Avoid This 'Expert' Oncology Advice for Your Pet

Analysis by Dr. Karen Shaw Becker

feeding pet with tumor

Story at-a-glance

  • If you’re looking for information on the best way to feed a pet with cancer, you may want to avoid advice from leading university veterinary colleges
  • Due to the established relationships between major pet food industry players and board-certified veterinary nutritionists, the latter has more than a passing interest in promoting only ultra-processed diets for both sick and healthy pets
  • To help your pet avoid cancer, it’s important to feed an anti-inflammatory, low glycemic diet of real, whole foods, along with beneficial add-ins and supplements
  • Other important steps you can take include carefully considering the timing of sterilization, especially in large breed dogs; keeping your animal companion lean and fit; and reducing exposure to toxins and unnecessary vaccines

We're living in a time right now in which finding factual, unbiased information on almost any subject has become difficult to impossible. Everywhere we turn and no matter our sources, we're bombarded with manipulated data that at the benign end of the spectrum is simply misleading, and at the other end, is potentially dangerous propaganda. It's an appalling situation that affects every aspect of our lives, and sadly, the lives of our animal companions as well.

The Mission: Warn Owners of Sick Pets Away From Fresh Diets

One pet-related example of, shall we say, ambiguous information appears in the "Petfoodology" section of the esteemed Tufts University Cummings Veterinary Medical Center Clinical Nutrition Service website. Petfoodology is hosted by a Clinical Nutrition Team consisting of three board-certified veterinary nutritionists who are faculty members at Cummings.

In 2017, the Clinical Nutrition Team posted an article titled "Feeding pets with cancer".1 My guess is that most pet parents and veterinarians researching this topic would be looking for guidance on recommended diets for pets with cancer, or at a minimum, types of food they definitely should, and should not be eating.

Sadly, the Clinical Nutrition Team's article will be of little use to them. In the second paragraph the authors launch into a diatribe against information found in "media and the Internet" that is, in their view, contradictory and confusing. Then they immediately admit that science-based information on the best nutrition for pets and people with cancer is minimal.

"Unfortunately, our knowledge of ideal nutritional modification during cancer treatment for pets (and people) is still small and while many recommendations can be commonly found, there is little scientific proof supporting them," the team writes.

However, this lack of knowledge and scientific proof doesn't stop them from putting their collective finger on the scale in support of ultra-processed pet food. Here's a screenshot of what pops up if you Google "should I change my pet's diet if they have cancer:"

google screenshot pet diet cancer

This statement summarizes these nutritionists' viewpoints quite succinctly: what you feed your pet with cancer doesn't matter, as long as it meets AAFCO minimum nutrient requirements. I completely disagree. I believe the quality and source of calories and nutrients matters greatly to overall health, contributing to health or disease potential. And food choices are especially important when addressing serious disease states such as cancer.

While I'm saddened that more board-certified veterinary nutritionists don't believe in the power of nutrition relating to disease potential and using food as medicine, this trend is also visible in human healthcare. Many human doctors don't correlate diet and lifestyle to their diagnoses or implement nutritional strategies as adjunctive tools in improving overall health or treating disease.

This is when it's important you align yourself with doctors (both MDs and veterinarians) that share your viewpoints on using food as medicine. By choosing healthcare practitioners that understand the importance of whole food nutrition, you'll decrease your frustration trying to explain your belief that food choices matter and you'll reduce their frustration in trying to talk you out of this approach.

Rather than argue, change doctors. There are many doctors and nutritionists who are passionate about using real food as real medicine: align with them.

Their Message: Only Ultra-Processed Pet Food Is Safe

After acknowledging the scarcity of research on diets for pets with cancer, the team goes on to make several assertions that not only aren't backed by science, but also seem to reveal an agenda.

"Adding more meat and other foods from your kitchen to your pet's normal food or starting to make your pet's food at home can lead to nutrient deficiencies that can make it harder for your pet to fight the cancer."

"The challenge with home-cooked diets is that unless they are carefully designed, nutrient deficiencies are common. We investigated the nutritional adequacy of home-cooked diet recipes for dogs from the Internet and books and found none of the 27 diets recommended for dogs with cancer met the minimum nutrient requirements that are required for a commercial diet for healthy dogs!"

"Some sources strongly recommend raw diets for pets with cancer but these diets could be very dangerous to your pet! It is very important to avoid feeding raw diets or treats to pets with cancer!"

"Low carbohydrate diets are commonly recommended because cancer cells rely on sugar as an energy source and in theory, a low carbohydrate diet will decrease the supply of sugar and "starve" the cancer.

While this is true in a test tube, improved survival or remission duration for pets being fed low carbohydrate diets has yet to be proven in dogs or cats. Similarly, there is also no proof to support the commonly repeated belief that grains are worse for cancer than other sources of carbohydrates."

The messaging here couldn't be clearer: home-cooked pet diets are dangerous, raw diets are downright deadly, and ultra-processed "fast food" diets are just fine for cats and dogs afflicted with serious health challenges.

Certainly, these nutritionists don't rely solely on meal replacement bars or all-in-one shakes to meet their own nutritional requirements; they eat some homemade food. I find it somewhat insulting that they insinuate pet parents are incapable of following instructions for preparing nutritionally complete recipes at home.

Sure, some uneducated owners do it wrong (as they point out), but what they didn't acknowledge is the vast majority of pet parents are fully capable and willing to follow balanced recipes to dramatically improve their pet's nutritional status by switching to ingredients they can control and prepare at home.

They also appear to be raw food-illiterate; they either don't know or fail to acknowledge that nearly half of all commercially available raw pet foods are sterile, as in devoid of all bacteria. This makes these raw food diets the safest foods on the market. Additionally, all raw food companies are required, by law, to adhere to the "zero tolerance" policy for salmonella.

There are many safe, exceptionally nutritious raw and gently cooked fresh food diets on the market, made with organic human grade ingredients (kibble is made with questionable feed grade ingredients). It appears this strong attempt to dissuade people from feeding substantially better quality, more species-appropriate fresh, real, whole foods to pets with cancer may be more political than nutritionally rational.

The Messengers and Potential Conflicts of Interest

There's a page in the Petfoodology site titled "Who we are and why you can trust us" that outlines the education and background of the three veterinarians, Lisa M. Freeman, DVM, PhD, DACVN, Cailin R. Heinze, VMD, MS, DACVN, and Deborah E. Linder, DVM, MS, DACVN) who comprise the Clinical Nutrition Team. From that page:

"We'll be straight with you — we are not employees of any pet food companies and we don't have any ownership interest in any companies that make pet food, treats, or supplements. Our goal isn't to sell you anything — we just want to answer your questions about feeding your pet, and help you find a feeding program that works for both of you.

We want this site to be the first place you look for reliable information on how to feed your pet — we designed it to answer many of the questions that pet owners ask us every day and we plan to keep adding to it so it stays current and continues to be a great resource for caring pet owners."2

However, scroll to the bottom of the page and you'll find this disclosure statement:

"Dr. Freeman has received research support from, given sponsored lectures for, or provided professional services to Aratana Therapeutics, Hill's Pet Nutrition, Nestlé Purina PetCare, and Royal Canin.

Dr. Heinze has done consulting for Lafeber and WellPet, given sponsored talks for Nestlé Purina PetCare and the Pet Food Institute; and provided professional services to Balance IT.com and Mark Morris Institute.

Dr. Linder has received speaker fees or research funding from Hill's Pet Nutrition, Nestlé Purina PetCare, and Royal Canin, and has provided professional services for Mark Morris Institute."

While Freeman, Heinze and Linder may not be employees of or have ownership interest in any pet food companies, they certainly have significant professional relationships with several and have received speaker/lecture and consultant fees, as well as research funding from them. There are mutually beneficial relationships occurring.

As I've noted in several past articles here at Mercola Healthy Pets, these types of arrangements between nutrition departments and the biggest players in the ultra-processed pet food industry are the rule rather than the exception.

Collectively, board-certified veterinary nutritionists remain the one group of health care professionals that advocate feeding a lifetime of ultra-processed foods and dissuade their clients from feeding fresh, real food. Human doctors and nutritionists recommend the opposite: they recommend reducing your intake of fast food and eating more real food.

The fresh food market is one of the fastest growing segments of the pet food industry and thankfully, the number of veterinary nutritionists supporting the feeding of fresh food diets is growing rapidly, but my guess is nutrition departments funded by Big Pet Food will be the last to acknowledge the health benefits of real food unless the pet food companies supporting these departments begin producing fresh food products that can compete in the marketplace.

Arguments Against Ultra-Processed Diets for Pets With Cancer

To help your animal companion avoid cancer, it's important to feed an anti-inflammatory diet that resonates with your animal's physiology. Dogs and cats don't have a nutritional requirement for carbohydrates (starch), so it's best to not feed an abundance of any substance not required by the body. The more unnecessary and inappropriate food you feed to your dog or cat (in this case, carbs) the more metabolic stress they will have.

Long term metabolic stress does a lot of damaging things to your pet's body that revolve around inflammation. Anything that creates or promotes inflammation in the body increases the risk for cancer. Current research suggests cancer is actually a metabolic disease rooted in chronic inflammation, fueled by carbohydrates (aka sugar). The inflammatory process ultimately creates a diseased environment that alters DNA and allows abnormal cells proliferate.

Cancer cells require the glucose in starches to grow and multiply, so human nutritionists and most integrative and functional medicine vets agree it's wise to eliminate that cancer energy source. Carbs to remove from your pet's diet include grains, legumes, fruits with fructose, and starchy, high glycemic vegetables like potatoes.

Keep in mind that 90% of dry pet food ("fast food") contains some form of potentially carcinogenic, highly processed starch. During the cooking process, carbohydrates interact with protein (the Maillard reaction) which in turn create advanced glycation end products (AGEs) which are known carcinogens. Even the novel "keto kibbles" have been extruded at high temperatures, creating these by-products that are one more burden for animals trying to avoid or address cancer.

The correlation between consuming fast foods and cancer has been established in humans,3 and my advice mirrors that of human nutritionists: incorporate as much fresh, unprocessed, "real" food into your entire family's diet as you can afford. Common sense tells us we shouldn't raise any of our family members solely on ultra-processed, highly refined diets and that continuing to feed ultra-processed diets to sick family members doesn't fuel their body optimally.

CANWI (the non-profit research organization I co-founded to conduct unbiased university-based pet food research) funded the first study of its kind evaluating the levels of AGEs in raw, canned and kibble diets. The results will be published in the upcoming months and will definitely get the pet food industry buzzing about role of food processing techniques and their influence on long-term health status.

Other sources of toxic contaminants that interfere with your pet's immunologic and metabolic wellbeing are often found in canned and kibble food, including heavy metals, glyphosate residues and mycotoxins.

Cancer cells generally can't use dietary fats for energy, so high amounts of good quality, unrefined (unheated) fats are nutritionally beneficial for pets fighting cancer, along with a reduced amount of protein and minimal starch. KetoPet Sanctuary trialed the use of raw ketogenic diets as an adjunctive therapy for canine neoplasia with good success and since then many companies have produced fresh food diets designed for dogs with cancer.

Another major contributor to inflammatory conditions is a diet too high in omega-6 fatty acids and too low in omega-3s. Omega-6s increase inflammation while the omega-3s do the reverse. Ultra-processed pet food is typically loaded with omega-6 fatty acids and deficient in clean sources of ocean-derived omega-3s that make it through the high-heat required to produce dry and canned food.

My Dietary Recommendations for Pets With Cancer

A healthy diet for your animal companion — one that is anti-inflammatory and not metabolically stressful — consists of real, whole foods, preferably raw (remember many are sterile!) or gently cooked.

It should include high-quality protein (muscle meat and organs), high amounts of unprocessed fat, EPA and DHA (omega-3 fatty acids) and low glycemic, brightly colored veggies that provide important antioxidants, fiber and polyphenols not found in meat. The proportions of these macronutrients can be tailored to meet the individual needs of the animal.

It's critical that your pet's diet is nutritionally balanced to not just meet minimal nutrient requirements, but include optimal levels of vitamins and minerals coming from real food (including vitamins D, E, A, and zinc and selenium), which means if you are preparing your pet's food at home you need to follow a recipe that ensures nutritional adequacy (this means nutrient information is provided with the recipe, ask your vet to double check if you're not sure if the recipe you're following is balanced). Don't guess.

Certain supplements and add-ins can also be very beneficial to enhance immune function, including:


Super green foods

Medicinal mushrooms

Decaf green tea

Digestive enzymes

Broccoli and blueberries


Fermented vegetables

Additional Steps You Can Take to Help Your Pet Avoid Cancer

If your pet is a large or giant breed dog, hold off neutering or spaying until the age of 18 months to 2 years — Studies have linked spaying and neutering to increasing cancer rates in dogs. Even better, investigate alternative ways to sterilize your pet without upsetting his or her important hormone balance.

Don't allow her to become overweight — Studies show that restricting the number of calories an animal eats prevents and/or delays the progression of tumor development across species. Fewer calories cause the cells of the body to block tumor growth, whereas too many calories can lead to obesity, and obesity is closely linked to increased cancer risk in humans.

There is a connection between too much glucose, increased insulin sensitivity, inflammation, and oxidative stress — all factors in obesity — and cancer. It's important to remember that fat doesn't just sit on your pet's body harmlessly. It produces inflammation that can promote tumor development.

Reduce or eliminate his exposure to toxins — These include chemical pesticides like flea and tick preventives, lawn chemicals (weed killers, herbicides, etc.), tobacco smoke, flame-retardants, household cleaners, and air scenting products like candles and plug-ins. Because we live in a toxic world and avoiding all chemical exposure is nearly impossible, I also suggest offering a periodic detoxification protocol to your pet.

Refuse unnecessary vaccinations — Vaccine protocols should be tailored to minimize risk and maximize protection, taking into account the breed, background, nutritional status, lifestyle, and overall vitality of the pet. Titer testing is a responsible way to ensure your furry family member has adequate immunity.