CHEMISTRY AND FOOD 259 



elements and vitamins are at least equally important in 

 this connection. 



Taking account of energy values, protein content, 

 mineral elements, and vitamins, we now group the chief 

 articles and types of food according to their outstanding 

 nutritional characteristics as follows: 



1. Grain products economical sources of energy and 

 protein but not satisfactory in their mineral and vitamin 

 content. 



2. Sugars and fats chiefly important from the nutri- 

 tional standpoint as supplementary sources of energy, 

 although some fats are also important as sources of the 

 fat-soluble vitamin. 



3. Meats, including fish and poultry rich in protein 

 or fat or both, but showing, in general, the same mineral 

 and vitamin deficiencies as do the grains. 



4. Fruits and vegetables varying greatly in their 

 protein and energy values but very important as sources 

 of mineral elements and vitamins. 



5. Milk important as source of energy, protein, 

 mineral elements, and vitamins; the most efficient of all 

 foods in making good the deficiencies of the grains and 

 in ensuring the all-round adequacy of the diet. (See 

 Fig. 6.) 



Fruits, vegetables, and milk are now seen to have 

 much higher food values than were hitherto known, be- 

 cause they serve (as meats, sweets, and most fats do not) 

 to make good the mineral and vitamin deficiencies of the 

 breadstuff's and other grain products. 



What we now call the newer knowledge of nutrition 

 has been acquired within much less than a generation 



