Let food be thy medicine and medicine be thy food. ~Hippocrates

Evelyn Kass-Williamson DVM

This is a question that I still struggle with. Recently I was looking for a new food for my picky little terrier who is allergic to chicken and sometimes sensitive to other foods as well. I found a food with a good nutrient profile. The website described the clean and sustainable sourcing of the ingredients and the care taken in its preparation. So I tried some. The food smelled great, to me. Unfortunately, my dog did not agree. I introduced it slowly. She ate it reluctantly for a couple of days, then developed stomach upset. I still think this is a good food, but not for her! Each pet, like each person, is an individual with individual nutritional needs and individual preferences.

So, the truth is that there is no single right answer to this question. A food that is good for one pet may be very detrimental to another. With so many options to choose from, the best pet owner can be, and usually is, overwhelmed. And there are so many forms of food; dry, canned, fresh, frozen, freeze-dried, raw and homemade diets. How do we choose?

Since I cannot tell you the best food for your particular pet, I will give you some information to help you navigate your choices. The information I will present is primarily related to dogs. The fact is that cats are obligate carnivores, which means they need to eat primarily meat with a few additional ingredients. This will be the subject of a different article. But, what I will say is that there is compelling evidence to suggest that dry food is not appropriate for cats. A plant based carbohydrate source is required to make kibble. Plain meat when dried will simply not hold together well. Increasing carbohydrates decreases protein digestibility (1,2) which is important since cats need a lot more protein. The excess carbohydrates cause other problems as well. For now, just transitioning your cat to canned food will help a lot. You can find suggestions on how to do this and more information on the subject here.

Now, back to dogs. Let’s start with the macronutrients; protein, fat and carbohydrate. How much do dogs need? Unfortunately this is not clear. The NRC, National Research Council is an internationally recognized authority on nutritional requirements for pets. It recommends basic nutrient levels for pet foods. AAFCO, the American Association of Food Control Officers then sets specific maximum and minimum required levels based on the NRC recommendations. The theory then is that if a pet food label says that it meets AAFCO standards, it should be complete and balanced. While this is a good start, there are some flaws to this system. First, the analyzed amounts of nutrients such as protein and fat are not always available and absorbable at the time of feeding. For example, a diet containing old leather boots soaked in motor oil might have appropriate levels of protein and fat, but they would certainly not be nutritious for your pet. In addition, there is a significant variation in the recommended macronutrients between AAFCO recommendations and what some consider to be the canine ancestral diet.(3) Finally, the list of nutrients and the quantity that AAFCO recommends is not complete. This is clear in the current AAFCO proposed revisions.(4) Due to lack of knowledge of specific nutrient needs or of potential toxic effects at high levels, AAFCO recommendations may exclude certain nutrients, such as essential fatty acids or not list maximum safe levels. As the report says;

“The absence of a maximum concentration should not be interpreted to mean that nutrients without a specific maximum content are safe at any concentration. Rather, it reflects the lack of information in dogs and cats on toxic concentrations of that nutrient.”

Based on AAFCO recommendations, puppy food should provide a minimum of 23.5% of calories in the form of protein. In his book, Unlocking the Canine Ancestral Diet, the author, Steve Brown, researched the natural diets of wolves, coyotes and foxes.(2) Based on his findings, he concluded that the natural diet for dogs would contain 85-90% flesh and organ meats and 10-15% plant based material including grasses, berries, nuts and other vegetation. This equates to a diet in which 49% of the calories come from protein. That is more than double the recommended amounts listed by AAFCO for growing puppies. A typical dry food might contain 25-35% protein calories, canned food, about 30% protein calories and typical raw diets about 36% protein calories.

AAFCO does not list any requirements for carbohydrates simply because it is suspected that dogs have no need for carbohydrates, yet most dry foods contain around 45% of their calorie content from carbohydrate. Canned foods contain between 15-30% carbohydrates on a caloric basis. The ancestral diet likely contained on average about 6% carbohydrate.

Fats get a little trickier. Fats come in different varieties. There are saturated fats, monounsaturated fats and polyunsaturated fats. Each has its nutritional purpose. But the label only lists crude fat which is a combination of all fats. In fact, in spite of the fact that the NRC listed a nutritional requirement in dogs for 5 different essential fatty acids (EFAs), AAFCO only requires 1, linoleic acid. Part of the issue here is that some of these essential fatty acids are very fragile and become oxidized, or rancid, when heated and/or stored, making them potentially toxic. So, AAFCO can include them in the requirements and risk toxicity, or not require them and risk deficiency. They have opted for deficiency at this time.

Average Nutrient Content of Various Dog Food Types

Calories from Protein Calories from Fat Calories from Carbohydrate
AAFCO 23.5% 17% Not listed
Ancestral 49% 44% 6%
Dry 25% 30% 45%
Canned 27% 50% 23%
Raw 30% 60% 10%

The ancestral dog appeared to get, on average, 44% of his calories from fat. AAFCO recommends a minimum crude fat content to provide 17% of the calories. An average dry food might contain 32%, canned food closer to 50% and a typical raw diet up to 60% of calories from fat.

So based on the ancestral diet, dry foods typically contain way too much carbohydrate and not enough protein, canned and raw foods often contain too much fat. A mixture of these forms of diets may get us closer to the dietary needs of these macronutrients.

What about the micronutrients, like vitamins and minerals? Minimum levels will generally prevent deficiency disease, but may not provide optimal health. Maximum, or potential toxic levels, are simply not known for many nutrients. It seems that we were all taught that pets don’t need variety. “Just feed the same thing every day for their whole life and they will be fine.” Perhaps that was the mantra from pet food companies worried that you might switch brands. But this doesn’t make sense from a nutritional or natural history standpoint. In human nutrition, it is always recommended to get a wide variety of foods in your diet so that you have a better chance of getting all of the nutrients you need in a more balanced way. And we have learned the hard way that processed foods do not contain the same nutritional value as fresh whole foods do. Heat and pressure required to process these foods damages many nutrients making them unavailable or less available.

We know that dogs in the wild would have to change their diets based on availability of foods at different times of the year. So it makes sense to give your dog a variety of foods in different forms and to include at least some fresh whole food. I think many of us intuitively know this, which is why we like to give our pets treats. Unfortunately many treats available on the market, like many of our own snacks, contain empty calories that only encourage weight gain. When treating your pet, remember that they are carnivores who, in the wild, would eat lean meats (not that fatty prime rib) and would also nibble on plants and fruits, not potatoes and grains.

There is so much more to choosing a diet than just the nutrient content listed on the package. The quality and type of ingredients, specific nutritional needs based on health status, breed and age, how a food is stored, how long a bag of dry food lasts, how the food is fed, i.e. meal fed or free fed, if there is stress at feeding time and many more factors can affect the digestibility and nutritional value of any food. I will touch on a few of these aspects in future articles. So, for now, my suggestion to provide the best nutrition to your dog is to feed variety, as long as your dog does not have food sensitivities. You might consider a mixture of good quality dry and canned or freeze-dried raw food along with some fresh whole food snacks like lean meat, fish and fresh fruits and vegetables. If your pet has specific health issues it is best to consult a holistic veterinarian for additional suggestions. To discuss your pet’s specific needs, please schedule an appointment, so we can narrow down your choices and help your pet reach his or her optimal health.