Attempts are often made to determine the value of an article of food by using as an index to its fitness, the amount of some element contained in it; let us say phosphorus. This effort is based on a misconception of the office of these elements in nutrition. To over-emphasize the importance of any of the salts--iron, calcium, potassium--or of any of the vitamins or complettins, or of protein or carbohydrate is to overlook the essential fact that these things function in nutrition only in union with the other elements.

This law of the minimum applies even to water. It has been shown repeatedly that if water is limited to a certain extent in the diet of infants, and all the other growth essentials are adequate, growth will not take place. Children placed on dehydrated diets can be taught within a very short time to take and be content with a small amount of water. The body establishes a water balance on a very low level but does not grow.

Many scientists have concentrated on single issues, seeking in these the secrets of life. But this concentration on one detail caused them to overlook the importance of the tout ensemble. Schaumann, for example, attempted to show that beriberi (polyneuritis) is due to the loss of a phosphorus compound in the milling of whole grains. Chamberlain checked up on his assumption and found it to be wrong. Several elements are lost in the milling of grains and the troubles resulting from consuming denatured grains grow out of the total deficiency.

The effort to supply us with isolated vitamins and minerals is essentially a medical rather than a tropholgic procedure and harks back to the antiquated notions that there are "specific diseases," having specific causes and requiring specific remedies.

Every tissue builder is dependent upon all the others. The decisive factor in development is not so much the absolute quantity of the various food elements in the diet, but their relative proportions. The organism's need for one element of food may be supplied only when all other elements are supplied in relative proportions. The diet must contain a sufficiency of all essential food elements, but there must be no great excess of any of these.

The amount of any given element available for utilization by the body depends, not alone upon the proportions of other elements present in the diet, but also upon other factors. The organic salts enter into important reciprocal relationships, especially in the work of secretion, but also in the process of synthesizing new organic compounds, so that we are concerned with both a qualitative and a quantitative minimum. If an element is being fed in quantities that are adequate per se, but some other and antagonistic substance is also being given, the quantity of the first is thereby rendered inadequate. An adequate amount of calcium, for example, would be rendered inadequate by the medical administration of acids, or by acid fermentation in the digestive tract. The calcium would be exhausted in neutralizing the acids and little or none would be left for the body. An abundance of calcium coupled with a lack of sodium means trouble, for the sodium is essential to keep the calcium in solution.

The availability of a food element depends, not alone upon the amount and form of this element present in the food, but also upon the quantities of other elements present. The quantity of available calcium, for example, does not depend wholly upon the absolute quantity of calcium in the diet, but upon the quantity of mineral bases generally present in one's food. A shortage of these bases involves a drain on the calcium for purposes of acid-neutralization, and consumes an amount of calcium which would otherwise be available for assimilation.

After the alkaline salts have been consumed in neutralizing the acids in the foods themselves, the residue of these are available for storage in the body as a reinforcement of its alkaline reserve. The availability of the alkaline elements is proportioned to their excess over the food acids. This is the reason that our diet should at all times be preponderantly alkaline. McCarrison showed that an excess of fat or of unsaturated oleic acid in the food may cause a relative deficiency of iodine and enlargement of the thyroid.

MacCollum, of Johns Hopkins, states in his Pathology that there seems to be some relation between the deposition of calcium and the available supply of iron. Iron is not assimilated in the absence of copper.

An excellent example of this matter, on the positive side, is the increased protein-calcium-phosphorus retention produced by the use of orange juice. The regular use of orange juice results in an increased retention of these elements out of all proportion to the amounts of these actually present in the juice itself.

It has been found that a diet with an acid-ash residue results in a greater excretion of minerals than one with an alkaline ash. Oranges give an alkaline ash. Indeed, the addition of oranges to a decidedly acid-ash diet of much cereal, meat, and few vegetables, gives such a marked alkaline result that it shifts the reaction of the urine from a decidedly acid reaction to a decidedly alkaline one. This means increased mineral retention and also increased nitrogen assimilation.

Drs. Miller and Newell, of Iowa State College, added an ounce and a half of orange juice daily for three months to the otherwise unchanged diet of fourteen underweight children and tabulated the results. The weight of these children increased 146 per cent of the expected gain, in contrast with only 46 per cent observed during the preceding three months.

Dr. Cheney, of California, fed a group of undernourished children an orange a day. To another group he gave no oranges. During two different periods of two months each, the children who received the oranges gained an average of 141 and 118 per cent above the expected increases. The other group, without oranges, gained only 28 and 18 per cent above the expected gain. During the non-orange juice periods, including the preliminary days, the children gained an average of .08 pounds a day; with the oranges they gained an average of .3 pounds a day--approximately four times as much as without the fruit.

Failure of growth may rightly be considered a deficiency disease although, on certain types of diets, both animals and man maintain good health and proportionate development, failing only to attain their normal sizes. Except for size they seem to be normal animals. This is explained by the law of the minimum given at the beginning of this chapter. Such diets contain all the needed food elements and growth is determined by the elements least bountifully supplied.

Unfortunate experiences such as famine, war, poverty, and the ignorance that causes many people to feed upon denatured diets, prove that the laws of nutrition and growth are the same in man as in the lower animals and plants. The wise will understand.

To secure the highest possible development from food, it must be adequate in every respect. All of the food nutrients must be present in sufficient quantities and in due proportions and in digestible and assimilable, that is, available, form. This adaptation in the food is relatively more important while the child is growing most rapidly, and less important as the birth period, is receded from. Suitable variety and proper blending of foods, therefore, cannot be ignored, if we desire the highest vigor and greatest development in our children. Happily, except in isolated places and among the most poverty-stricken classes, the diet of the child may be easily controlled. Knowledge of correct feeding is needed by mothers.

McCarrison noted that under about the same conditions of filth and squalor, the Sihks and Pathans were much larger than the Madrassis and other peoples of India. He found the Sihks and Pathans eating leafy vegetables, curds and cheese, and these are lacking in the general Indian diet.

He fed a group of rats on the Sihk and Pathan diet and another group on the general Indian diet. The first group grew to great size; the second group remained small. He fed other groups on the customary Japanese diet, Philipino diet, Javanese diet and the characteristic diet of the ill-nourished English working man. The results of these diets he checked with the results of the Sihk-Pathan diet. The results were the same. All groups, except those fed on the English diet, were small in size; while the latter group attained nearly the size of the group fed on the Sihk diet but had rough coats and a combative disposition.

Experiments with Japanese school children, covering several years, show that similar additions to the regular diet of Japanese children cause them to grow to be several inches taller and several pounds heavier than the average Japanese child.

A few years ago the New York Times carried the picture of three boys of the same age (eight years); one an average American boy, of average size for his age; the other two, European boys, whose growth had been stunted by inadequate food. Neither of the European boys reached to the horizontally outstreched arms of the American boy. The European boys were victims of the war that had deprived them of food. In accordance with the law of the minimum, the growth of these two boys was relative to the element least abundant in their diet.

McCollum has repeatedly demonstrated that if a litter of rats is divided into two groups of four each, and one group is fed distilled water and whole wheat only, and the other group exactly the same quantities of distilled water and whole wheat, plus the addition of turnip or beet leaves, each rat in the first group will only attain the size of a large mouse; whereas, those in the second group will attain nearly double the size of those in the first group. Except as to size both groups of rats are "normal" in all respects.

We cannot better sum up what has gone before than in the following words of McCarrison: "It is unwise to consider any of the essential ingredients of food, whether proteins, carbohydrates, fats, salts, water, or vitamins, as independent of the assistance derivable from their associates in the maintenance of digestive and nutritional harmony. No doubt some of these have special relations to others, as for instance that of iodine to fats, that of vitamin B to carbohydrates, that of vitamin A to lipoids, calcium and phosphorus holding substances, and that of vitamin C to inorganic salts. But whatever be their special relations to one another they are all links in the chain of essential substances requisite for the harmonious regulation of life's processes; if one link be broken, the harmony ceases or becomes discord."