The human body, as far as can be judged, does not use one nutrient to the exclusion of another, but science has proved that the best results are obtained from diets balanced to suit the needs of the body, providing the fuel and repair materials in the amounts which are calculated to give the maximum value with the minimum expenditure on the part of the organism.

For while no two individuals are exactly alike, there are factors which govern or influence the food requirements of all, and thus make it possible to estimate the needs of the body with a fair degree of accuracy.

It has been found, by means of calorimeter experiments (direct and indirect), that a certain amount of heat is produced within the body, regardless of external movement or food; that is, when a body is lying absolutely quiet with no movement save that of breathing, the internal work of the organism, which is continuous, releases so much heat, and this is produced whether there is food to replace it or whether the body structure is burned. This is known as the basal rate of metabolism, and constitutes the normal basal requirements. Any external movement will increase this rate; the greater the activity the higher the increase. Consequently external work calls for food in addition to that which is used to run the engine, in order to save the body from destruction.

DuBois[20] finds “Basal Metabolism above normal in exophthalmic goiter, in fevers, in lymphatic leukemia, and in pernicious anemia, in severe cardiac disease, and in some cases of severe diabetes and cancer; it is lower than normal in cretinism, and in myxedema, in old age, in some wasting diseases and perhaps in some cases of obesity.” This fluctuation in the Basal Rate of metabolism furnishes a factor in the diagnosis of disease, not only recognized but coming more and more in use.

FACTORS DETERMINING THE FOOD REQUIREMENTS OF THE BODY

For the Adult.—Muscular activity, Age and Size, are most important factors influencing the food requirements. The physical condition and environment of the individual also exert a certain amount of influence upon the intake of food.

Work.—Muscular activity, as already stated, increases the body expenditures; consequently the more active the work the greater amount of energy food needed per unit of weight.

Age.—As the individual grows older, the rate of metabolism decreases until, in old age, it is not more than a third to a fifth of what it was in earlier life. This is due to a general “slowing down” of the machinery, the heart does not beat so rapidly, nor is the respiration so quick. The digestive organs, the heart, the liver, and the kidneys, cannot handle the volume of food which was required during the period of greatest physical activity. Hence, any great excess over and above that which is needed for the maintenance of the body in health will be a source of danger to the elderly person. Von Noorden claims the food requirements of individuals from

Sex.—Science has proved, that there is little difference in the food requirements of men and women, provided they are alike in age, weight and size, and are doing the same amount and type of work. But women, as a rule, weigh less than men, hence their food requirements are approximately less.

Murlin finds the food requirements of pregnant women to be some what higher than of non-pregnant ones, and the requirements of the nursing mother to be higher than either (see chapter on Pregnancy and Lactation).

For the Child.—The factors influencing the food requirements are different, to a certain extent, from those of the adult. The main difference lies in the fact that the adult needs food only for the maintenance and repair of the body, while the child must have food, not only to cover its maintenance requirements, but to support the growth and development which should be continuous from birth to maturity. Resistance, too, must be developed during this period in order to safeguard the child through life.

The rate of metabolism in the infant is greater than at any other period of life, consequently, even if a child were one-third the weight of its parent, it would inevitably cease to grow and would become malnourished, if its food requirements were reckoned at only one-third that of the parent.

Adjusting the Food Requirements.—Taking these factors as guides for estimating the food requirements of man, it is evident that no hard and fast law can be laid down to cover all, that each individual must adjust the food intake according to the weight and activity of the body. Sherman has arranged the following table showing the energy expenditures per hour for the average man (154 pounds), per pound of body weight (these are approximate averages only).

TABLE[21]

The above table, calculated for an average man weighing 154 pounds, may seem less simple to use than one based on the energy requirements per pound of body weight per hour, of an average individual. For example, a man weighing 123 pounds and performing practically the same amount and type of work as done by the man weighing 154 pounds would require practically one-fifth less calories than the latter individual. Hence, to facilitate the estimation of the food requirements for average individuals, the following table is included.[22]

Possibly a few explanatory words, as to the terms used in the above tables, will assist the nurse in making the necessary calculation. “Sleeping quietly” makes allowance for no movement save that of respiration; any undue restlessness will call for an increase in the above allowance. “Sitting at rest” includes the time spent at meals, sitting in class room, ward office, studying or reading. It does not include much walking about the room, rising frequently, or nervous restlessness.

“Light exercise” includes all light house work, running an ordinary sewing machine, walking about office or ward, (receiving ward included). It does not include washing, sweeping or scrubbing.

“Active exercise” includes washing, sweeping, scrubbing, general house work, carpentry, and such sports as tennis, basket ball, and ordinary gymnasium work.

“Severe exercise” includes road workers (working with pick and shovel) fast running, baseball, football, and swimming.

“Very severe exercise” includes the work done by miners, handling of freight, and lumbermen, especially those working in extreme cold, where the severe cold makes extra demands on the fuel supply. By making use of the averages just mentioned it should be a simple matter to calculate the food requirements of any normal individual. It is necessary to know the weight of the person in question, and the manner in which the twenty-four hours are spent, and, in the case of elderly individuals, make the reductions believed to be necessary for health.

Method of Using the Tables.—Let us take a nurse in training for this purpose. Suppose the nurse weighs 110 pounds, and spends the twenty-four hours as follows,

Her daily food requirements would probably be approximately 2,235 calories. This estimate would be increased, if she were obliged to do much heavy lifting, scrubbing of beds, or other duties requiring the expenditure of much effort. It would be decreased if the hours spent in study and class room work were increased and the hours on the ward shortened. The estimation may be made as follows,

This estimate may be made to suit any individual, the man in the office or the one working on the streets, the woman living at home or the one spending eight or ten hours scrubbing the floors of a great office building; it is simply a matter of adjusting the calories in the dietary to meet the requirements of body weight and muscular activity.

Energy Requirements for Children.—In estimating the energy needs of children, the above method is not satisfactory, since the storage of material for growth must be considered, as well as the activities of the body. The growth period includes the years from birth to the eighteenth year, after which time the food requirements of the body are made on a basis of weight and muscular activity, as in all adults. The table on the following page shows the food allowances made for healthy children; in the feeding of malnourished or underweight children, more food in proportion to age is given in order to overcome the handicap under which they are suffering.

Food Allowances for Healthy Children[23]

Calories per Pound of Body Weight per Day.[24]

Children, like adults, differ in degrees of activity; that is, one child may be very active, running and playing more strenuously than another. Hence a margin of safety must be allowed to cover the energy expenditures of the more active child, to safeguard it against becoming malnourished.

To facilitate the computation of the food requirements of children a schedule showing the number of calories per pound of body per day is included on opposite page.

The food requirements are such as to allow of a steady increase in the weight and stature of the child; the rate of gain for normal children should be as follows:

Average Rate of Gain per Week, for Normal Children

The averages just given are for healthy children; those who are underweight for their age and height should show a more rapid increase in weight with an increased food allowance. It must also be remembered that a simple gain in weight is not sufficient evidence of a child’s normality; a freedom from gastro-intestinal disturbances, and a resistance to disease, are equally essential.

There have been tables arranged to show the proper weight for height for boys and girls of different ages (see appendix). These are valuable since, by their use, attention is called to the child who is not up to the average. Medical examination of such children frequently shows reason for their underweight, and measures may be instituted which may save the child from a lifetime of poor health.

Dr. Pirquet has arranged a scale (Pelidisi Chart) showing the state of nutrition in children, based upon the sitting height (in centimeters), to weight (in kilograms). See appendix.

PROTEIN REQUIREMENTS

There is never a period in life in which protein is not needed. During the early years it is essential that the proteins, or at least a goodly portion of them, be obtained from animal sources, milk and eggs in particular; when cereals and legumes (beans and peas) are used to provide for the protein requirements, they must be supplemented by milk or eggs (or both), in order that the growth and development of the child may proceed at a normal rate.

Adults require protein for the repair of old tissues and to furnish material for the building of new cells, and again it is believed advisable to have at least a portion of this protein from animal sources, milk, meat or eggs.

MINERAL REQUIREMENTS

Just as energy foods and proteins must be adjusted in the dietary to safeguard the health of the body, so the mineral salts must be adjusted for a like purpose. Studies made of the dietaries of a number of families brought to light the fact that the children more often suffered from a deficiency of calcium, phosphorus and iron in their diets than they did from too little protein,[25] proving that it is quite as essential to adjust the mineral salts in the diet as it is that of the organic constituents.

According to Sherman the diet of an adult should contain each day per pound of body weight:

These averages, while covering the needs of the mature body, do not furnish the necessary amount of protein, or mineral salts to support the growth and development of the child. Hence, it has been deemed advisable to reckon the requirements of the latter per thousand calories, instead of per pound of body weight, in this way obviating some of the danger of protein and mineral deficiencies.

McCollum, Simmonds and Pitz have shown that a deficiency in the inorganic content of a diet may result in a retarding or suspension of growth. This result has been overcome on the introduction of the proper mineral salts into the diet. This salt mixture is such as to make the total ash, approximate that found in the composition of milk ash.

The following diagram illustrates this point.

Effect upon growth of adding to a diet otherwise adequate a salt mixture of such composition as to make the composition of the total ash similar to that of milk ash; immediate resumption after entire suspension of growth. Courtesy of Dr. E. V. McCollum. The following outline will serve as a guide in making the estimates for the food requirements of children:

The Diet of a Child Should Contain for Every 1000 Calories Furnished by the Foodstuffs,

Vitamine Needs.—We have seen the manner in which the energy and protein foods have been adjusted in the diet, but these can not alone assure the body, and especially the growing body of a normal maintenance and repair of its tissue, or support the growth which is essential at this time. This function is believed to belong to the vitamines, since feeding experiments have demonstrated the fact that animals soon cease to grow, develop deficiency diseases, and finally die, when deprived of the essential constituents. Gillett advises, as a safe rule, the use of one, and preferably two foods known to be rich in the fat soluble vitamine, in each day’s food allowance, milk and leafy vegetables, for example. If the foods containing phosphorus, calcium, and iron are taken in sufficient quantity, the second, or “B” vitamine needs, will probably be adequately covered, but the presence of the “C” vitamine must be carefully attended to; some fresh fruit or vegetables (see table) is obligatory each day to insure the individual against the development of scurvy.

Factors Affecting the Food Selection.—The estimation of the energy needs of the body, and the selection of the foods to furnish the fuel for this purpose, depend largely upon the individual. The digestion of the fats, as well as the way in which the body utilizes them, makes the use of this foodstuff more or less limited according to the ability of the individual to take care of them, the minimum allowance for children being between 2 and 3 ounces per day. According to Gillett, “If boys and girls get at least this amount from butter and its substitutes, cream, bacon, fat meat and oils, additional amounts from their food will provide a margin of safety, without overtaxing the digestive system.”

After determining the amount of fat required in each day’s food allowance, it is a simple matter to adjust the carbohydrates. It is safer from a health standpoint, to obtain the greater portion of this foodstuff from starchy foods rather than from the sugars, many foods rich in starch, likewise contain appreciable amounts of protein and fat, whereas sugar is practically one hundred per cent. carbohydrate. The ease, too, with which this substance ferments in the stomach, and the manner in which it destroys the appetite for other foods, makes the use of much of it in concentrated form unadvisable, especially in the diet of children.

The amount of sugar allowed each day, should be limited to an ounce or ounce and a half (2 to 3 tablespoonfuls), and a less quantity is desirable. In order to obtain the best results, with the least deleterious effect on the body, it is advisable to give sugar in dilute form. A piece of pure candy after a meal may not harm the child; but just before, or between meals, as well as the habit of making the breakfast cocoa and cereal of syrup-like sweetness is deplorable, and should in all instances be discouraged.

The American Red Cross recommends the following method for estimating the amount of sugar in the dietary: “Add one-half the weight of such foods as jellies, jams and preserves, and three-quarters the weight of such foods as candy, honey and syrup, to the weight of sugar used.” The amount of sugar consumed, as such, by the adult each day, is not of such paramount importance as it is in the case of children, but even for adults an excessive amount of carbohydrate in this form is not considered advisable from a health standpoint.

In order to assure each member of the family of getting all of the materials needed for the growth, repair and regulation of their bodies, as well as the necessary fuel material with which to run the engine and to maintain the proper body temperature, the following practical method is suggested for the planning of the daily dietary.

The Diet Each Day Should Contain:

1. Milk:

2. Cereals and Breadstuffs:

3. Meat or its Substitute:

4. Vegetables:

5. Fruit:

6. Desserts:

7. Fats:

Suggestions for Serving Meals.—After reckoning the number of calories needed for the day, it is well to remember that the protein must be adequate in type and amount; that there should be an abundant supply of vitamines and iron in each day’s ration; that milk should always be included in order to make sure of having a sufficient amount of calcium in the diet; that there should be only one heavy protein dish at any one meal, and that it is unwise to serve a meal in which the fluids predominate on account of their deficiency in energy and proteins.

If a meal is made up of the right kind of foods, in the proper proportion, and each individual eats sufficient to assure the maintenance of the normal weight, is free from gastro-intestinal disturbances, and shows a normal resistance to disease, it is more than probable that a sufficient quantity is being consumed each day.

All foods should be carefully selected, and properly prepared in order to derive the maximum benefit therefrom, and the regularity and attractiveness with which the meals are served have almost as much to do with the health and happiness of the individual, as the character of the foods included in the day’s dietary.

PROBLEMS