Does Kibble Cause Cancer?

Over the weekend, there was a veterinary conference focusing on cancer, with a talk by a board certified veterinary nutritionist. Like a large number of her board certified colleagues, she is employed by a large pet food company.

She opened with remarks stating that there has never been a study that showed that eating a processed, extruded commercial food (AKA kibble or dry food) causes cancer. And I would agree with her — no one is going to be able to do such a study. We cannot put dogs in a vacuum, avoiding all the other things that we know pose a cancer risk, to evaluate the effect of a single variable such as diet on cancer incidence. And the cost of such a project, with a large number of dogs being monitored for ten or more years would be huge.

However, her statement was worded to exonerate kibble from any cancer blame, rather than thinking in a scientific manner and asking the question, “Could kibble have any role in the occurrence of cancer?” Of course, if one’s livelihood depends upon an industry that only produces ultra-processed extruded products from less than human quality ingredients, I can understand defending that product from any blame. However, dog owners deserve to know more, to have the information they need to make informed decisions that are right for them.

So, what are the risk factors for cancer posed by ultraprocessed kibble?

1. Cooking meats at high temperatures produces heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). Cooking some starches produces acrylamides. These have been shown to increase cancer risks in humans and rodents, which is expected to be true of dogs. See this fact sheet from the National Cancer Institute.
2. High carbohydrate (starch) levels, often between 40 and 50 percent, raise the dog’s blood sugar. Scientist Otto Warburg won a Nobel price in the 1930’s for his work showing cancer cells’ dependence on glucose for replication. This is one of the principles behind a ketogenic diet for the cancer patient, which keeps blood glucose low, effectively starving cancer cells while the rest of the body cells can use ketones for energy.
3. The combination of high carbohydrates, free-radicals, and low anti-oxidants as found in typical kibble may cause the dog’s body to work more aggressively to metabolise the food. This can cause metabolic stress and chronic inflammation, which makes for a higher risk environment for cancer to develop. Research at the University of Helsinki showed that dogs who were on a kibble diet had elevated levels of homocysteine – ten times higher versus those who ate a minimally processed diet. (PDF)

So, what feeding plan could potentially lower cancer risks?

Obviously, more gentle cooking is a common sense solution to PAHs, HCAs, and acrylamindes. Decreasing the amount of carbohydrates is not only helpful in moderating blood glucose levels, it also can make maintaining lean body weight easier. Veterinary oncologist Dr. Greg Ogilvie recommends a diet containing low amounts of simple carbohydrates, moderate protein and high-quality unsaturated fat as most effective for dog cancers in patients. Providing higher levels of omega 3 fatty acids compared to the inflammatory omega 6 fatty acids is helpful, as is adding in fresh food sources of antioxidants, including mushrooms, some berries, and even ginger.

I’m tired of dog owners being misled by food or pharmaceutical companies about the safety and/or efficacy of their products, by someone whose salary depends on that product selling. And I wish more dog owners would not blindly trust the contents of little brown nuggets to contain all that their dog needs fully nourish their bodies, every day, every meal. What do you think the implications of eating a typical breakfast cereal for every meal, from the time you were a child through adulthood, would be? Yet that is essentially what the kibble industry tells us to do for our dogs. Our dogs deserve better.