| Carbonaceous foods: | |
| Sugars | |
| Starches | |
| Root and tuberous vegetables | |
| Green vegetables | |
| Fruits | |
| Fats | |
| Nitrogenous foods: | |
| Lean meat | |
| Eggs | |
| Gluten | |
| Carbo-nitrogenous foods: | |
| Cereals | |
| Legumes | |
| Nuts | |
| Milk | |
The above classifications are made because of the preponderance of certain elements in them, not because they do not contain other substances; e.g. vegetables are mixtures of sugars and starches; fruits are mixtures of sugars, vegetable acids, and salts; milk, legumes, cereals, and nuts contain a more equal division of sugars, fats and proteins and are therefore represented as carbo-nitrogenous; lean meats, with the exception of shell fish, contain no starch, but all meats contain fat, protein, and water, and all, except liver, contain ash.
In the table below, examples are given of foodstuffs in which the chemical elements are almost pure representatives of their classes. Cornstarch, sago, and tapioca are almost pure starch, containing very little of any other element; glucose, cane sugar, syrups, and honey are almost pure sugar; butter, lard, and olive oil are nearly all pure fat; egg albumen, gluten, and lean meat are almost pure protein.
| Foodstuffs | Inorganic | Water | Starches | Corn Starch | ||||
| Salts | Sago | |||||||
| Tapioca | ||||||||
| Organic | Carbonaceous (producing heat & energy) | Glucose | ||||||
| Sugars | Cane Sugar | |||||||
| Syrups | ||||||||
| Honey | ||||||||
| Lard | ||||||||
| Fats | Olive Oil | |||||||
| Butter | ||||||||
| Nitrogenous— (growth and repair) | Proteins | Egg Albumen | ||||||
| Gluten | ||||||||
| Lean Meat |
The proteins contain nitrogen, sulphur, and phosphates. The predominance of nitrogen has given the proteins the name nitrogenous. The carbonaceous foods contain none of these elements, but are rich in carbon, hence the name carbonaceous.
As previously stated, no food contains but one element of foodstuffs and all elements are formed into compounds of plant life from the elements in the soil, air and water by the action of the sun’s rays. The rays of heat and light seem to store something of their power in latent heat and energy within the combinations of these compounds. The end of plant life is the completion of its compounds,—it first generates the compounds, then matures them, and then dies.
All organic matter is thus formed by the action of the sun’s rays upon inorganic matter. All meats are first in the form of plant life and are converted into other compounds by the chemical processes of the animal. This chemical action of the animal converts the energy latent in the foods into more concentrated form. The animal thus performs a part of the chemical work for man.
The classification of foods, as previously stated, is based upon the principal organic foodstuffs contained. Proteins contain carbon and salts, and carbonaceous foods contain salts and nitrogen, but these are not in appreciable quantity. The preponderance of these elements determines the use of the foodstuffs in the body. It will be remembered that the chief uses are the production of heat and energy, the building of new tissue of the growing child, and the repair of the waste in the child and the adult.
Water