Carbohydrates are the most argued-about macronutrient in pet food and the one you are least likely to see printed on the bag. AAFCO does not require carbohydrate content in the guaranteed analysis, which means the loudest claims about carbs are made about a number the label is under no obligation to reveal. Here is what is actually established.
No Minimum, but a Real Requirement for Glucose
Neither dogs nor cats have a dietary requirement for carbohydrate, and AAFCO nutrient profiles set no minimum for it. That does not make glucose optional. The brain, red blood cells and other tissues depend on it. When carbohydrate is scarce, the liver supplies glucose through gluconeogenesis, converting amino acids from protein and glycerol from fat into fuel. Cats are particularly efficient at this and run a higher baseline rate of protein turnover than dogs. “No requirement for carbs” and “no need for glucose” are two very different statements.
How Much Is Actually in the Bowl
Because it is rarely printed, owners guess, and usually guess high. Dry food is where carbohydrate concentrates. Typical maintenance kibble sits in a broad middle band, and grain-free recipes frequently land in the same range as the grain-inclusive version they are sold against, because potato, pea, tapioca and lentil flours replace the grain. Wet food is a different picture: high moisture and higher meat inclusion commonly push carbohydrate into single digits on a dry matter basis. Switching from kibble to canned food therefore changes carbohydrate intake far more than switching brands inside the dry aisle.
Why Kibble Needs Starch
Starch is not in the recipe purely as cheap filler. Extrusion cooks a dough under pressure and forces it through a die, and starch gelatinisation is what holds a kibble together and gives it structure. Formulas built with almost no starch generally cannot be extruded into a normal dry kibble, which is why grain-free dry foods are seldom low-carbohydrate. Cooking also helps digestion: cooking and extrusion improve starch digestibility, and cats tolerate the starch levels found in commercial diets well even though they produce only a small fraction of the pancreatic amylase that dogs do.
Fiber, Sugar and the Label Problem
Carbohydrate is not one ingredient but a family, and the family members behave differently.
| Type | What it does | Where it comes from |
|---|---|---|
| Starch | Digested to glucose; main energy source in dry food | Corn, rice, wheat, barley, oats, potato |
| Sugars | Palatability and quick energy; can be listed as dietary sugars | Molasses, syrups, some fruit and vegetable ingredients |
| Fiber | Not digested by the pet’s own enzymes; supports gut health, satiety and stool quality | Beet pulp, cellulose, psyllium, whole grains |
AAFCO permits dietary starch and sugars to be declared but does not allow a “low carbohydrate” claim, and there is no scientifically agreed optimum carbohydrate level for either species. The widely repeated 30 percent for dry dog food or 15 percent for dry cat food rules are not backed by research.
What This Means at the Bowl
- Judge the food, not the carb number. A food is complete or it is not; the source of the glucose matters less than the overall balance.
- Do not assume grain-free means low-carb. Check whether starch just moved to peas, potato or tapioca.
- Use fiber deliberately. It is the one carbohydrate fraction with a clear clinical role, in weight programs and in managing stool quality.
- Ask the maker for the full nutrient profile, including carbohydrate, if you want a real number rather than an estimate.
- Feed by calories, not by volume. Carbohydrate concentration matters mostly because it changes energy density.
The bottom line. Both cats and dogs digest and metabolise carbohydrate readily, and there is no evidence that moderate carbohydrate in a complete diet harms a healthy pet. The genuine concerns are the ones owners can act on: excess calories in any form, treating a marketing phrase as a nutritional guarantee, and assuming that a low-carbohydrate or grain-free label means a better-balanced bowl. If your pet has diabetes, obesity or another condition where carbohydrate load matters clinically, that conversation belongs with your veterinarian and the specific diet they recommend, not with a number missing from the back of the bag.