Carbohydrates are present in almost all commercially available dog foods. While we often focus on the protein and fat content of a dog food, carbohydrates have an impact on the quality of your dog's diet. Carbohydrates are responsible for many health problems, if not fed correctly. This article will focus primarily on the non-fiber carbohydrates. There is a separate article that discusses fiber in greater detail.
The function of carbohydrates in pet food
The value of carbohydrates in dog foods is often debated among nutritionists. Despite the debate, most commercial dry foods contain between 30% and 70% carbohydrates. If we examine the diets of the wild canines that most closely resemble our domestic pets, we recognize that the wild canines do eat some carbohydrates through the consumption of berries and intestinal contents of their prey. However, it would rarely constitute even 30% of their diet. This then raises the question as to why we feed our domestic pets so much carbohydrate, when it appears to be an unnatural food source.
Dogs have the ability to consume large quantities of protein and then convert that protein into energy in addition to muscle. They also have the ability to convert many carbohydrate sources into the same kind of energy. This ability to utilize both carbohydrates and proteins as an energy source explains how we are able to feed our dogs a high carbohydrate diet, particularly when we feed processed carbohydrates that are easily digested by dogs. So, essentially we are meeting the dog's protein requirement with meat, and then meeting their energy and fiber requirements with carbohydrates instead of the protein they would often use in the wild.
Using carbohydrates as an energy source has benefits for the manufacturer and consumer. Carbohydrates are less expensive and more readily available as an energy source than proteins. Carbohydrates are also essential in the formation of dry pet food. The starchy carbohydrates are used to add structure, texture, and form to kibbled food helping to create a product that is stable and easy to feed. Canned foods could be composed without the addition of carbohydrates, but dry kibble could not exist in its current form without carbohydrates.
Carbohydrates used in dog foods
Carbohydrates used in dog foods generally include the starchy portion of a plant that can be easily broken down in the digestive tract of the dog. Soluble carbohydrates are found in high concentrations in cereal grains such as rice, wheat, corn, barley, and oats. The cooked or extruded forms of carbohydrates found in most pet foods are easily and rapidly digested. It should be noted that not all forms of starch are easily digested by dogs and cats. Raw cereal grains are digested much more slowly in the intestine and there are some starchy carbohydrates, including raw potatoes and bananas that are completely resistant to digestion in pets.
Health problems related to carbohydrates
While carbohydrates are an important part of dry commercial pet foods, they can occasionally cause medical problems in dogs including obesity and maldigestion. Obesity occurs when an animal's energy needs are exceeded and the extra glucose created by the digestion of the carbohydrates is stored as fat. Realize that an excess of carbohydrates, fats, or proteins can all lead to obesity, but carbohydrates are often the most common energy source and are easily converted to glucose.
Signs of maldigestion can range from mild to severe and often include excessive gas, bloating, and diarrhea. As carbohydrates pass through the digestive tract, enzymes such as amylase, lactase, maltase, sucrase, and disaccharidase break them down into usable forms. Animals that have deficiencies in these enzymes will be unable to adequately break down these carbohydrates. The undigested carbohydrates will then ferment and create bacterial overgrowth resulting in the production of gas and excess water creating the symptoms of maldigestion. In some animals, the lack of enzymes may be due to an actual deficiency, in others, infections or inflammation in the intestinal tract may result in a breakdown of the normally available enzymes.
Lactose intolerance is a common form of maldigestion. Young animals have the enzyme lactase, which breaks down the sugar in milk called lactose. Often, as animals age, they stop producing lactase. When that animal consumes milk products, the lactose is not digested and the symptoms of maldigestion occur. We also recognize that animals have different tolerances for the amount of carbohydrates that they can digest. Whereas, many dogs can tolerate the level of carbohydrates found in most commercial dog foods, there are some dogs that will develop maldigestion when fed these foods. If these dogs are fed a lower carbohydrate diet, or if they are fed a digestive enzymatic supplement, they can usually tolerate the carbohydrates that are present.
Soluble carbohydrates provide an affordable source of calories and play an important role in the composition of most commercial pet foods. While dogs have not evolved to eat large quantities of carbohydrates, when properly prepared, they appear to be well tolerated by most animals. Some animals have an intolerance to carbohydrates and need to be supplemented with natural enzymes or fed a reduced carbohydrate diet.