266 SCIENCE REMAKING THE WORLD 



The basal principles to which I refer may be sum- 

 marized rather briefly. 



First, food is fuel. Like coal the amount of energy 

 that a given food will produce can be measured in heat 

 units and that is all there is to the calorie evaluation 

 idea. The calorie is simply a unit to measure with, like 

 the inch or the centimetre. Thanks to accurate instru- 

 ments and chemical analyses, it is now easily possible to 

 determine on the one hand just how many calories of 

 energy you or I need to run our human machine for 

 twenty-four hours, and on the other hand just how much 

 of the various kinds of foods we must consume to pro- 

 duce these calories. 



But even though a foodstuff measures up to our 

 calorie needs the body requires other qualities. To 

 produce energy alone we can use starches, sugars, or 

 fats, but to rebuild the living cellular matter (proto- 

 plasm) we require not only these foods but also others 

 rich in nitrogen. The chemist calls starches and sugars, 

 "carbohydrates." He calls the fatty substances, 

 "lipins," and to the nitrogenous foodstuffs he has ap- 

 plied the term "protein." For all of these collectively 

 he uses the term "organic nutrients." Chemical analy- 

 ses easily give the proportions of carbohydrates, fats, 

 and proteins in any foodstuff and this information is 

 now available to the public in the form of tables issued 

 by the Government and to be found in the many 

 standardized texts on dietetics. If the ordinary in- 

 dividual will so select his foodstuffs as to provide fifty 

 grams (about two ounces) of protein per day and to 

 meet the calorie needs, he has satisfied most of what we 



