Nutrition is always important in helping a sick pet get better, and it can be an essential element of care for cancer patients and for pets recovering from debilitating illnesses or surgery. Cancer and its treatments may alter the body’s ability to tolerate particular foods or use certain nutrients; moreover, clients often have a firm belief in nutrition as good medicine and may ask about or even insist on special diets or supplements for pets undergoing cancer treatments or otherwise in need of tender loving care. When a pet is diagnosed with cancer or faces a long recovery period, it’s an opportunity to team with clients to ensure optimal calorie intake and nourishing sustenance during treatment and healing. Here’s what to know about the latest research into diets for oncology patients and communicating with clients about a pet’s nutritional needs. Current research Contrary to what clients may have found through Google, it can be disappointing to them to learn little evidence is available that a particular type of diet is linked to development of cancer or that changing the diet of a pet who has been diagnosed with cancer will have a survival benefit. “There is an abundance of recommendations out there—low-carb, high-protein, raw, ketogenic—but there’s no actual in-the-dog data that ‘We tested this theory and this was proven to increase survival,’” said Cailin R. Heinze, VMD, DACVN, assistant professor of nutrition at Cummings School of Veterinary Medicine at Tufts University. “I think that’s a big challenge because a lot of pet owners read on the internet about these cancer-cure diets and then they get disillusioned when they come to their oncologist or they come to me or one of my colleagues and we say, ‘Actually, there’s no evidence diet makes a big difference in cancer.’” What researchers have found is that diet may help support canine cancer patients through treatment and recovery. Investigators at Colorado State University monitored canine cancer patients, looking at body-weight ratios, percentages of body fat and lean muscle mass, protein contents, the benefits of fatty acids and fiber, patterns in metabolic rates, eating habits, and more. In some cases, they found foods containing relatively low amounts of simple carbohydrates, moderate amounts of good-quality proteins and soluble and insoluble fiber, and moderate amounts of fats could help reduce or eliminate some of the metabolic changes that occurred with cancer cachexia. In other research, Dr. Heinze and her colleagues looked at whether a pet’s body condition—underweight, overweight, or normal—affected prognosis in certain cancers. Separate studies looked at various markers of metabolism in dogs with cancer versus healthy dogs, as well as whether diet could influence quality of life, if not survival. Some of the latter data was presented at the American College of Veterinary Internal Medicine Forum this year. “We found there was some suggestion in our trial that potentially diet may be able to do that,” Heinze said. In the case of cats, little to no research has been done on the relationship between diet and cancer treatment. In part, that’s probably because cats are less likely to receive treatment for cancer. What is known is that cats with cancer are more likely to be underweight, so they tend to have more muscle wasting and more weight loss than dogs. “It’s actually not that common for dogs to get super-emaciated with cancer,” Heinze said. “There aren’t many types of cancer that are very common in dogs where you actually get wasting. Cats are more likely to get wasting with cancer and so that may affect their prognosis.” Despite the overall lack of information, foods are available to help provide nutritional support for pets with cancer. Those diets may help improve quality and length of life for some cancer patients. The role of supplements Owners often want to give supplements to pets with cancer in hopes they will help support the immune system. In general, certain supplements probably won’t hurt and may help. Fish oil and mushroom extracts are backed by the most solid data, although not necessarily in dogs and cats. The evidence for fish oil is interesting, with a number of studies in humans and in rodent models, as well as one controversial study in dogs, said Cailin R. Heinze, VMD, DACVN, assistant professor of nutrition at Cummings School of Veterinary Medicine at Tufts University. As far as efficacy, it’s in no way comparable to chemotherapy or radiation or surgery, and it’s unlikely to provide a survival benefit, but it may have more subtle effects on a pet’s well-being. “I think fish oil is a very reasonable thing to supplement if your pet tolerates it,” Dr. Heinze said. “We can’t tell you exactly how much is ideal, but certainly it’s something that is reasonable to try.” Advise clients that some pets may have gastrointestinal side effects from too much fish oil. Others may experience effects on blood clotting, depending on the medication they’re taking. Some studies in rodent models have shown decreased immunity with high doses. The evidence is similar for mushrooms, which have been used in traditional medicine in China and elsewhere for as long as people have been around. A few studies have been done on the effects of mushroom extracts for treating cancer in dogs, and the results have not been dramatic. One of the biggest drawbacks is expense. For example, one of the more common products used in one study could cost several hundred dollars a month for a large dog, Heinze said. “You run into the question of not only is it unclear how much of a difference it actually makes, but it’s also very expensive,” she said. “But in general, if people want to use supplements, I would say fish oil and mushroom extracts are probably the ones I think have the most data behind them. There’s a ton of other supplements out there that are advertised for pets with cancer, but I think the data to support them is significantly weaker.” What pets need The ability to absorb nutrients and maintain a healthy weight is essential to fighting cancer effectively, as well as to maintaining quality of life. During treatment, animals may experience cancer cachexia, especially if they are on a chemotherapy or radiation regimen. Cancer-related changes in metabolism can cause decreased appetite, leading to reduced response to treatment and a greater likelihood of side effects associated with chemotherapy, radiation therapy, and surgery. The result can be shorter survival time. This is one of the areas where you can work with clients to optimize caloric intake. Meeting cancer patient energy needs is important to ensure they don’t lose muscle or excess weight, which can decrease their body’s ability to fight the disease. A diet with high energy density can help them maintain a healthy weight. Nutritional recommendations also may vary depending on the type of cancer. For instance, if the cancer is targeting a specific organ, such as the kidneys, a therapeutic diet designed for kidney disease may be the best choice. For dogs who may have a fat intolerance, use low-carbohydrate, high-fat diets with caution. Dogs with a history of pancreatitis should not be fed a low-carbohydrate diet. Talk to clients about what their pets eat and explain what is known and unknown about the effects of diet on cancer. If they are feeding a diet that is not complete or balanced or giving the pet too many treats, help them transition the animal to a higher quality food. Beyond that, with some exceptions, you can leave the choice of food up to the owner. Some owners choose to feed a diet low in carbohydrates, even though that has not been shown to make a difference in survival, Heinze said. Others prefer to prepare a pet’s food themselves. It gives them an element of control because they are choosing the ingredients. Feeding a home-cooked diet also can be a bonding experience with the pet. Finally, a home-cooked diet may be an option for pets who aren’t eating well because they don’t feel good. “I just work with my clients to help them have the healthiest diet possible, however they want to approach it,” Heinze said. The primary goal in treating cancer patients is to make sure their diets are nutritionally complete and balanced and they’re getting enough calories, said Bruce Kornreich, DVM, PhD, DACVIM, associate director of the Cornell Feline Health Center at the Cornell University College of Veterinary Medicine. That can be problematic when owners want to prepare homemade diets for pets who are ill. Without expert formulation, homemade diets can be deficient in multiple essential nutrients. “Making a homemade diet is not trivial, and it really needs to be done in consultation with the veterinary nutritionist,” he said. Many pets with cancer are on drugs that suppress the immune system. Their diet should be one that doesn’t contribute to risk of illness. For that reason, veterinarians typically recommend against feeding a raw diet to pets with cancer. “If you have a patient that is immunocompromised because they’re receiving, for example, chemotherapeutic drugs for cancer, they’re going to be less able to fight off a bacterial infection in their GI tract, so feeding raw foods to a patient receiving chemotherapy could be a bad idea,” Kornreich said. Several commercial diets are available that meet nutritional strategies for supporting cancer patients. Recipes for homemade versions are also available from veterinary nutritionists. Diets for convalescent pets Pets recovering from a serious illness or traumatic injury may have special dietary needs. The type of diet recommended for a convalescent depends on the condition and can range from tube feeding to a specialized diet. Often, the pet’s normal diet suffices. Critical-care diets are palatable and digestible, are high in energy density, and have moderate to high levels of protein. These foods are designed to be made into a slurry that can be put down a feeding tube or fed to a willing pet through a syringe or in a bowl. When deciding whether this type of diet is appropriate, consider the patient’s condition, said Cailin R. Heinze, VMD, DACVN, assistant professor of nutrition at Cummings School of Veterinary Medicine at Tufts University. For instance, pets recovering from gastrointestinal surgery who will eat on their own may do best with highly digestible food designed for pets with gastrointestinal issues. Pets recovering from orthopedic surgery probably don’t need anything other than their normal food, although they should receive reduced amounts to prevent weight gain from decreased activity. Pets recovering from a bad case of pancreatitis will need a different diet than those recovering from being hit by a car. Dogs who turn up their noses at their regular food or a therapeutic diet may eagerly eat cat food, which often has a strong aroma and is high in protein, making it more palatable. If cat food is going to be fed longer term, however, it should be checked to make sure none of the nutrient levels exceed the maximums for dogs. “If they’re not eating well, then using one of the really high-calorie diets or even home cooking for a few days can certainly be done,” Dr. Heinze said. The future While diet may certainly have benefits for pets with cancer, there’s still much to learn. No specific nutritional requirements have been established for dogs or cats with cancer, and questions remain about the optimum quantities of each nutrient and the effects on different types of cancers. “People are working on it, and in the next few years, we may know a lot more, but right now there’s no evidence that any specific type of diet either prevents, causes, or cures cancer or even dramatically affects the progression in pets,” Heinze said. “I think we still have a lot to learn on how to optimize diet for cancer patients. We’re probably decades away from really being able to do that well, but there’s a lot of interest right now.”
