Carbohydrates have a variety of functions in the animal organism; the most important is to supply energy for the body functions. Even though fat yields more energy per unit body weight than carbohydrate (9 calories per gram, as compared to 4 calories per gram), the intake of carbohydrate is greater than fat in the normal diet.
The functions of carbohydrates are discussed below:
1. As a source of energy:
The main function of carbohydrate is to supply energy for the body processes. A greater part of the energy in the diet (more than 50-80%) is supplied by carbohydrates. Some of the carbohydrates are immediately utilized by the tissues and the remaining is stored as glycogen in the liver and muscles and some are stored as adipose tissues for future energy needs.
2. Protein-sparing action:
Carbohydrates are mainly utilized by the body of fulfilling the major part of the energy needs, thus sparing protein for tissue building and repairing. The first physiological demand of the body is the need for energy, which must be satisfied before the nutrients are used for other functions. So, this function of carbohydrates to spare protein for its primary purpose of body building and repair of tissues is an important one.
3. Essential for Fat Oxidation:
Even though fat yields twice as much as energy as carbohydrate for unit weight, carbohydrate is essential for oxidation of fats. The common expression that 'fat burns in the fire of carbohydrates' is used to emphasize that in absence of carbohydrates, fats cannot be oxidised by the body to yield energy. Recent studies have shown that oxalacetic acid, a breakdown product of carbohydrate is essential for the oxidation of acetate, which is the breakdown product of fats. In the absence of oxaloacetic acid acetate is converted into ketone bodies, which gets accumulated in the body and the person suffers from 'Ketosis'- a toxic condition of the body. Ketosis occurs in diabetes, where the cells cannot utilise carbohydrates and in starvation, where the cells must use fat stores in the body as a source of energy.
4. Role in gastro-intestinal function:
Carbohydrates play an important role in the gastro-intestinal functions of mammals. Lactose promotes the growth of certain desirable bacteria in the small intestine which brings about the synthesis of certain B-complex Vitamins. Lactose also enhances the absorption of calcium. Cellulose provides fiber and bulk which helps in the stimulation of the peristaltic movements of the gastroinl tract.
5. Add flavor to the diet:
Carbohydrate foods add flavor, variety and the diet. Since they are non-irritant, easily digestible when cooked are consumed i amount and forms the staple food of human beings.