302 ISIDOK GREENWALD 



made to point out certain properties common to all or most of such diets, 

 to discuss the significance of the differences and to indicate wherein the 

 evidence shows some of the diets to be inadequate. Finally, the question 

 of a possible improvement in our dietary habits will be discussed and the 

 various measures proposed for this purpose will be considered. 



Criteria of Adequacy of Diet. It is obvious from the preceding chap- 

 ters that the adequacy of a diet may be judged from many different 

 aspects; energy yield, nature and amount of protein, nature and content 

 of inorganic material, etc. Probably, the most essential of these is energy 

 yield. Unless the diet be restricted to a certain few materials, it is, if 

 sufficient in energy yield, sure to contain a considerable, even if not en- 

 tirely adequate, amount of protein, inorganic matter, etc. However, it 

 should be clearly recognized that this primacy of energy requirement may 

 be due largely to the fact that our means for determining the energy 



TRILLION CALORIES 

 100 200 300 400 500 600 TOO OOP ^00 



RlCE 



POTA TOE 5 

 3EEF, PORK AMD MUTTON 



Chart I. Total food value of the chief world foods expressed in calories. Rice, 

 wheat and sugar are practically all consumed as human food. Some of the rye and 

 barley is distilled or used for animal food. A considerable part of the potato crop 

 is used for industrial purposes. Data from G. K. Holmes, The Meat Situation in the 

 United States, Dept. of Agriculture, Office of the Secretary, Report No. 109. Figure 

 from G. B. Roorbach, The World's Food Supply, Proceedings of the American Philo- 

 sophical Society, Philadelphia, 1918, Vol. 57, pp. 1-33. 



content of the food and the energy requirements of the body are the better 

 developed. It may yet be found that man's desire for food is directed 

 primarily to securing, not a sufficient supply of energy, nor even of pro- 

 tein, but perhaps of some inorganic constituent or of some as yet unknown 

 or imperfectly recognized organic substance of the kind variously known 

 as vitainines, protective substances, food hormones, etc. Thus Osborne 

 suggested that the beneficial results of exercise may be due, in part, to 

 the ample supply of these substances secured as a consequence of the 

 hearty appetite thus produced. But, for the present, we will consider 

 food primarily as a supplier of energy, then of protein and only secon- 

 darily of other constituents. 



Relative Importance of Certain Foods. The amount of energy con- 

 tributed annually to the world's food by the more important food materials 



