Topics: Dietetic customs of mankind. Origin of dietary standards. True food requirements. Arguments based on custom and habit. Relationship between food consumption and prosperity. Erroneous ideas regarding nutrition. Commercial success and national wealth not the result of liberal dietary habits. Instinct and craving not wise guides to follow in choice and quantity of food. Physiological requirements and dietary standards not to be based on habits and cravings. Old-time views regarding temperate use of food. The sayings of Thomas Cogan. The teachings of Cornaro. Experimental results obtained by various physiologists. Work of the writer on true proteid requirements. Studies with professional men. Nitrogen equilibrium with small amounts of food. Sample dietaries. Simplicity in diet. Nitrogen requirement per kilogram of body-weight. Fuel value of the daily food. Experiments with university athletes. Nitrogen balance and food consumption. Sample dietaries. Adequacy of a simple diet.

Having acquired information regarding the principles of metabolism and the general laws governing the nutrition of the body, we may next consider briefly the dietetic habits of mankind, with a view to learning how far such habits coincide with actual nutritive requirements. Eventually, we shall need to ask the questions: What are the true nutritive requirements of the body? How much food and what kinds of food does the ordinary individual doing an average amount of work need each day in order to preserve body equilibrium, and to maintain health, strength, and vigor under the varying conditions of life? What amount of nitrogen or proteid, and what the total calorific value required to supply the physiological needs of the body? How closely do the so-called “normal diets” and “standard diets,” which have met with such general acceptance, conform to a rational conception of true physiological needs? These are vital questions of great physiological and economic importance, and they are not easily answered; but theoretical considerations based on scientific data, and experimental evidence combined with practical experience, should point the way to some very definite conclusions.

Observations made in many countries regarding the dietetic customs and habits of the people have resulted in the establishment of certain dietary standards, which have been more or less generally adopted as representing the requirements of the body. As a prelude to the discussion of this question, let us consider briefly some of the results of these dietary studies. In Sweden, laborers doing hard work were found by Hultgren and Landergren to consume daily, on an average, 189 grams of proteid, 714 grams of carbohydrate, and 110 grams of fat, with a total fuel value for the day’s ration of 4726 large calories. In Russia, workmen at moderately hard labor, having perfect freedom of choice in their food, were found by Erisman to take daily 132 grams of proteid, 584 grams of carbohydrate, and 79 grams of fat, this ration having a fuel value of 3675 calories. In Germany, soldiers in active service consumed daily, according to Voit, 145 grams of proteid, 500 grams of carbohydrate, and 100 grams of fat, with a fuel value of 3574 calories. In Italy, laborers doing a moderate amount of work were found by Lichtenfelt to consume daily 115 grams of proteid, 696 grams of carbohydrate, and 26 grams of fat, with a fuel value of 3655 calories. In France, Gautier states that the ordinary laborer working eight hours a day must have 135 grams of proteid, 700 grams of carbohydrate, and 90 grams of fat daily, with a fuel value of 4260 calories. In England, weavers were found to take daily 151 grams of proteid, with carbohydrates and fats sufficient to make the total fuel value of the day’s ration equal to 3475 calories. In Austria, farm laborers consumed daily 159 grams of proteid, with carbohydrates and fats sufficient to raise the fuel value of the food to 5096 calories.

Subjects.Proteid consumed
Daily.		Total Fuel Value
of Daily Food.
gramscalories
Swedish laborers, at hard work1894726
Russian workmen, moderate work1323675
German soldiers, active service1453574
Italian laborers, moderate work1153655
French laborers, eight hours’ work1354260
English weavers1513475
Austrian farm laborers1595096
American Subjects.
Man with very hard muscular work1755500
Man with hard muscular work1504150
Man with moderately active muscular
work		1253400
Man with light to moderate muscular
work		1123050
Man at “sedentary” or woman with
moderately active work		1002700

Observations of this order might be multiplied indefinitely, but the above will suffice to give a general idea of the average food consumption of European peoples doing a moderate amount of work. These data, however, must be supplemented by the observations made in our own country, which have been very extensive, through the “investigations on the nutrition of man in the United States,” carried on by the Office of Experiment Stations in the Department of Agriculture, under the efficient leadership of Atwater. As stated by Messrs. Langworthy and Milner, in an official bulletin issued in 1904, dietary studies of the actual food consumption of people of different classes in different parts of the United States have been made during the years 1894 to 1904 on about 15,000 persons,—men, women, and children,—as a result of which it is indicated that “the actual food requirements of persons under different conditions of life and work” vary from 100 to 175 grams of proteid per day, with a total fuel value ranging from 2700 to 5500 calories. For comparison, the various data may be tabulated as shown on page [155].

These figures by no means represent maximum food consumption. Thus, studies have been made on fifty Maine lumbermen,[53] where the intake of proteid food averaged 185 grams per day, with a total fuel value of 6400 calories. Further, dietary studies of university boat crews[54] have shown fairly high results. The Yale University crew, while at Gales Ferry, averaged per man during seven days 171 grams of proteid, 171 grams of fat, and 434 grams of carbohydrate, with a total fuel value of 4070 calories per day. The members of the Harvard University crew showed an average daily consumption of 160 grams of proteid, 170 grams of fat, and 448 grams of carbohydrate, with a total fuel value of 4074 calories. It is also reported that a football team of college students in the University of California consumed daily, per man, 270 grams of proteid, 416 grams of fat, and 710 grams of carbohydrate, with a total fuel value of 7885 calories. These figures may be contrasted, however, with the data obtained in a study of the dietary habits of fourteen professional men’s families, where the average amount of proteid consumed daily was 104 grams, fat 125 grams, and carbohydrate 423 grams, with a total fuel value of 3325 calories.

Leaving out of consideration the extremes given, it is undoubtedly true that, within certain rather wide limits, there is an apparent tendency for people of different nations, having a free choice of food and not restricted by expense, to consume daily approximately the same amounts of nutrients; to use what may be called liberal rather than small amounts of food; and, lastly, to consume food somewhat in proportion to the amount of work done. It is perhaps, therefore, not strange that students of nutrition should have taken these results, obtained by the statistical method, as indicating the actual needs of the body for food, and that so-called “standard diets” and “normal diets” should have been constructed, based upon these and corresponding data. Thus, we have the widely adopted “Voit standard,” composed of proteid 118 grams, carbohydrate 500 grams, and fat 56 grams, with a total fuel value of 3055 calories, as the amount of food required daily by a man of 70 kilos body-weight doing a moderate amount of work. These figures were obtained by Voit as an average of the food consumption of a large number of laboring men in Germany, and they carried additional weight because at that time Voit and others thought they had evidence that nitrogenous equilibrium could not be maintained for any length of time on smaller amounts of proteid.

The figures given in the preceding table under the head of American subjects constitute the “Atwater standards,” and as already indicated, are based upon the dietetic habits of over 15,000 persons under different conditions of life and physical activity. In the words of the official Bulletin, these standards covering the quantities of food per day “are intended to show the actual food requirements of persons under different conditions of life and work.” Here, however, lies an assumption which seems to meet with wide acceptance, but for which it is difficult to conceive any logical reason. The thousands of dietary studies made on peoples all over the world, affording more or less accurate information regarding the average amounts of proteid, fat, and carbohydrate consumed under varying conditions, are indeed most interesting and important, as affording information regarding dietetic customs and habits; but, the writer fails to see any reason why such data need be assumed to throw any light on the actual food requirements of the body. In the words of another, “Food should be ingested in just the proper amount to repair the waste of the body; to furnish it with the energy it needs for work and warmth; to maintain it in vigor; and, in the case of immature animals, to provide the proper excess for normal growth, in order to be of the most advantage to the body” (Benedict).

Any habitual excess of food, over and above what is really needed to meet the actual wants of the body, is not only uneconomical, but may be distinctly disadvantageous. Voit, among others, has clearly emphasized the general principle that the smallest amount of proteid, with non-nitrogenous food added, that will suffice to keep the body in a state of continual vigor is the ideal diet. My own conception of the true food requirements of the body has been expressed in the statement that man needs of proteids, fats, and carbohydrates sufficient to establish and maintain physiological and nitrogen equilibrium; sufficient to keep up that strength of body and mind that is essential to good health, to maintain the highest degree of physical and mental activity with the smallest amount of friction and the least expenditure of energy, and to preserve and heighten, if possible, the ordinary resistance of the body to disease germs. The smallest amount of food that will accomplish these ends is, I think, the ideal diet. There must truly be enough to supply the real needs of the body, but any great surplus over and above what is actually called for may in the long run prove an undesirable addition. With these thoughts in mind, may we not reasonably ask why it should be assumed that there is any tangible connection between the dietetic habits of a people and their true physiological needs?

Arguments predicated on custom, habit, and usage have no physiological basis that appeals strongly to the impartial observer. Man is a creature of habits; he is quick to acquire new ones when his environment affords the opportunity, and he is prone to cling to old ones when they minister to his sense of taste. The argument that because the people of a country, constituting a given class, eat a certain amount of proteid food daily, the quantity so consumed must be an indication of the amount needed to meet the requirements of the body, is as faulty as the argument that because people of a given community are in the habit of consuming a certain amount of wine each day at dinner their bodies must necessarily be in need of the stimulant, and that consequently alcohol is a true physiological requirement. A large proportion of mankind is addicted to the tobacco habit, and to many persons the after-dinner cigar is as essential to comfort as the dinner itself; but would any one think of arguing that tobacco is one of the physiological needs of the body?