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The Best Tumor-Fighting Foods for Pets

Chances are, if your dog or cat develops a tumor or other malignant condition, your vet may suggest feeding this soon-to-be-released pet food. Here's why following that advice may be a serious mistake, and what I recommend feeding instead, along with eight immune-enhancing add-ins.

tumor-fighting foods for pets


  • Cancer in dogs (in particular) and cats is as common as it is in humans; diet plays a pivotal role in both prevention and in helping pets live with the disease
  • While ultraprocessed pet food producers offer “prescription” and “therapeutic” diets presumably designed for pets with cancer, in my opinion, feeding these diets is a little like telling an ex-smoker with lung cancer to take up smoking again
  • If your dog or cat has cancer, it’s important to feed an anti-inflammatory, low glycemic diet of real, whole foods, along with beneficial add-ins and supplements

These days, cancer is as much a pet disease as it is a human disease, especially in dogs. An estimated 25% of canine companions will develop cancer during their lifetime, and the risk doubles to 50% for those older than 10. Cats have only a slight edge with a one in five (20%) chance of developing the disease.

According to pet food industry experts, owners of older dogs and cats are much more likely to buy “prescription” diets, and so, predictably, the ultraprocessed pet food manufacturer Hill’s Pet Nutrition is rising to the occasion with a soon-to-be-released “therapeutic” pet food marketed for dogs and cats with cancer.

“The formulation provides support that helps support pets’ daily activity, body condition, weight, and quality of life while they are living with cancer,” Karen Shenoy, DVM, U.S. chief veterinary officer of Hill’s Pet Nutrition told Petfood Industry.

The advertised goal of the new diet is to overcome the loss of appetite and weight loss typical of pets with cancer.

According to the manufacturer, ONC Care is “highly digestible with a very high energy density,” and is made with “Hill’s proprietary prebiotic formulation ActivBiome+ to help provide consistent stool quality.” In addition, “the dry kibble itself is softer, making it easier to chew,” and the “food also contains highly digestible protein to help maintain strength and energy, as well as added omega-3 fatty acids.”

How a Contributor to Pet Cancer Becomes a ‘Treatment’

As most of my regular bark & whiskers subscribers know, in my opinion, when it comes to the health of animal companions, ultraprocessed pet food is part of the problem and certainly not a solution to the epidemic of serious diseases seen in today’s dogs and cats.

So, with that thought in mind, I looked at the guaranteed analysis and ingredients in Hill’s new offering. Hill’s ONC Care Canine Dry guaranteed analysis and ingredients:

Hill’s ONC Care Canine Dry guaranteed analysis and ingredients
    Chicken, whole grain wheat, corn gluten meal, chicken fat, hydrolyzed chicken liver, soybean meal, brown rice, cracked pearled barley, egg product, chicken liver flavor, coconut oil, fish oil, ground pecan shells, pork liver flavor, lactic acid, calcium carbonate, potassium citrate, flaxseed, dried beet pulp, dried citrus pulp, carrots, iodized salt, DL-methionine, pressed cranberries, vitamins (vitamin E supplement, L-Ascorbyl-2-polyphosphate (source of vitamin c), niacin supplement, thiamine mononitrate, calcium pantothenate, vitamin A supplement, riboflavin supplement, biotin, pyridoxine hydrochloride, vitamin B12 supplement, folic acid, vitamin D3 supplement), choline chloride, L-tryptophan, natural flavors, minerals (ferrous sulfate, zinc oxide, copper sulfate, manganous oxide, calcium iodate, sodium selenite), taurine, mixed tocopherols for freshness, L-carnitine, beta-carotene

The diet boasts added carnitine that a) wouldn’t be needed if the formula contained more real meat, and b) is a negligible amount at less than 1% (suggesting it’s been added purely for marketing purposes).

The omega-3 fatty acids are also added in negligible (think “homeopathic”) amounts — not nearly sufficient for animals with massive inflammation from cancer. In addition, these essential fatty acids will certainly be oxidized after being high heat processed and sitting in a bag for extended periods.

And as if all that wasn’t enough, the diet contains countless advanced glycation end products (AGEs) and other carcinogens as a result of high-heat processing, and in term of macronutrients, is over 30% carbs (starch). Welcome to next level cancer care for pets?

Why Ultraprocessed Diets Are Bad News for Pets With Cancer

To help your animal companion avoid (or live with) cancer, it’s important to feed an anti-inflammatory (low starch) diet that resonates with their physiology. Dogs and cats don’t have a nutritional requirement for carbohydrates (starch), and it’s best to avoid feeding an abundance of any substance not required by the body, especially when fighting a sugar-loving disease, like cancer.

The more unnecessary and inappropriate the food (in this case, carbs), the more metabolic stress your pet must deal with.

Long term metabolic stress does a great deal of damage that revolves 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 to proliferate.

Cancer cells require the glucose in starchy foods to grow and multiply, so human nutritionists and most integrative and functional medicine veterinarians agree it’s wise to greatly reduce or eliminate cancer energy sources, including grains, legumes, fruits with fructose, and starchy, high glycemic vegetables like potatoes.

Keep in mind that 90% of dry pet food contains some form of potentially carcinogenic, highly processed starch. During the cooking process, carbohydrates interact with protein (the Maillard reaction) which in turn creates AGEs, which are known carcinogens. Even the novel “keto kibbles” have been extruded at high temperatures, creating byproducts that are burdensome for animals, especially those with cancer.

The correlation between consuming fast foods and cancer has been established in humans, 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 ultraprocessed, highly refined diets, and that feeding such diets to sick family members doesn’t provide their bodies with optimal fuel.

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. Ultraprocessed 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 processing steps 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.

Many of these diets are pasteurized (bacteria-free) 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:

  • Sprouts
  • Medicinal mushrooms
  • Turmeric/curcumin
  • Super green foods and brightly colored veggies
  • Decaf green tea
  • Fermented vegetables

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