Strictly speaking, any food substance not protein, even water and mineral water, is non-nitrogenous; but in the restricted sense of food as a source of energy, it is applied to two classes of organic compounds which contain no nitrogen, viz., carbohydrates and fats.

Carbohydrates

Definition

Carbohydrates are food substances which contain carbon, hydrogen and oxygen. The oxygen and hydrogen are usually present in proportion to form the water molecule (H20). These substances have therefore been termed carbohydrates. A carbohydrate may be defined as a simple sugar, or a substance which yields simple sugar after hydrolysis.

Source

Carbohydrates come from the vegetable kingdom almost entirely. There are a few exceptions, such as glycogen and milk sugar. They abound throughout the plant world, but especially in grains, roots, tubers, or wherever the plant stores its reserves.

Function

Carbohydrates are burned up in the body to produce energy in the form of work or heat. All that is taken in excess of immediate need is stored, first as glycogen or "animal starch" in the liver and muscles; and when the capacity to store glycogen is exhausted, in the form of fat. The fuel value of fat is two and one-fourth times that of sugars and starches, so that this is a very convenient form of storage of surplus carbohydrate.

The Most Important Energy Producing Foods are cereals, potatoes, tapioca, sago, fats, sugar and honey.

Classification

Carbohydrates include the monosaccharides, as typified in grape sugar; the disaccharides, as typified in cane sugar, and polysaccharides, including starch, dextrin, gums, cellulose and glycogen: