What is a food? What is nutrition? Nutrition is a vital process that is carried on only in living organisms. It is a process of development, growth, repair and invigoration. In a complex organism various processes are in continuous operation and these processes contribute to and are intended for the one great end and aim of life--nutrition. It is for this reason alone that we eat and digest, that we breathe, that we secrete and excrete. For this reason alone, the heart and arteries, the veins and lymphatics, perform their varied functions. Function is the great end and aim of life and we are men, strong, vigorous and healthy or feeble, debilitated and worn out, just in the extent to which we have good nutrition.

We cannot move a muscle nor think a thought without using up and deriving the power to do so from the organs which are the seat of the action. This is also true of our involuntary motions--digestion, circulation, etc. It follows that life can be maintained only by constant recuperation and replenishment. As every movement, however slight, expends energy and substance, exhaustion would soon result except for the provisions for recuperation. Food, therefore, is any substance which can be utilized in building and replenishing the vital organism. In short, food is building material; it is the substance out of which the physiological elements are evolved and by which the vital machinery is kept in action.

The functional processes and movements which constitute and continue us as living beings can be carried out only by means of an adequate supply of those elements the physiological combinations of which constitute the several phenomena of organic life. To serve as food a substance must be of such a character as the living organism can appropriate and transform into substance like unto or identical with its own substance. To be classed as food a substance must serve the following legitimate purposes:

    Supply materials that meet the needs of growth and development of the several organic structures from germ to the mature or perfect state. Supply new materials to the ever-wasting organism, not alone to make good its wear and tear, but also to repair damages. Supply materials for the evolution of those functional changes which constitute the vital phenomena and serve for the development and continuation of our physical structure. Supply materials for reproduction, that is, the materials needed in the evolution of a new organism.

A substance is food in proportion to its adaption to these several ends. Food includes all those substances the elements of which are convertible into, and do form, the constituent materials of the tissues. This is to say, food is material that can be converted into cell substance. As an example, bone must be replenished with the materials that enter into the composition of bone, muscles with those of muscle, nerves with those of nerve, and so on with all the tissues. In the growth and development of a new being, the same rule holds good: each organ in its unfoldment from the bud must be supplied with the organic materials which enter into and constitute its structure.

To serve in any proper sense as food a substance must be capable of assimilation by the tissues; this is to say, the cells must be able to take it up from the blood stream and incorporate it into themselves and make it a normal constituent of cell substance and use it in the processes of life. Any substance that cannot be so appropriated by the cells and organized into living structure, this is to say, any substance that cannot be metabolized, is a poison. A substance, such as alcohol, which is circulated through the body as alcohol, deposited in the body and cells as alcohol and expelled through the lungs, the skin, the kidneys and other organs as alcohol and is not changed in any way is not used and cannot be classed as a food.

Although we frequently speak of "Mother Earth," it is doubtful if we fully realize how completely and continually everything we are and everything we do comes from and depends upon the earth. "Dust of the Earth" we are and upon the earth must we depend for replenishment and growth. But we cannot go directly to the soil for the elements of our nutrition. Like all the animals below us, we must depend upon the plant for our food supplies. Animals lack the power of appropriating mineral elements and forming them into food. This can be done only by the plant. All animal foods come either directly or indirectly from the vegetable kingdom, which alone possesses the ability to take the elements of air, water and soil and synthesize these into organic materials that the animal can use.

In her organic processes nature makes use of invariable forms of materials. One animal can be food for another only as it serves as a vehicle to carry the materials previously supplied by the plant. Organizing work reaches its culmination in the plant; what takes place in the animal is largely in the nature of a re-arrangement of the work previously done by the plant.

Rock breaks down into silt; primary vegetation builds this into soil; finally, the soil is rich enough for higher forms of vegetation. The first vegetation is a rather sickly affair. Animal life cannot exist on silt. Drug store minerals are not foods. Drug store iron, for example, is of no value in anemia. If there is any deficiency of any nutrient in our body, this must be supplied in the proper form or it will not be assimilated in tissue building. We cannot build bone by eating rock lime.

It is possible to analyze an apple and ascertain its chemical constituents; but all the chemists in the world cannot make an apple, nor anything that can substitute for it. There must be a vegetable arrangement of these elements, else they are wholly innutritious. Only the plant can take the raw materials of soil, water and air, and with the use of the sun, synthesize suitable substances for animal nutrition.

The incapacity of the animal organism to assimilate inorganic phosphorus compounds and turn them into cell substance stamps them as unfit for nutritive purposes. When the practice first arose of trying to supply the body with phosphorus by giving phosphates, tests were made by Sampson of England and Dujardin-Beaumitz and others of France, and it was found that the only successful way of supplying the body with phosphorus is to employ those which have already been assimilated by the plant (or by the animal from the plant), and that when efforts were made to augment the supply of phosphates by adding soluble or insoluble phosphates to the food, these were only passed through the the body without being retained therein. Similar facts are true of other inorganic elements, such as sodium chloride, the fluorides, etc.

Animal life can be supported and continued only through the appropriation and use of organic materials. Iron, sulphur, calcium, phosphorus, although indispensable to the living organism, cannot be metabolized in their free or inorganic state, but prove to be poisons if taken in these forms. They are usable only in inorganic combinations such as those prepared by the plant.