There is no nutritional requirement for carbohydrates for dogs. There is also none for fiber, though we well recognize the benefits, and the same could be said for other nutrients like glutamine, Vitamin C and even probiotics. Carbohydrates (in the form of starches) contain calories. Grains contain carbohydrates, vitamins, minerals, fatty acids, fiber, and a little protein.
Recently, carbohydrates (presumably starch, in particular) included in diets for dogs have been vilified, especially in the form of grains such as rice, wheat, corn, barley, oats, etc. The reasons are myriad:
Fallacy 1: Dogs have a shorter GI tract than people, so they cannot digest grains unless they are partially digested first.
Fact: Decades of research proves that dogs digest grains as well as starch quite well.
• The lack of salivary amylase has been stated to be one reason why dogs don’t digest carbohydrates well. Why would dogs need salivary amylase when they gulp their food? Dogs produce potent pancreatic amylase as well as ‘brush border’ enzymes to digest their carbs (like humans).
• Most digestion of carbohydrate occurs in the first part of the small intestine (like humans).
• Some have stated that dogs have more acidic stomachs and retain food in their stomachs longer than people, making a meat based diet more suitable for dogs since protein is initially digested in the stomach. The pH of the dog's stomach ranges from 1.08 to 5.5 (Ouyang et al., 2006, Smith, 1965, Buddington et al., 2003, Sagawa 2009). For people, the pH ranges from 1-4 (Krause's Food and Nutrition Therapy). This makes the acidity equivalent between the species, with the dog ranging slightly more alkaline in certain settings.
It is true that like humans, dogs cannot digest cellulose, a single structural carbohydrate used by plants to form stalks, seed coats, vegetable structure etc. Only herbivores like cows can digest cellulose, turning it into some other vital nutrient, but it doesn’t seem reasonable to compare the GI tracts of dogs and people to cows. Canine digestive physiology resembles human digestive physiology much more closely, so grains and veggies should be cooked or ground as finely as possible (either before or during the act of chewing) to derive the benefits contained in them.
Fallacy 2: Feeding carbohydrates place stress on the pancreas.
Fact: The pancreas was created to produce enzymes to digest fats, proteins and starches. That’s its job. Many people feed digestive enzymes as a daily supplement, I suppose to support what they see as this delicate flower of an organ do its job with protein and fat. There is evidence that supplementing enzymes actually downregulates the pancreas’ own production of proteases. That’s not necessarily a good thing – see my blog from 1-27-09 for more information. But during bouts of pancreatic inflammation (otherwise known as pancreatitis), where those very enzymes are released to cause inflammation and damage to the pancreas and surrounding organs and tissues, the treatment is to reduce fat in the diet in order to suppress production of those enzymes. The treatment is…….high starch diets - and they work.
Fallacy 3: Since food moves through the GI tract rapidly, there is no time to ferment carbohydrates and therefore no need for them. Because carbohydrates are not fermented, if they are included in the diet they will cause gas and voluminous stools.
Fact: Like humans, dogs harbour many lactic acid producing bacteria which ferment starch and soluble fibers contained in grains. This fermentation itself can cause gas. Odiferous gas can also be caused by clostridial organisms. Clostridia are more numerous in the GI tract when dogs are fed a high meat, high fat diet such as raw, grainless diets.
Fallacy 4: Grains cause allergies.
Fact: If dogs have the genetic predisposition to develop food allergies, they can become allergic to certain foods. A recent review of 7 studies indicates that dogs are most commonly allergic to the proteins in the following foods (in descending order): beef, dairy, wheat, egg, chicken, lamb/mutton, soy, pork, rabbit and fish. In cats, the most common allergens are beef, dairy, fish, lamb, poultry and barley/wheat (in equal numbers), egg and rabbit in equal numbers. I will admit that I’ve seen higher numbers of corn allergy than would be suggested by these numbers, as well, but please note that grains do not constitute the majority of allergy offenders.
While dogs do not require the starch found in grains or potatoes or any other food, there are some instances where you still might derive benefit from them being there. For instance, grains (and starch-containing tubers) contain certain fibers that are beneficial for the growth of probiotic bacteria in the gut. They also contain various required vitamins and minerals. And since grains, as compared to meats, contain lower fat contents, they can be used as a “place-holder” in a diet that fills a dog up while reducing the fat content. I’ve seen people feed pitifully small amounts of raw diets to dogs whose weights needed better control. Poor hungry dogs!
This is not to say I approve of diets formulated with high concentrations of starch-containing ingredients simply to limit cost. I just want to note that there is no reason to expressly avoid them unless your dog has a specific intolerance to them or some condition that requires use of a diet that is low in carbohydrates. And remember that cats are another matter entirely- they are true, pure carnivores, and as such, should probably not be fed diets that contain noticeable carbohydrate levels.
Back to carbohydrates vs grains – take this to the bank: If it’s a dry kibble, it contains carbohydrates. This is because kibble is made by the process of extrusion, which doesn’t work without a certain minimal level of starch. So those grainless diets that sound so good, and so paleolithic – yeah, those contain carbohydrates. Just in the form of potato, tapioca, or other starch containing food.
My point is that if we are going to eschew grains, let’s do it for the right reasons, and if we instead want to avoid starch, we *have* to read the labels carefully.