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THE WAR ON CANCER Part Three: Diet's Key Role

by Laura Weis

The first two articles in this three-part series examined the failing war on cancer, conventional therapies and the inherent genetic and biological Achilles' heel that renders our companion animals and us susceptible to cancer. While there are many therapies that can aid in reducing the risk of cancer or supporting our bodies during treatment, this article will focus on the biggest lever we can pull: the foods we feed our pets.

Western pets consume a diet that is frighteningly similar to the Standard American Diet (SAD). While wild canids, both modern and ancestral, eat a diet that is typically comprised of less than 5 percent carbohydrates, most American dogs and cats consume high levels of refined carbohydrates (often 55 percent of their diet or more) and excess calories, both of which produce hyperglycemia and hyperinsulinemia. These twin conditions are the most powerful drivers of inflammation, leading to cancer, degeneration and chronic disease. 

The mechanisms of this degenerative spiral are complex. Hyperglycemia (excess sugar) and caloric abundance signal our mitochondria to permit cellular reproduction as a constant possibility. Simultaneously, these same metabolic conditions, created by a profoundly unhealthy diet, injure vulnerable mitochondrial DNA and the electron transport chain, which creates damaging reactive oxygen species. A cascade of further changes can include turning on growth accelerator genes, decreasing the ability of the cell to differentiate, turning off growth suppressor genes and switching into permanent reproduction mode. Independent of these changes, persistent hyperglycemia causes increased levels of insulin-like growth factor 1 (IGF-1), which drives reproduction in cancer cells. When these changes, encouraged by a cancer-promoting diet, are combined with insults such as carcinogenic chemicals, radiation exposure, pathogens and other lifestyle hazards, rates of cancer climb.

While we cannot control every aspect of our pets’ lives, we can pull the biggest lever that can accelerate or reduce the risk of cancer: evolutionarily appropriate food and caloric restriction. Oncologists, both those who treat people and animals, are not trained in the cancer-preventing and cancer-reducing potential of food. We will focus on two powerful mechanisms that should be a mainstay of pet nutrition: the use of ketones as the “normal” fuel source, and consuming appropriate amounts of food to maintain a lean body mass. 


Ketones are water-soluble, energy-rich molecules that are naturally and normally produced by the body during periods of extreme exercise, during fasting or when the diet is comprised of higher amounts of fat, moderate amounts of protein and low amounts of carbohydrates. Ketones can also be produced in a pathological response during uncontrolled diabetes, a dangerous condition known as ketoacidosis that occurs in the absence of insulin.

The healthy mitochondria of most tissues use ketones as a clean and efficient fuel source, and ketones can pass through the blood-brain barrier to supply energy to the brain. In fact, ketones are neuro-protective and neuro-restorative, and are increasingly used in human medicine to combat diseases such as epilepsy, Alzheimer’s disease and other neuro-degenerative conditions. 

Ketones vs. Carbohydrates

Conventional nutrition has taught that ketones were the fallback mechanism for energy during periods of extreme starvation. But is this true? Ketones appeared very early in mammalian evolution as an energy source, and we know that the common ancestors of dogs, cats and humans relied on a diet high in fat and protein, with very little inclusion of carbohydrates. In fact, eating carbohydrates, which were very different from today’s easily consumed grains and starchy plants, likely occurred only episodically and seasonally, such as with a berry harvest, or when fat- and protein-rich foods were not available. 

    For humans, the starchy tubers and other sources of carbohydrate-rich energy of thousands of years ago required extensive processing to render the calories accessible and safe. Ancestral canids and felids accessed carbohydrates through the ingesta of their prey. Given this evolutionary picture, it is likely that the use of ketones was the default energy pattern for our ancestors and the ancestors of our pets, and the occasional consumption of large amounts of carbohydrates was rare. 

Diets that promote metabolic flexibility, with the default use of ketones as the primary fuel source, are cancer-preventing and can be extremely beneficial in treating cancer. Glucose is the primary fuel source used by cancer cells, as their damaged mitochondria cannot effectively use ketones for energy production. Calorie restriction and a ketogenic diet can help to treat primary tumors and metastatic disease, and can also help to support healthy cells during standard cancer therapies such as chemotherapy and radiation.

We will never eliminate cancer. Healthy pets and people have cancer cells; the production of these cells was a by-product of evolutionary compromises agreed upon billions of years ago. The question we must address is whether controlling and eliminating these cells will be a normal part of metabolic functioning, or whether the diet we provide our pets will encourage the production of cancer. The outcome of the Standard American Diet is disastrous, with accelerating rates of cancer and all chronic diseases. Our pets deserve better. 

Dr. Laura Weis and her husband, Dr. Ransome Weis, own and operate Doylestown Veterinary Hospital & Holistic Pet Care, and Holiday House Pet Resort & Training Center, in Doylestown. She focuses on homeopathy and nutrition counseling for her clients within the full-service veterinary practice. Call 215-345-6000 to request an appointment. 

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