Cancer is a significant health challenge in veterinary practice, especially for cats and dogs. Oncology has become one of the most influential and studied areas in both human and companion animal health. Nutrition plays a crucial role in the management of oncology patients in veterinary medicine. Dogs with cancer have special nutritional needs. In human patients with cancer, it has been shown that malnutrition can increase the risk of complications from therapy and decrease survival times. Improved quality of life and improved response to therapy are observed in those with good nutritional status. Providing good nutrition to dogs with cancer is key to assuring they have the best response to therapy and the optimal quality of life. After a diagnosis of cancer has been confirmed, many pet owners seek nutritional advice in an effort to address the disease from another angle. It is not to be used to diagnose or treat any disease, and should not be used as a substitute for proper veterinary consultation and care.
Understanding Cancer Cachexia
The weight loss and loss of body condition associated with cancer is different than the weight loss seen in a dog who may be suffering from starvation. The weight loss seen in dogs with cancer is called “cancer cachexia.” Cachexia is characterized primarily by loss of muscle mass and is a common and serious syndrome in cancer patients. For companion animals, the frequency of muscle loss related to neoplastic diagnoses is substantial. Dogs and cats with cancer-associated cachexia present reduced quality of life, response to treatment and a lower rate of disease remission when compared to patients who do not exhibit cachexia.
During starvation, an animal first loses body fat. In cancer cachexia, the animal loses both fat and muscle at an equal rate. It results not only from reduced caloric intake, but from complex metabolic changes induced by cancer, which lead to the degradation of muscle and adipose tissue. Early identification of this syndrome is challenging, but essential for effective management.
Among the commonly reported first signs are anorexia, loss of appetite, fatigue, low immunity, and weight loss, which often appear before the decline in muscle mass becomes clinically apparent. The weight reduction due to cachexia does not occur simply due to a negative caloric balance, which normally result in fat utilization as metabolic fuel. In dogs and cats affected by cancer, there is an increase in the plasma concentration of inflammatory mediators, including inflammatory catecholamines and cytokines, along with stress-related hormones such as cortisol, insulin, and glucagon, which interfere with the ability to use fat as the main energy source. Thus, to meet basal energy needs metabolism resorts to available amino acids, rapidly catabolizing muscle reserves.
Consequently, the loss of lean mass is a hallmark of cachexia, already identifiable in early clinical stages. The metabolic changes caused by cancer also influence glucose utilization. Neoplasia consumes glucose to generate energy through anaerobic metabolism, resulting in lactate as the final product and promoting an acidic environment that favors tumor growth. The reconversion of lactate to glucose via the Cori cycle is the animal organism’s response, to prevent acidification of the environment.
Read also: Canine Kidney Diet: Ingredient Breakdown
Identifying lean mass reduction remains a challenge in veterinary medicine, especially in the early stages of the syndrome, due to the lower detectability of signs. Therefore, diagnosing cachexia solely based on weight loss can lead to underdiagnosis and consequently errors in the treatment of the already debilitated patient. The use of frequent body condition assessment and more sophisticated techniques, such as dual-energy X-ray absorptiometry (DEXA) and bioimpedance analysis, although still having limitations, allows for better accuracy when diagnosing.
Factors Affecting Appetite in Dogs with Cancer
Among the many difficulties in the nutritional management of cancer patients, alleviating the effects of cancer on appetite is one of the main focuses to bring any remaining possibility of cure or quality of life. Loss of appetite is also one of the main causes of pet owners’ concern, since this is one of the few variables that he is able to interfere within the day-to-day care, and it is associated with their interpretation of health and well-being. Inappetence in dogs and cats with cancer is multifactorial and may be primarily related to the disease or drug treatment and its adverse effects. The overall hunger and satiety signaling rely on the perception that food has reached the gastrointestinal tract and glucose has entered the cells.
Direct Effects of the Tumor
Some tumors, because of their location in the mouth, throat or intestinal tract may make eating, swallowing, or the digestion of food difficult.
Chemotherapy
Drugs used in chemotherapy can alter the sense of smell or taste, which leads to a decrease in interest in food. They can also cause nausea and even vomiting and diarrhea. In some cases, dogs can develop a food aversion.
Radiation Therapy
Radiation affects not only the tumor, but normal areas of tissue around the tumor. Radiation of the head or neck can cause changes in the production of saliva which makes eating and swallowing difficult. It can also cause inflammation of the mouth, tongue and esophagus.
Read also: Overview of Metabolic Diets in Cancer Research
Changes in Metabolism
Cancer can change the body’s metabolism. Cancer cells prefer to use simple carbohydrates like glucose as energy. They use a different pathway than normal cells, however, so the body needs to use even more calories to metabolize the breakdown products produced by the cancer cells.
Body’s Response to the Cancer
The body can produce substances in response to the cancer. Cytokines such as IL-1, IL-6 and TNF-α play central roles in orexia regulation, often promoting anorexia by activating mechanisms that inhibit appetite. IL-1 is a cytokine primarily known for its role in the immune system and has gained attention due to its effects on appetite regulation. IL-6 is produced by T cells and adipocytes, and increases gradually during the early stages of cachexia, rising dramatically before death. TNF-α is primarily produced by activated macrophages, although it can be secreted by many other cell types, including adipocytes, endothelial cells, and certain immune cells.
Besides these cytokines, some emerging signaling mediators are gaining some focus in the anorexia-cachexia syndrome of cancer. In a review by Talbert et al. Activin A and GDF-15 are produced by some type of tumors and are believed to regulate feeding in humans and were described in cases of pancreatic and other solid tumors. Finally, lipocalin-2 is another factor produced by tumors and have been described in human patients with pancreatic cancer.
Nutritional Strategies for Dogs with Cancer
Carefully formulated diets that limit the energy available to cancer while maintaining the patient’s needs and promoting anti-inflammatory and immunomodulatory effects, can improve the quality of life and prolong the survival of affected animals.
Macronutrient Composition
As it is a multifactorial syndrome, simplistic suggestions regarding preventive treatment methods are uncertain in terms of results. The use of foods that prevent energy supply to the tumor but meet the patient’s needs is considered ideal.
Read also: The Hoxsey Diet
- Energy Dense: In general, foods with a higher caloric content are preferred. If your pet is not eating well, you should offer an energy dense diet that he/she likes. Feeding enough calories is the most important means to address nutritional concerns. Providing a palatable diet that your pet will eat consistently is more important than providing a specialized diet. There are a few highly palatable, energy dense, ‘recovery diets’ that your dog may like including Hill’s Prescription Diet a/d, Iams Maximum Calorie, or Royal Canin Recovery RS. Other diets that may be considered include canned or dry kitten/ puppy foods and diets for active dogs.
- High in fat: Tumor cells are much less likely to use fat for energy, whereas the dog’s normal cells find fats an excellent source. At one point, diets with low carbohydrate level and high lipid content were thought to be the best strategy, as it hinders the consumption of glucose by cancer cells and provides the necessary energy for metabolic functions by using fat as the main energy source.
- Moderately high in protein: Since cancer cachexia is associated with a decrease in muscle mass, and muscle is high in protein, moderately high protein levels should be available to dogs with cancer, provided they have normal kidney and liver function. High protein content supports the maintenance and reconstruction of lean mass, which is compromised by the tumor’s amino acids catabolism. Adequate intake of proteins and specific amino acids, such as leucine and lysine, aids in maintaining lean mass and improving the immune response, which is particularly important for dogs and cats with cancer.
- Low in carbohydrates: Since tumor cells prefer carbohydrates, diets low in carbohydrates will theoretically give the tumor cells less to grow on. Later, other authors raised the hypothesis that the carbohydrate intake was not the main concern, but the glycemic index of these. A higher glycemic index can stimulate the overload production of insulin that leads to the secretion of anabolic hormones such as insulin-like growth factor type 1 (IGF-1) and growth hormone (GH), whose receptors are overexpressed by many tumors.
Fortified Nutrients
Some dog foods are fortified with certain nutrients that can be beneficial to dogs with cancer. Nutraceutical addition to the diet of oncology patients is also encouraged, and can promote anti-inflammatory and immunomodulatory effects.
- Omega-3 fatty acids: Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are omega-3 fatty acids found in fish oils. They may be very beneficial to dogs with cancer. It not only reduces cachexia, it may also have a direct effect on the tumor cells themselves. Omega-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid, serve as natural anti-inflammatories in cells by inhibiting cyclooxygenase. There is evidence in cancer patients that these fatty acids can help prevent or reverse cancer cachexia, especially in people with gastrointestinal cancers. Omega-3 fatty acids also may be able to kill cancer directly and have been shown to reduce cellular proliferation, angiogenesis and invasion, and increase programmed cell death. Since some dog foods already contain increased amounts of omega-3 fatty acids, it is best to consult with your veterinarian before supplementing.
- Arginine: Arginine is an important amino acid for dogs. Arginine can benefit the immune system and may influence tumor growth. Although the optimal amount of arginine for dogs with cancer has not been determined, a level of 2% of dry matter or higher is generally recommended.
- Antioxidants: There remains some controversy as to whether antioxidants should be given to dogs with cancer. Although they can be helpful, they may also alter the effectiveness of certain cancer therapies.
Encouraging Eating
We can choose the appropriate food to feed a dog with cancer but that is only half of the battle. We also have to make sure the dog will eat it. Identifying and treating appetite loss is crucial for the success of nutritional management, and encouragement for the patient to eat should be provided by both owners and veterinarians. Implementing adjustments to the diet, nutritional support, or other nutritional approaches generally brings benefits in promoting food intake and improving the quality of life of these animals.
- Increasing the moisture: For dogs who prefer foods with higher moisture, switch to a canned food or add water to the dry kibble.
- Increasing the aroma: Warming canned food to body temperature can help increase the aroma of the food. If heating in a microwave, be very careful to mix it well afterwards to avoid any hot spots. Only warm the food to body temperature (around 100° F, not hotter).
- Assuring freshness: It is best to offer multiple small meals a day to assure the food is fresh.
- Adding flavorings to the food: Dogs like the taste of sweetness and salt. If advised by your veterinarian, these can be added in small amounts to the dog food.
- Avoiding the association of medications with food: Do not mix medications into food or water and it is best to not medicate immediately before or after a meal. Some medications need to be given with food, however, to avoid stomach upset.
- Making eating easy: Be sure the food bowls are easily accessible. You may want to place multiple bowls around the house. Be sure your dog can access the food.
- Avoiding feeding if the dog is nauseated: It is fine to try to hand feed your dog in an attempt to get her to eat. When a dog (or person) is nauseated, however, the last thing they want is food. Do not try to coax your dog to eat if she is obviously nauseated (drools at the sight of food, turns away, spits out food). This can lead to the development of food aversions.
- Administering appetite stimulants: There are several drugs which may stimulate the appetite in dogs. If a dog will not eat on her own, a feeding tube can be used until the dog starts to feel better. Feeding tubes are the best way to provide nutrition to dogs with cancer cachexia who will not eat on their own. The feeding tubes are generally tolerated very well by dogs and make giving food and administering medications quite simple.
Alternative Diets: Raw vs. Cooked
As noted on the main page for Canine Lymphoma Holistic Treatment page, many of the commercial dog foods on the market are filled with byproducts and fillers that are inexpensive but don’t fit our dogs’ nutritional needs - especially when our dogs have cancer. Cancer feeds off of the carbohydrates (grains, etc.) that are found in most dog foods, so your dog’s regular food may actually be causing the cancer to grow faster. Instead, we want to feed our dogs foods that contain a lot of protein (generally from meat, lots of meat).
Although there’s some controversy around it, especially for dogs who are currently undergoing chemotherapy treatments - many holistic vets recommend a “raw meat diet” for most of their Canine Lymphoma patients. Veterinarians who oppose feeding raw meat to dogs with cancer, worry that their weakened immune system may make them susceptible to food poisoning or other disease as a result of eating these raw meats. And if that is a concern for you, then the general recommendation is to cook the meat slightly, to remove possible disease, but minimize the cooking to the extent you feel comfortable to avoid cooking away many of the nutrients that are available to dogs from eating their meat raw.
Although you can’t feed a dog straight meat alone (like us, they need a more balanced diet that includes vegetables and other vitamins as well), raw meat recipes are specifically designed to meet dogs’ nutritional needs. You can buy quality, pre-made, raw meat packages at most holistic pet shops, or you can make the recipe yourself. If you wish to cook for your pet, a customized approach is best so that your pet’s individual needs are met.
Raw pet diets are increasingly popular in some areas and are sometimes recommended by veterinarians. Proponents proclaim many health benefits associated with raw diets, and may state that canned and kibble commercial diets are harmful. However, despite these claims, there remains no scientific support for any of the proposed benefits, or to suggest that kibble and canned are harmful. Overall, there have been no studies that demonstrate any long-term health benefits of raw diets compared to other types of pet food. On the other hand, there are documented risks of raw diets. The primary concerns are nutritional adequacy (excesses and/or deficiencies in essential nutrients) and contamination with pathogenic microorganisms (bacteria and parasites).
It is an often-repeated myth that animals do not become sick when consuming diets contaminated with Salmonella or other pathogens. There are many documented incidences of pets becoming ill from contaminated diets. Additionally, pets who do not develop clinical illness when fed contaminated products still introduce a risk to humans and other pets in the environment through shedding of organisms in the feces and contamination of feeding bowls and surrounding environment. Feeding of raw diets is a documented risk factor for fecal shedding of Salmonella, E. coli, and Campylobacter in healthy dogs.
Given the lack of any documented nutritional advantages and the strongly documented risks, we do not recommend feeding raw diets to dogs and cats. Any of the associated benefits, such as decreased stool volume, high palatability, control over ingredients, and others, can be safely achieved with the use of a properly formulated, balanced, home-cooked diet.
Superfoods for Dogs with Cancer
Just as healthy food choices can reduce our risk of getting cancer, giving cancer-fighting foods to your dog may prove life-saving in the long run. Here’s a list of superfoods for dogs that you can include in their diet to boost health and help to prevent cancer or minimize its effects:
- Broccoli: Broccoli is referred to as a superfood because it’s chock full of fiber and important nutrients including calcium, potassium, protein, beta-carotene, and vitamin C, as well as vitamins A and D. It is rich in glucosinates, which break down into biologically active compounds that have anticancer properties. Lightly steaming these crucifers releases the cancer-fighting enzyme indole and makes them easier for your dog to digest.
- Sweet Potatoes: Rich in vitamins B6, C, E, and D, sweet potatoes are more powerful than we might think. They contain carotenoids and beta-carotene, which support vitamin A and this may be a key factor in reducing the risk of certain cancers. Cook or bake sweet potatoes until they are tender enough to eat. You can then cut them into small cubes or mash them for easier consumption before adding them to your dog’s bowl.
- Coconut Oil: Coconut Oil contains fatty acids and plant sterols that mimic blood cholesterol and may help to block the absorption of cholesterol in the body. In addition to its anti-tumor properties, coconut oil is known to be beneficial for the skin and may clear up precancerous lesions and protect against cancerous growths.
- Pumpkin: Pumpkin’s bright orange color is the visible signal that it is rich in beta-carotene, which is converted into Vitamin A within the body. Vitamin A is an antioxidant that is critical in cancer prevention because it prevents damage caused by free radicals.
- Beets: Full of nutrients, these vegetables are as healthy as they are tasty. They are rich in folic acid, potassium, and beta-carotene. They have a high, insoluble fiber content, which boosts the body’s detoxifying process and can help support healthy liver function.
- Fish and fish oil: Omega-3 is a fatty acid that shrinks tumors and reduces inflammation. Fish oil has tons of other benefits for your dog, and many owners add it to their pups’ food to help keep coats shiny and fight skin dryness. For dogs already diagnosed with cancer, fish oil can slow the growth of the disease and is often recommended as part of their treatment.
- Dark Berries - Blueberries & Blackberries: The dark pigments or anthocyanins that give blueberries and blackberries their rich color have anti-inflammatory properties that are critical in cancer prevention and treatment.
- Pitted Fruits - Peaches and Plums: Peaches are high in antioxidants and work well to remove toxins from the body. Plums are equally rich in antioxidants and also contain vitamin C and iron.