diets may prevent lean muscle wasting (especially important in cats) and support gastrointestinal health. They may also provide higher levels of amino acids that have been shown to inhibit cancer growth like arginine (try for >2%).

4. Increased omega-3 fatty acids (try for >5%): These special fats may improve diet taste, decrease lean muscle loss, and potentially have anti-cancer effects. There is little downside to increasing omega-3 fatty acids in pets with cancer but the optimal dose for dogs and cats is still unknown. Please talk to your veterinary oncologist for recommendations.

5. Vitamins and supplements: stay tuned for part three.

What if my dog/cat is on a special diet for another disease?

Some dogs and cats cannot tolerate high protein diets due to concurrent diseases and have other special requirements. If your pet is already on a special diet for another disease (kidney, liver, heart etc.), we recommend continuing this unless directed otherwise.