CHAPTER XIII 

 A STUDY OF FOODS AND DIETARIES 



Problems: A study of foods to determine: 

 (a) Their nutritive value, 

 (h) The value of vitamins. 



(c) The relation of work, environment, age, sex, and digestibility 

 of foods to diet. 



(d) The relative cheapness of different foods. 



(e) The daily calorie requirement. 



Laboratory Suggestions 



Laboratory exercise. Composition of common foods. The series of food 

 charts suppHed by the United States Department of Agriculture makes an 

 excellent basis for a laboratory exercise to determine common foods rich in 

 (a) water, (5) starch, (c) sugar, (d) fats or oils, (e) protein, (f) salts, {g) refuse. 

 New charts on vitamins made by American Medical Association. 



Demonstration. Method of using bomb calorimeter. 



Laboratory and home exercise. To determine the best balanced dietary for 

 yourself (using standard of Atwater, Chittenden, or Voit) as determined by the 

 use of the 100-calorie portion. 



Why we need Food. — A locomotive engine takes coal, water, 

 and oxygen from its environment. A living plant or animal gets 

 food, water, and oxygen from its environment.^ Both the living 

 and the non-living machine do the same thing with this fuel and 

 part of this food. They oxidize it and make use of the energy 

 thus released. But the living organism in addition may use food 

 to repair parts that have broken down, or even to build new 

 parts. Thus food may he defined as something that can he used by 

 the body of a plant or animal to release energy, or that forms mate- 

 rial for the growth or repair of the body of a plant or animal. The 



^ Animals and some plants get organic food from their environment ; but green 

 plants, as we have seen, make their organic food from materials which they get 

 from their environment. 



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