Food requirements - in other words, dietaries - have been the subject of a large amount of study. Several methods of inquiry have been used, perhaps the most common one being to determine what amounts of nutrients are actually being consumed by individuals or groups of individuals living under various conditions of age, environment, and activity. In this way there has been studied the food consumption of children, the two sexes, professional men and women, persons engaging in labor of unlike severity and persons living under varying environments or engaged in special occupations.

185. Method Of Study

The general procedure in these studies has been to weigh, and, as far as possible, analyze, the food materials purchased for the individual or group of individuals, and weigh and analyze all the un-consumed materials. The difference between the purchased food and that unconsumed represents what is actually eaten. In many cases, as for, instance, with meats bought in large bulk, the purchased materials have been assumed to have an average composition. In this manner a widespread study has been made of the dietaries of different classes of people in the United States where habit, inclination, the limitation of means, and a local food supply have had their full and unrestrained influence. Similar studies have been carried on in an extensive way by European investigators.

186. Standard Dietaries

Based upon the results of these observations, with possibly certain modifications indicated by general principles, the following so-called standard dietaries have been suggested which are given in terms of protein, carbohydrates, and fats, together with the aggregate energy of the nutrients in each dietary. The dietaries in Tables XXIV and XXV are a statement of food consumption, and not of the amounts of the nutrients digested.

In the table 1 immediately following may be found the standards suggested some years ago by European investigators: 1 "Chemistry and Economy of Food," Bul. 21, O.E.S., p. 210.

Table XXIV. European Standards For Daily Dietaries For People Of Different Classes