Carbohydrates are the chief components of diet (50–60% of energy per day must come from them). They include polysaccharides (starch, glycogen, cellulose, etc.), disaccharides (sucrose, lactose, maltose, etc.) and monosaccharides (glucose, fructose, galactose, etc.). After digestion, monosaccharides are absorbed from the intestine into circulation and transported to all the cells of body. Glucose is the main carbohydrate involved in cellular energy production. It is central to all of metabolism. It is the universal fuel and source of carbon for synthesis of most of the other compounds (both carbohydrate and noncarbohydrate). Other monosaccharides can be converted into glucose and have the same fate.