Why can t dogs have carbs

By Isabella Storyclaire

last updated November 18, 2024

Contributions sourced from

Dogs and Carbohydrates A Surprising Secret Revealed

By Mike Sagman

Updated: September 27, 2023

Zero.Thats how many carbohydrates are nutritionally required by a dog to sustain life.The fact that a dog food doesnt need to contain any carbs at all seems hard to believe.

But its true.

You see, according to the National Research Council and compared to the other two major nutrients protein and fat no carbs are considered essential for a healthy canine diet.¹

Dogs dont need corn.And they dont need wheat, barley rice or potatoes, either.

Yet surprisingly, carbs represent the dominant nutrient found in most dry dog foods.

Why Dog Food CompaniesLove Carbohydrates

Since the early 1950s, dog food manufacturers everywhere have fallen head-over-heels in love with carbs because theyre:

Abundant
Durable (long shelf life)
Essential to the kibble-making process
Cheaper (per calorie than protein or fat)

Please notice that not one of these reasons has anything to do with nutrition not one.

Are Carbs Safe?

Carbohydrates arent bad for dogs.In reasonable amounts, they can actually provide a practical source of energy.

However, the problem lies in their quantity.

Using a dogs ancestral diet as a model, the total amount of carbs consumed by a dogs evolutionary predecessor is dramatically less than whats become the norm for todays kibbles.

One sensible source estimates natural carbohydrate consumption for a dogs ancestors at around 14 percent of total diet.²

Yet on average, todays dry dog foods contain somewhere between 46 and 74 percent carbohydrates.³

Comparing the Numbers

Todays kibbles contain as much as four times the carbohydrate content historically found in the canine ancestral diet.

Wouldnt it make sense for a dogs food to be more like the species ancestral diet with more protein and fat and fewer carbs?

The Bottom Line

When choosing dog food, its reasonable to favor products lower in carbohydrates.

However, since most dog food manufacturers fail to disclose the percentage of carbohydrates contained in their products, the Dog Food Advisor provides an estimate of this important figure inside every review.

So, look for dog foods rich in meat-based protein and lower in carbs.You could be adding years of better health to your best friends life.

Carb Confusion Part 1: The Role of Carbohydrate in Pet Foods

It has become trendy to advertise pet foods as being low in carbohydrate (like a wolf or a wild cat would eat) and to emphasize the type of carbohydrate sources excluded or included in diets: grain-free, potato-free, with ancient grains, or with wholesome grains. Depending on the manufacturer and the diet, carbohydrate sources such as grains, potatoes, tapioca, and legumes (e.g., peas, beans, and lentils) may be portrayed as either inexpensive fillers or wholesome, nutrient-rich and desirable components of a pet food. These two different viewpoints cant both be true, can they? Lets review some of what we know about carbohydrates and separate the facts from the fiction (or maybe the wheat from the chaff?)

What are carbohydrates?

Carbohydrates are digestible sugars (for example, glucose) and starch, which is made up of long branching chains of glucose molecules. The vast majority of carbohydrates in pet foods are provided by plant-sourced ingredients. Digestible carbohydrates are separate from fiber, which while biochemically is considered a carbohydrate, cannot be digested by the digestive enzymes in pets guts, and is instead utilized to varying extents by their gut microbes.

Do dogs and cats need carbohydrate in their diet?

Dogs as omnivores and cats as carnivores have evolved differently with respect to their needs and tolerance for carbohydrate in their diets. Generally, adult non-reproducing animals of both species have no specific requirement for carbohydrate in their diet. The cats native diet is low in carbohydrate, consisting mainly of whatever is found in the gut contents of their prey. As such, even very low carbohydrate diets can be safely fed to many cats of all life stages although the nutritional properties of these types of diet may not be ideal for all cats and especially for cats with some health concerns. Growing and non-reproducing dogs also have no requirement for carbohydrate; in pregnant and lactating dogs, reproductive success has been shown to be better on diets that contain carbohydrate than on carbohydrate-free diets with similar protein concentrations. However, just because dogs and cats can survive on low carbohydrate diets, it doesnt mean its ideal for all dogs and cats.

Can dogs and cats digest and utilize carbohydrate in their diet?

Both dogs and cats have the ability to digest and metabolize properly cooked carbohydrates in amounts that are found in commercial pet foods. However, cats cannot metabolize fructose, a specific type of sugar found in fruit, table sugar, and corn syrup and it is excreted in their urine unchanged. Because of cats higher protein and fat needs relative to dogs and lower activity of the enzymes used to digest carbohydrate, foods for healthy cats are usually lower in carbohydrates than foods for healthy dogs.

Dogs typically have a high tolerance for carbohydrate and can obtain large percentages of their daily calories from carbohydrates (up to ~75% of calories), especially if medical conditions limit the amount of fat or protein that can be safely fed. In fact, one of the most dramatic genetic differences between dogs and wolves is that dogs have many more copies of the gene that codes for amylase, the pancreatic enzyme used to digest starch, showing that they evolved from wolves to be more adept at processing carbohydrate.

What are potential benefits of carbohydrates in pet food?

Pure carbohydrates provide a source of energy around 3.5 to 4 Calories per gram the same as protein. But, most carbohydrate sources traditionally used in pet foods are more complex, such as whole grains, and provide nutrients such as fiber, antioxidants, essential fatty acids (both omega-3 and omega-6), vitamins, and minerals. Every carbohydrate source is a bit different oats are high in soluble fiber and the essential fatty acid linoleic acid, while wheat and beans are higher in protein, and sweet potatoes are very good sources of potassium and beta-carotene (which is made into vitamin A in dogs and serves as an antioxidant in cats and dogs). Fiber contained in the carbohydrate sources can nourish healthy gut bacteria and improve stool quality. Therefore, grains and other carbohydrates in pet food are not there as fillers they actually provide valuable nutrients and properties to the diet!

Carbohydrate in pet food can also have indirect benefits. As all calories must come from protein, fat, or carbohydrate, having more carbohydrate in the diet can allow for lower protein or fat that can help to address a health issue or to reduce the calories (fat provides more than twice the calories of protein or carbohydrate).

Can carbohydrate be harmful to pets?

There is little evidence that even high amounts of carbohydrate in high quality, complete and balanced pet foods pose any health risks to pets. The rare pet may not tolerate a specific carbohydrate source (but food allergies are more common to animal products than to plant products!) and some individual cats with gastrointestinal abnormalities may have reduced ability to digest carbohydrates compared to the average cat. But there are few clear links between dietary carbohydrate and any health issues in dogs or cats.

While a few studies have suggested that eating dry diets (which are often higher in carbohydrates than canned foods) may be a risk factor for obesity and diabetes in cats, this is likely because dry foods are more calorie-dense than canned foods and are often fed free-choice. Unlimited amounts of high calorie, palatable foods will lead to weight gain in the majority of cats. It is that weight gain and the metabolic changes that come along with obesity that are the biggest dietary risk factors for diabetes in cats, not the amount of carbohydrate. For dogs, there is no evidence of a link between diabetes and dietary carbohydrate.

One situation where it may be advisable to reduce dietary carbohydrate would be in a pet that has already been diagnosed with diabetes. Particularly in cats, reducing dietary carbohydrate can improve diabetic control, but this strategy is not optimal for all cats and data are lacking on what amounts or types of carbohydrate are most appropriate. It is thus important that the diet be individualized for each pet with diabetes.

For pets with some gastrointestinal conditions, it may be desirable to adjust the amount or type of dietary fiber or carbohydrate (as well as the fat, digestibility and other factors) to find the optimal combination for a specific pet.

How do I compare the types and amounts of carbohydrate in a pet food?

Unfortunately, it can be difficult to compare the amount and type of carbohydrate in pet foods or predict the metabolic effect that increases or decreases of carbohydrate will have on a specific pet. Stay tuned for a future post where we discuss those issues in more detail Carb Confusion: Part 2: Measuring and Comparing Carbohydrate in Pet Foods

Featured Image by marco aureliofromPixabay

Dr. Cailin Heinze is a Board-certified Veterinary Nutritionist and the Executive Director and Chief Academic Officer of the Mark Morris Institute, a non-profit organization whose mission is to promote optimal companion animal health by providing educational opportunities for veterinary students and veterinarians in clinical nutrition. She has also done some consulting work for Balance IT, a company that makes software and supplements for home-cooked pet diets. She is an expert in home-cooked diet formulation and general pet nutrition and has a special interest in feeding pets with kidney disease and cancer.

Want to read more information on feeding your pet?

Subscribe to always know when we add new material!

Dogs and Carbs: Its Complicated

The question of how best to feed dogs stimulates great debate and evokes strong emotions among dog folks. (Yes, this an intended understatement.) One of the most contentiously defended viewpoints in recent years is that dogs should not be fed diets that contain digestible carbohydrate (starch).

Two primary arguments are used to defend this position. These are:

A) Dogs are carnivores and have no dietary requirement for carbohydrate.

B) Dogs are unable to efficiently digest starch. Therefore, including starch-providing ingredients in dog foods is unhealthy and provides no nutritional value.

Like many persistent beliefs, there is some truth and some falsehood in both of these blanket claims. Lets start with the first.

PROPOSED: Dogs are carnivores and have no dietary requirement for carbohydrates.

The first bit is false; the second bit is true. Dogs are classified within the taxonomic order of Carnivora, but like many other species within this order, dogs are omnivorous.

Tommy Maenhout | Dreamstime.com

The term omnivore simply means that an animal consumes foods that are of animal and plant origin (dogs do this) and can derive essential nutrients from both animal and plant foods (ditto). Based upon this definition, animal nutritionists consider the dog to be an omnivore. By contrast, the domestic cat, along with other felid species, is classified as an obligate carnivore. This classification means that cats cannot derive all of their essential nutrient needs from plant foods and therefore have an obligate need for foods of animal origin in their diet.

The fact that dogs are omnivorous does not signify that they are not predatory (they are), nor that they do not seek out and enjoy eating meat (they do). All that it means is that dogs can consume and derive nutrients from both animal and plant matter.

If we consider the dogs feeding behavior, it is clear that the majority of dogs enjoy and probably prefer to consume meat in their diet. However, they also scavenge and ingest a wide variety of food types, including starch-containing foods. Nutritionally, just like bears, who also preferably seek out animal source proteins, dogs are omnivores.

Personally, I am baffled as to why omnivore has become a fighting word among dog people. This label does not turn the dog into a carrot-munching, Birkenstock-wearing, canine hippie. Rather, it simply describes what the dog eats and is capable of deriving nutrients from: meat and plant matter. Thats all. Time for us all to calm down about this one.

Lets move on.

So what about carbs? Its true that dogs have no dietary requirement for carbohydrates; they can derive all the nutrients they need from protein and fat.

That said, cooked starch can provide a highly digestible energy source to dogs when included in their diet. From a nutrition standpoint, dietary carbohydrate spares protein. This means that when a body uses carbohydrate to provide needed energy, dietary protein is conserved from being used for this purpose and continues to be available for use to provide essential amino acids, build and repair body tissues, and support a healthy immune system. Therefore, including at least some digestible carbohydrate in the diet of dogs is generally considered to be beneficial.

The controversy about starch in dog foods revolves more around how much starch is in the food and the source of that starch, rather than its absolute presence or absence. Dogs can thrive on low-carbohydrate diets provided such diets are balanced and contain all of the essential nutrients. Diets formulated in this way are often highly palatable because of their high proportions of protein and fat. These foods are also generally very energy dense (lots of calories packed into a small volume of food), which means that portion control is important to ensure that dogs maintain a healthy weight.

Now for the second persistent statement that is often made about the dogs nutritional requirements:

PROPOSED: Dogs cannot digest starch.

It should be obvious from the vast majority of dogs who survive on carb-heavy kibbled diets that this is unequivocally false. Dogs efficiently digest cooked starch, just like humans. However, they cannot digest raw starch (and neither can we).

Cooking results in the expansion of the small granules that make up starch, which allows digestive enzymes better access and increases digestibility. This is true for humans as well as for dogs, and this fact explains why we generally do not munch on raw potatoes.

We actually know the exact degree to which cooking increases digestibility of various starches. Ground grains such as rice, oats, or corn are about 60 percent digestible when fed raw to dogs. Cooking these ingredients increases the dogs ability to digest them to almost 100 percent! This means that if you feed your dog 100 grams of uncooked oats or rice, only 60 grams will make it into his body to nourish him; 40 grams ends up in the large intestine where microbes ferment some of it, and a lot of that 40 grams ends up in your yard, as feces.

Conversely, when cooked, almost the entire 100 grams are digested and absorbed to nourish your dog. Again, not to put too fine a point on this, but the same holds true for humans.

The AMY2B Enzyme

Like humans, dogs have an enhanced ability to digest starch-containing ingredients, a change that has been directly tied to domestication. In 2013, a ground-breaking paper by Erik Axelsson of Uppsala University in Sweden identified a host of genetic changes that occurred as dogs evolved from their wolf ancestors.1 Three of these changes were alterations of key genes that code for enzymes involved in starch digestion, most notably and consistently, one labeled AMY2B.

This gene codes for the production of pancreatic amylase, an enzyme that functions to digest dietary starch. Although variation exists among individual dogs and breeds of differing geographic origin, the increased copies of the AMY2B gene correlate with higher levels of circulating pancreatic amylase in a dogs blood, which means that higher AMY2B leads to more efficient starch digestion.2, 3, 4

On average, dogs have a sevenfold higher copy number of this gene when compared with present-day wolves. These changes in the dogs genetic makeup coincide with the expansion of human agricultural practices and increased reliance upon starch-providing plants in both human and dog diets.

Dog Food Diet Selection

It is a fact that domestic dogs are better adapted to scavenging and to a diet that is higher in starch-containing foods than were their wolf-like ancestors. However, just because dogs can consume and digest starch, it does not necessarily follow that a diet that contains a high proportion of digestible carbohydrate is the healthiest way to feed them. One way of determining how much protein, fat, and carbohydrate dogs should have is to ask the dogs directly.

Yevheniia Sednieva | Dreamstime.com

Historically, nutritionists have viewed diet selection in animals principally from the standpoint of energy balance. The basic assumption was that all animals, including dogs, eat to meet their energy (caloric) needs first. However, in recent years this premise has been challenged.

There is evidence that a wide range of species, including many birds, fish, and mammals, will self-select diets containing consistent proportions of the three major macronutrients -protein, fat, and carbohydrate and that they regulate and balance their nutrient intake to maximize lifespan and reproductive fitness.

The recognition that macronutrient selection can be a driver for appropriate diet selection has led to several new studies with dogs and cats.

Domestic cats were studied before dogs and were found to consistently select a diet that was high in protein and fat and low in carbohydrate.5 This profile is consistent with that of other obligate carnivores and with the cats wild feline cousins. Interestingly, a recent study found that cats preferentially balanced their diets to a set protein:fat ratio, even when offered foods of different flavor preferences and containing animal- or plant-based protein sources.6 Although flavor and smell were important influences, the strongest factor for food selection appeared to be the total amount of protein in the food, rather than its source.

To date, only two controlled studies have been completed with dogs. In both, dogs have also demonstrated a similar talent to their feline friends for self-selecting the macronutrient content of their diets.7,8 The studies were conducted by different research teams and used somewhat different methodologies, but both reported that dogs preferentially selected diets that were low in carbohydrate and high in fat and protein.

When expressed as a percent of energy, dogs gravitated to a general distribution of 30 to 38 percent protein, 59 to 63 percent fat and 3 to 7 percent carbohydrate. Interestingly, wolves self-select diets that are even lower in carbohydrate: only about 1 percent. Initially, the dogs in these studies were attracted to very high fat diets, but over a period of several days reduced the proportion of fat and moderately increased protein.

An important finding of the most recent study was that when dogs were allowed to choose these dietary proportions over a period of 10 days, they substantially over-consume calories. Because of this, on average the dogs gained almost 3.5 pounds in just 10 days of feeding.

Its Complicated

At this point in time, we know that dogs can better digest starch in their diet compared with their wolf ancestors (and with present-day wolves). This increased capability is at least partially due to an increase in the production of pancreatic amylase.

We also know that, like us, dogs digest cooked starches very efficiently, but cannot utilize raw starch. The inclusion of at least some level of starch in a dogs diet provides an efficient source of energy (calories).

Finally, most recently, we have learned that when given the choice, dogs preferentially select a diet that is low in starch and high in protein and fat. However, self-selection of this type of diet (if fed without portion control) may lead to overconsumption and weight gain.

Still, none of this information provides evidence for the healthfulness of a diet containing some starch versus a diet that contains very low (or no) starch in terms of dogs vitality, ability to maintain a healthy body weight and condition, development of chronic health problems, and longevity.

This has not stopped proponents of low-carb or carb-free diets from making such claims, however. The fact that dogs gravitate to a diet that is high in protein and fat and low in starch is not to be confused with evidence that such a diet has been proven to be healthier or is capable of preventing illness. We simply do not know.

What we need is evidence of whether or not dietary carbohydrate is harmful, beneficial, or, well, neither. Dogs are generalists after all. It is quite possible that they, like many animals, are capable of thriving on a wide variety of diet types, including those with some level of starch.

Like I said, its complicated.

Cited Studies

1. Axelsson E, Ratnakumar A, Arendt ML, et al. The genomic signature of dog domestication reveals adaptation to a starch-rich diet. Nature 2013; 495:360-3642. Arendt M, Fall, T, Lindblad-Toh K, Axelsson E. Amylase activity is associated with AMY2B copy numbers in dogs: Implications for dog domestication, diet and diabetes. Animal Genetics 2014; 45:716-7223. Arendt M, Cairns KM, Ballard JWO, Savolainen P, Axelsson E. Diet adaptation in dogs reflects spread of prehistoric agriculture. Heredity 2016; 117:301-3964. Reiter T, Jagoda E, Capellini TD. Dietary variation and evolution of gene copy number among dog breeds. PLOSone 2016; 11:e011488995. Hewson-Hughes AK, Hewson-Hughes VL, Miller AT, et al. Geometric analysis of macronutrient selection in the adult domestic cat, Felis catus. Journal of Experimental Biology 2011; 214:1039-10516. Hewson-Hughes AK, Colyer A, Simpson SJ, Raubenheimer D. Balancing macronutrient intake in a mammalian carnivore: disentangling the influences of flavor and nutrition. Royal Society of Open Science 2016; 3:160081.7. Hewson-Hughes AK, Hewson-Hughes VL, Colyer A, et al. Geometric analysis of macronutrient selection in breeds of the domestic dog, Canis lupus familiaris. Behavioral Ecology 2013; 24:293-3048. Roberts MT, Bermingham EN, Cave NJ, Young W, McKenzie CM, Thomas DG. Macronutrient intake of dogs, self-selecting diets varying in composition offered ad libitum. Journal of Animal Physiology and Nutrition 2018; 102:568-575

Linda P. Case is the owner of AutumnGold Consulting & Dog Training Center in Mahomet, Illinois. Linda is the author of Dog Food Logic, has a new book, Dog Smart, and writes The Science Dog blog.