For the proper support of the human system, a combination of nitrogenous and non-nitrogenous foods is essential, with water to dissolve them and oxygen to burn them. Although air is not classified as a food it is essential to effect the chemical changes needful for assimilation. "About two thousand cubic feet of air need to pass through the lungs of an adult daily in order to furnish oxygen in sufficient quantity. If there is lack in this most important food-stuff (and nothing else can take its place), starvation as truly results as if other food were withheld, for the changes required for nutrition cannot take place, and furthermore incomplete decomposition occurs, which may result in more or less poisonous products.

"Fresh air - air with its quota of oxygen - is, then, a prime requirement in nutrition." - Ellen H. Eichards.

A Perfect Food

1. "A perfect food must contain all the nutritive elements of the body: Proteins, carbohydrates, fats, minerals, and water.

2. It must contain these in their proper proportions.

3. It must contain in a moderate compass the total amount required daily.

4. The nutritive elements must be capable of easy absorption, and yet leave a certain bulk of unabsorbed matter to act as intestinal ballast. It must be obtainable at a moderate cost." - Hutchinson.

A Mixed Diet therefore is necessary, as no "one food" fulfills all the requirements of a "perfect food." A mixed diet must be taken whereby one food may be used to supplement what is lacking in another. The foods best for health are those best fitted to the needs of the individual. The cheapest food is that which furnishes the largest amount of nutriment at the least cost. The best food is that which is both healthful and cheapest.