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. _Cane sugar_ (sucrose) is derived from the juice of the sugar cane and from beets. One-third of the world’s supply of sugar is derived from the sugar cane and two-thirds from beets. From two to ten per cent. of sucrose may be obtained from the maple tree. It is also found in the sugar pea. All sugars are carbohydrates—carbon, hydrogen, and oxygen—the oxygen and hydrogen being in the proportions which form water (two atoms of hydrogen and one of oxygen). _Brown sugar_ is granulated sugar in an early stage of refinement. _Maple sugar_ is obtained by boiling down the sap of the maple tree. It is often adulterated with other sugars or with glucose from corn, because they are cheaper. This adulteration does not make it unwholesome, but causes it to lose its distinct maple taste. The nutritive value of sugar is said to be about ninety-five per cent. _Glucose_ was formerly derived almost entirely from grapes. Later the process was discovered by which the starch in corn was converted into glucose. It is produced so much more cheaply from corn that this is now the chief source of supply. Glucose is also found in most of the fruits, in combination with other sugars. It needs little change to be absorbed by the system and quickly overloads the digestive apparatus if much of it is eaten. It is pure, wholesome, and cheap, and for this reason it is often combined with other sugars. It is not so sweet as cane sugar, though just as nutritious. Many of the syrups on the market are made from it. Candy is often made from glucose instead of from molasses or cane sugar. Much candy, unless one is actively exercising, tends to produce indigestion. While glucose is wholesome, it ferments readily. Before sugar can be used by the system, it is changed into the easily absorbed form of the sugar in grapes, by a ferment in the small intestine. Hence digested sugar in the body is called grape sugar.