Carbohydrates is a term that covers molecules composed of carbon, oxygen and hydrogen that have certain chemical characteristics in common. Carbohydrates are predominantly vegetable, with the exception of blood glucose, glycogen in the muscles and the liver, and milk lactose. All vegetables contain carbohydrates, ranging from saccharose in beet to the most indigestible fibre in tree bark.
Cats an dogs can live without carbohydrates in their food, as they synthesise the carbohydrates they need for the cells from amino acids. The intake of carbohydrates does however greatly improve the body's functioning.
While glucose, saccharose, lactose and starch have the sole function of furnishing energy, their botanical origin and how well they are cooked influence their digestion. The presence in the food of poorly cooked starch can cause diarrhea. Fiber, which is also a carbohydrate, is very good for transit and for the balance of bacterial flora. This is true of fructo-oligosaccharides (FOS) and mannan-oligosaccharides (MOS) for instance.