Carbohydrates
The carbohydrates embrace the sugars and starches and include such substance as the starches of vegetables and grains (notably corn, rice, wheat, and the root vegetables), and the sugar of milk, of fruits, vegetables, and the sap of trees. Their chief office is to create energy.
The starches are converted into sugar, so they are together given the one name of carbohydrate. The name means that carbon and hydrogen are contained in them in such a proportion that when oxygen unites with the hydrogen, water is produced and the carbon is liberated. In this chemical process heat is produced. One gram of carbohydrate produces 4.1 calories of heat.
They are almost entirely absent from meat and eggs, the animal having converted them into fats.
When the digestive organs are in a normal condition carbohydrates are easily digested.[2] They do not play a large part in the growth of the body tissues, but they are utilized by the body to spare the consumption of the fat which is stored in the tissues as a reserve. This explains their action in preserving but not producing fat. When there is an excess of fat and the desire is to reduce, the carbohydrates should be limited that the body may call on the reserve fat for heat and energy.
Few realize that after the starches and fats have been consumed in heat and energy the tissues are consumed.
The assimilation of the carbohydrates is almost complete, so that the energy derived from them may be closely calculated.
SUGAR
There are many varieties of sugar. Those commonly used as foods are, cane sugar (sucrose), fruit sugar (levulose), sugar of milk (lactose), sugar of malt (maltose), sugar of grapes or corn (glucose), maple sugar, honey, and saccharin—a coal-tar product. They are derived from plants, from trees, and from tubers or other vegetables.