Dog Food Logic – Make Smart Decisions on What You Feed Your Dog

The following is an excerpt adapted from a new book that can help you make smart decisions about what to feed your dog.


Two years ago, my friend Pam’s six-year-old Akita, Bruino, was diagnosed with bone cancer. Bruino had had his share of health issues during his short life; he was born to a rescued and severely malnourished and neglected mother, he developed several skeletal disorders before he was a year old, and he later required surgery to repair the cruciate ligament in his left knee. Still, throughout all of this, Bruino remained an easygoing and friendly fellow, getting along well with people and dogs and never quite seeming to realize that he greatly outweighed his owner and the majority of his canine friends.

When Bruino started to limp during a walk one day, Pam assumed that either the surgical repair to his knee had failed or that he was developing arthritis in that knee. Unfortunately, x-rays revealed the problem to be something much worse: a bone tumor located in his femur.

Dog Food Logic by Linda P. Case

We are fortunate that we live in a university town with a veterinary college and an excellent cancer-care clinic. Bruino was examined the next day by a team of board-certified veterinary oncologists. Information was presented to Pam about the disease, its prognosis, and several options for Bruino’s care.

Although amputation is frequently the treatment of choice with osteo-sarcoma, Bruino’s large size coupled with his mobility problems made him a poor candidate for this option. After consulting with the veterinary oncologists, the orthopedist who had performed Bruino’s knee surgery, her own veterinarian, and her training friends, Pam opted to provide Bruino with several palliative rounds of chemotherapy and also to enroll him in a clinical research trial that was testing the effects of a bone-salvaging drug for dogs with osteosarcoma. Pam and I also discussed Bruino’s diet, and she made some changes that were designed to support his body condition, reduce inflammation, and possibly slow tumor growth.

Bruino responded well to treatment. His pain and swelling were reduced, and his quality of life continued to be very good.

During this time, Pam was in contact via email with a number of dog folks whom she knew from being involved with Akita rescue. One acquaintance – we will call her “Jane” – took it upon herself to inform Pam via email that feeding Bruino a commercial diet during his young life had almost certainly led to his cancer. Further, this woman proclaimed, if Pam would just start to feed Bruino the homemade diet that she recommended, plus a concoction of nutritional supplements that she would provide, this would slow progression and could even cure his cancer.

Like most of us, Pam would do anything possible to help her beloved dog. She considered changing Bruino’s food and purchasing the packets of supplements. Pam trusted that this person was sincere in her claims. This was a known dog enthusiast who clearly believed in her own words and in the results that her prescribed diet and supplements could bring. (I would add that I like to think she never intended to be the source of the emotional pain that her words caused to Pam.)

After more thought, and more discussion with me and with Bruino’s team of veterinarians, Pam decided to stay with her planned course and declined to use the diet that Jane promoted. During our last discussion about this, Pam commented, “Well, if her diet works so well, wouldn’t there be studies showing that it worked, and wouldn’t more people be using it?”

Yes, indeed, that is certainly the right question to ask.

Mistakes Were Made…But Not Intentionally 

The woman foisting unsolicited food advice upon Pam was probably sincere (though arguably insensitive). She believed that feeding her homemade dog food and providing a nutrient supplement could prevent cancer from developing in healthy dogs and cure disease in diagnosed dogs. Most readers will agree that this is a pretty extravagant claim. Yet, she insisted with conviction, and Pam, in a state of emotional turmoil, considered giving it a try.

We all hear and read such claims in the popular press, on the Internet, or when talking to Joe next door (who happens to know a lot about dogs). Why is it that we, as supposedly the most intelligent species on the planet, are so susceptible to believing such claims and often make decisions in response to assertions that are accompanied by little or no supporting evidence? Why do we sometimes make a choice that seems to be a good idea (i.e., it feels right) but in reality has no actual evidence supporting its benefit or superiority?

In Chapter 1, I discussed how our emotions – important and essential as they are – not only influence our behavior but also frequently do so without our conscious awareness.
Additionally, our brains efficiently process information using a set of mental shortcuts called heuristics that enable us to rapidly observe a scene, extract meaning from it, and react in what is (usually) an appropriate manner. And, as with the emotional input, all of this mental work takes place beneath the surface of our consciousness. It is only the result of processing the incoming information (the action or reaction) that we are consciously aware of. It does not feel this way because we are also masters at “back-reasoning.” If asked why we made a particular decision or choice, we can immediately explain why.

However, at the time that the choice is made, functional MRI (fMRI) studies have shown that the processing is much too rapid to have allowed us to work through the series of logical steps to reach the choice – at least not consciously. Again, the benefits of this subconscious system are its processing speed and efficiency.

But with every benefit there is a cost. The price that we pay for rapid-fire analysis is that our brains miss details – details that may be essential in certain situations for reliable decision-making. And, just as with emotionally influenced choices, we are unaware of these missed details. Before reaching the conscious level of “Act now, do this!” our brains fill in a set of details for us, using our unique set of beliefs, experiences, and expectations.

For most processing and decision-making, this system works well because past patterns often accurately predict current patterns. However, the system is also biased by our opinions and beliefs, and so can make mistakes. As a set, these mistakes are referred to as cognitive biases, predictable patterns of thought and behavior that lead us to draw incorrect conclusions. Similar errors called logical fallacies refer to faulty arguments that lead to errors in logic – again, without our awareness – usually because we are highly invested in supporting a particular answer or solution.

Happily for us, psychologists, neuroscientists, and behaviorists have been studying these biases and fallacies for many years. Although we cannot completely prevent them (that subconscious mind thing again), we can be aware of the existence of these traps and their potential to lead us astray when making choices. Just as many of us are talented dog trainers, we can also become effective “mind trainers,” teaching ourselves to avoid or correct for these traps when making decisions for our dogs’ health (and for other important things in life).

Cognitive Bias & Logical Fallacies

The following are some specific types of cognitive biases and logical fallacies that may unduly influence us as we try to select foods, choose the best feeding approach, and make decisions for our dog’s nutritional well-being (each of these are discussed in more detail in the book):

Confirmation bias is the tendency to seek out and remember information that matches what we already believe, and to ignore or discount information that is not in agreement with our preformed views. As just one example, confirmation bias is at work when we become convinced that a dog’s itchy skin is caused by the chicken meal in her diet and then attend to only those signs that confirm this belief (itchy skin, commercial food containing chicken meal) and ignore signs that her problem skin may have other causes (seasonal allergies, parasites, flea allergy dermatitis).

Post-hoc fallacy, formally called post hoc, ergo propter hoc, translates to “after this, therefore because of this.” This common logical fallacy is the cause of many superstitions and false beliefs. We commit a post-hoc error whenever we assume that because two events occur together, with one following the other in time, that the first event caused the second event.

We are especially prone to these in nutrition precisely because we can easily change the food that we feed and because we tend to change foods only when our dogs experience a problem. If the dog’s condition improves after changing her food (and the timeframe encompassed by “after” may be days, weeks, or even months), then the improvement is immediately attributed to the change. However, if no positive change is observed, diet is still not eliminated as a cause. Rather the change may not have been the right diet. The owner moves on to another food, another supplement, and another dietary approach. (Because of confirmation bias the misses are also often not noticed, while the hits are celebrated.)

Illusion of control: Because as owners we actually are in complete control of what our dogs eat and when they eat it, the jump to assuming (hoping) that we can control our dogs’ health entirely by what we feed to them is pervasive. Proponents of nutritional trends that make extravagant claims exploit our deeply ingrained desire to be able to control health changes in our pets through what we choose to feed them. It is no wonder that we fall for these claims, given our strong desire to help our dogs and the natural tendency of our brains to convince us that we have a universal ability to do so.

The availability error is rooted in our natural tendency to attach greater significance to events that are easily brought to mind or remembered (i.e., are “available”). Like most cognitive biases, the availability error has its roots in a heuristic that our brains use for speed and efficiency when evaluating incoming information. It can lead to errors in judgment when we would be better served to take our time and evaluate information more objectively.

Examples of the availability error include the belief that shark attacks, child abductions, and plane crashes are far more common (and present much greater risk to individuals) than they actually are. An unfortunate but common example occurs when people believe that all Pit Bull Terriers are dangerous because of sensationalized media coverage of dog bites that focuses repeatedly only on this particular breed or breed type.

Negativity bias refers to the psychological phenomenon in which we naturally pay more attention to and give more weight to negative rather than positive experiences. It is this unconscious bias that causes people to be more hurt or discouraged by insults or poor work performance reviews than they are pleased or encouraged by compliments or shining performance reviews.

The negativity bias can affect the attention that we pay to our dog’s health and wellness. We tend to wait until we see a change in weight, the development of itchy skin, or the onset of a serious health problem before we react. In human medicine (and increasingly in veterinary medicine), efforts to train ourselves to focus on wellness and disease prevention as opposed to disease treatment are a reflection of recognizing and trying to combat negativity bias.

Jane’s Claims

These are just a few of the ways in which our mind’s tendency to think rapidly and use shortcuts to form opinions and rules of thumb to make decisions can lead us to make errors in judgment. Let’s return for a moment to Jane’s insistence that her diet and supplement would cure Bruino’s cancer.

Upon further investigation, Pam discovered that one of Jane’s dogs had died of cancer several years previously and that Jane had changed the dog’s diet several months prior to the diagnosis. This led Jane to believe that “diet causes cancer,” examples of both post hoc and availability errors. Because she spent many hours and a great deal of effort in the development of her nutritional supplement, Jane understandably was highly invested in believing in the efficacy of her approach. Therefore, these feelings could lead her to pay more attention to dogs who responded positively (or did not suffer from it) and to ignore cases in which the dog’s condition worsened (confirmation bias).

An additional post hoc fallacy was committed when she assumed that a dog’s change in status was due specifically to her remedy because the change in condition followed feeding the remedy chronologically (regardless of how long that time period was and ignoring the effects of other treatments that a dog may have been receiving).

The fact that Jane’s remedy (and her beliefs about it) had not been shown to be effective through controlled scientific study does not discount the fact that her remedy might be helpful or effective. The point is that we just don’t know. The claims that Jane made for her nutritional approach had never been tested and the risks of succumbing to a variety of potential biases make her claims at the very least unfounded, and at the most highly suspect.

Why Dog People Need Science

So, what is a dog person to do? Are our minds, while highly efficient at processing loads of information and helping us to react quickly to changing circumstances, at the same time sabotaging our attempts to weigh evidence and make well-reasoned decisions? Well . . . yes. But when it comes to our dog’s nutritional health and well being (as well as to many other important decisions in our lives), we can use science as a rational and reliable tool to help us to avoid these traps, evaluate information objectively, and choose well.

At its most basic, science refers to a systematic approach to acquiring knowledge. The system of science uses observation and experimentation to describe and explain the natural world. And – this is important – science is specifically and intentionally designed to prevent the biases and cognitive traps that come along with being human, traps that will almost always trip us up in one way or another if we simply go about willy-nilly making decisions in response only to how we feel and without any type of system or plan.

One of the best things about science is that, by definition, it is testable. Science is designed to evaluate the validity of the stuff that you think/ponder/learn to make sure that your beliefs actually reflect reality as opposed to being flawed, misleading, or an outright falsehood.

In most disciplines, including nutrition, science is put into practice through use of the scientific method. Most of us learned the steps to this method in high school, and some of us have had the opportunity to put it into practice later in college and in our careers. There are four primary steps to the scientific method:

1. The investigator notices a natural phenomenon or a problem and takes the time to observe it closely, trying to learn as much as possible about it.

2. The investigator considers one or more possible explanations or causes for the phenomenon and typically selects a favorite for testing: her hypothesis. Now the fun begins.

3. This is the essence of the scientific method. A study is designed, data are collected and analyzed, and conclusions are drawn. The results of the first study may suggest a second, and understanding grows.

4. Following study replication (preferably by unrelated groups of researchers), the hypothesis is either rejected as false (and you start all over again), accepted, or judgment is withheld pending still more study.

A key difference between the scientific method and other ways in which we learn about the world is that it is designed to protect us from inherent biases and mistakes in reasoning. In Chapter 3, we will see how the use of well-designed studies can support or refute claims that are made about a particular pet food, ingredient, nutrient, or feeding method. For now, let’s return one more time to the issue of diet and cancer in dogs.

The Scientific Method in Practice

The scientific method provides a systematic approach to testing ideas about “how things work” that protects those doing the work (and those who stand to benefit from it) from making errors in judgment. Jane promoted a feeding approach and nutritional supplement that she was convinced would slow the progression of Bruino’s cancer. Her convictions, while sincere, were based not upon scientific evidence but upon personal experience. As we have seen, personal experience can lead to flawed conclusions. Yet, as I mentioned, we did change Bruino’s diet.

The food that Pam chose for Bruino included an increase in fat and reduced levels of digestible carbohydrate (starch). Protein was moderately increased. The type of fat was also modified to include a high proportion of a class of fatty acids called the omega-3 fatty acids. These are commonly found in certain types of fish. When included in the diet in proper amounts, omega-3 fatty acids have varying degrees of anti-inflammatory benefits to different tissues in the body. The reasons for these changes have to do with changes in the way that animals with cancer are able to use energy-containing nutrients from their diet (fat, carbohydrate, and protein) and also how being affected by cancer influences body weight, body condition, and an animal’s interest in eating.

Most animals, including humans, experience certain changes in metabolism (the way in which the body digests and uses nutrients) during cancer. These changes become most pronounced during the later stages of cancer and can also be influenced by cancer treatments such as chemotherapy and radiation.

It is known that most tumor cells preferentially use carbohydrate as an energy (fuel) source and use fat and protein far less efficiently. Therefore, feeding an animal who has cancer a diet that shifts its energy balance away from carbohydrate and toward fat is designed to feed the patient while starving the tumor. Because tumors grow fastest when using carbohydrate for energy, depriving them of this form of energy may slow their growth and slow the progression of the cancer.

An additional benefit to increasing dietary fat is that fat improves a food’s energy density and appeal to dogs, which will both encourage a dog to eat and will help to maintain body weight during treatment. Increasing omega-3 fatty acids in the diet has anti-inflammatory benefits in the body and may also help to limit tumor growth. Finally, many dogs with cancer lose weight and specifically show a loss of muscle mass and strength. Increasing protein helps to conserve the body’s lean tissue and reduce this decline in body condition.

These recommendations arise from our understanding of both canine cancer and nutritional science. Still, an approach to feeding dogs with cancer that uses this nutrient matrix must be tested (scientific method, remember) if we are to accept that a diet switch could help Bruino. Is there scientific evidence?

Indeed there is. Although there are not mountains of it, there is enough to suggest that these dietary modifications may be beneficial for dogs with cancer. (Editor’s note: the published research is referenced and described in the book.) These studies provide the science that was needed to make a decision for Bruino’s wellness and quality of life during cancer treatment.

Happily, Bruino’s new diet at the very least supported his body condition and muscle mass during his treatments. Bruino experienced a high quality of life for almost a year following diagnosis. While we cannot know if the dietary intervention slowed his cancer progression as an individual case, we do know that a dietary matrix that includes increased fat and protein, reduced carbohydrate, and increased omega-3 fatty acids has the potential to do so. And, because the food that he was fed was formulated to be nutritionally complete and had been tested, we also know that we did not harm him by feeding it.

Linda P. Case, MS, is the owner of AutumnGold Consulting and Dog Training Center in Mahomet, Illinois, where she lives with her four dogs and husband Mike. She is the author of Canine and Feline Nutrition, as well as three other books and numerous publications on nutrition for dogs and cats. Her blog can be read at

Editor’s Note: Dog Food Logic examines the types of available scientific (and not so scientific) evidence about canine nutrition that you can use to make evidence-based decisions for your dogs’ health and wellness. Further chapters include information about dogs’ nutritional requirements, how a dog’s age and activity level should affect your choice for his diet; how the pet food market and the companies that make up that market are changing; pet food marketing; label claims and how to analyze them; and pet food oversight and regulation.


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