The confusion with carbs: can dogs eat carbohydrates?
Carbohydrates are a major component within the diet for both humans and dogs. However, high-protein, low-carbohydrate diets have become popular for pet owners and their dogs. This has led some pet owners to believe that carbohydrates are not necessary, or potentially harmful to feed to their dogs.
What are carbohydrates?
Carbohydrates are one of the macronutrient groups – along with protein, fat, fibre and moisture – found in food. Carbohydrates can broadly be split into two groups: simple and complex carbohydrates.
Glucose is a simple carbohydrate, as it does not need to be broken down by the body. Simple sugars provide the body with a quick and readily available source of energy.
In comparison, complex carbohydrates are made by these simple sugar molecules being bound together in a long branching chain. Complex carbohydrates include starch and fibre.
Starch is a common complex carbohydrate that gets digested in the small intestine. Upon digestion, the bonds holding these sugar molecules together are broken up by enzymes. The body will then use these sugar molecules as a source of energy. Starch can be found in high quantities in ingredients such as rice, oats, wheat, and potatoes.
Fibre is also a complex carbohydrate. However, the bonds holding the sugar molecules together are in a different orientation that the enzymes of the mammalian small intestine cannot break up. For this reason, fibre is considered indigestible. That being said, fibre is still particularly important to have in the diet, as the microbes found in the large intestine can use fibre as an energy source. This will help support the growth of a population of healthy bacteria within the gut.
Can dogs digest carbohydrates?
Dogs have the ability to digest and utilize starch. In fact, adaptation to a starch-rich diet is believed to have been a crucial step towards the domestication of dogs.
Similar to humans, carbohydrate digestion starts with the mouth when food is chewed. Dogs have very limited amounts of the enzyme (α-amylase). Enzymatic digestion of starch instead starts in the small intestine, where α-amylase is released by the pancreas. The amount of α-amylase secreted by the pancreas increases with increasing amounts of starch.
The α-amylase breaks the bonds holding the glucose units within starch together. Glucose will then be transported and absorbed through the small intestine, to end up in circulation. Once in circulation, glucose can be used in many ways, depending on the energy needs of the body.
Glucose can be used for energy (ATP) production. Alternatively, excess glucose can be stored in in the liver or muscles for later use (ie: glycogen). This stored glucose allows the body to maintain stable blood glucose levels when concentrations are low (ie: when food is withheld). Excess glucose can also be converted to fat and stored within adipose issue, physiologically a long-term energy depot.
Overall, diets containing 35 – 40% starch on a dry matter basis (when moisture in diet is removed) have been found to be over 99% digestible by dogs.
Does my dog need carbohydrates?
Dogs do not have a requirement for carbohydrates, meaning it is not considered to be an essential nutrient, except when they are pregnant or lactating. Carbohydrate-free diets fed during pregnancy and lactation can result in an increased mortality rate of the puppies as well as hypoglycemia for the mom. However, although the body can produce glucose, it is the only energy source that the brain and red blood cells can use, so a steady supply is important.
If carbohydrates are not provided in sufficient amounts to meet the energy requirements of the dog, the body will start to rely on protein to provide the dog with glucose for energy. Protein is a less efficient energy source than carbohydrates and is needed for other essential functions within the body, such as growth, tissue repair and immunity.
Additionally, fibre is needed in the diet to help maintain a healthy digestive system and normalizing bowel movements and fecal consistency. Fibre is also especially useful in the diets of dogs that need to lose weight or that are prone to gain weight. Since it cannot be digested in the small intestine, it adds little energy to the diet. As a result, it can help to reduce the energy density of a pet food. Fibre also plays a role in increasing satiety, the feeling of fullness, and managing blood glucose and cholesterol.
Additionally, carbohydrates are needed to provide structure to dry pet food. Although canned, fresh and wet diets will typically contain a smaller percentage of carbohydrates than a kibble would, carbohydrates are also required in wet food to achieve a desired texture.
It is also important to remember that the ingredients used as carbohydrate sources in pet foods often contain other important nutrients, such as essential fatty acids, antioxidants, vitamins, and minerals.
Are carbohydrates bad for my dog?
There is little evidence to support the belief that feeding carbohydrates to dogs has any negative health effects. There is no published evidence of an association between carbohydrate intake and the development of diabetes, obesity, adverse food reactions or any other health condition in dogs.
In regard to weight gain and obesity, the amount of energy consumed by the dog is important. Dogs will gain weight when they consume more calories than they need, regardless of whether the calories come from fat, protein or carbohydrates. Carbohydrates provide the same amount of energy per gram as protein, and less than fat. Therefore, increasing the amount of carbohydrate in the diet can allow for a decreased quantity of fat, which will be beneficial for weight loss and weight maintenance.
Additionally, a diet with a high inclusion of fibre can be especially beneficial for weight management as it may make the dog feel more full and will have a lower energy density per gram. This will help limit the amount of food that they consume and may result in a reduction in body fat and weight.
As dogs develop a type of diabetes that more closely resembles type 1 diabetes in humans, carbohydrate intake is not believed to be risk factor for the development of canine diabetes. The autoimmune destruction of pancreatic beta cells that occurs with canine diabetes is believed to be multifactorial and appears to be influenced by various environmental and genetic factors instead. There is no published research linking carbohydrate intake to the development of diabetes in dogs. Of course, treatment of diabetes is different. Simple sugars should be avoided for diabetic dogs. Although not common, simple sugars may be found in some commercial canned or semi-moist diets, especially those that contain sauces. These simple sugars may be listed as glucose, sucrose, sugar and/or caramel syrup.
In contrast to simple sugars, starch must be broken down and digested before it is absorbed. Therefore, blood glucose and insulin responses after the consumption of starches will be lower than after the consumption of simple sugars. Similarly, there has been research investigating the benefits of dietary fibre in the management of canine diabetes mellitus. The viscosity of dietary fibre lowers blood glucose concentrations following a meal and results in smaller fluctuations in blood glucose concentrations.
Carbohydrates are not typically a concern for food allergies. However, any dietary protein has the potential to be allergenic and cause an immune reaction. Protein can be found in carbohydrate-rich ingredients, including ingredients commonly used in pet foods, such as wheat and soy. However, wheat and soy are not among the most commonly reported food allergens for dogs. Gluten intolerance in dogs is extremely rare and has only been well-described in Irish Setters and more recently in Border Terriers. Similarly, gluten intolerance is linked to the protein fraction of grains such as wheat, barley and rye, rather than to the carbohydrate fraction. To diagnose and treat food allergies, your veterinarian may change your dog’s diet to include both a novel protein and a novel carbohydrate source. Be sure to speak to your veterinarian if you suspect a food allergy.
Overall, carbohydrates are important in the canine diet as they provide a source of energy and can help support digestive function and overall health. Published research has found dogs to be very capable of metabolizing substantial quantities of carbohydrates, without concern. Despite the concern that some dog owners may have over feeding carbohydrates, there is no evidence to confirm any negative health effects of carbohydrates in the diet of dogs.
Written by:
Dr. Alex Rankovic, MSc, PhD
Reviewed by:
Shoshana Verton-Shaw RVT VTS-Nutrition
Dr. Adronie Verbrugghe DVM, PhD, Dip ECVCN
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