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 digtetic 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 161 grams of proteid, with carbohydrates and fats sufficient to make the total fuel value of the day's ration equal to 3476 calories. In Austria, farm laborers consumed daily 169 grams of proteid, with carbohydrates and fats sufficient to raise the fuel value of the food to 6096 calories.

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,1 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 crews2 have shown fairly high results. The Yale University crew, while at Oales 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 428 grams, with a total fuel value of 3325 calories.

1 Bulletin No. 149. Woods and Mansfield. Studies of the Food of Maine Lumbermen. U. S. Department of Agriculture, 1004.

2 Bulletin No. 76. Atwater and Bryant Office of Experiment Stations, U. S. Department of Agriculture, 1900