332 HOW DOES MAN DETERMINE THE VALUE OF FOOD? 



presence of minute quantities of these salts in the body. Thus 

 they act as regulators of bodily activity. 



Practical Exercises 2. From the charts given in any laboratory workbook, 

 determine the actual percentage of nutrients in beef, potatoes, oysters, and corn 

 meal. Do all foods have equal nutritive value ? 



From these charts make a table containing : 



(a) Five foods rich in protein (15 per cent or more). 



(6) Five foods rich in carbohydrates (50 per cent). 



(c) Five foods rich in fat (50 per cent or more). 



(d) Five foods having a high fuel value (1500 Calories or more per pound). 



(e) Five food substances that are over 50 per cent water. How would 

 water affect the cost of food, providing you had to pay for the water? 



(/) Two foods rich in mineral salts. 



In your opinion, which of the foods given are the best tissue-building 

 foods ? Remember that living matter is made up of carbon, oxygen, hydrogen, 

 nitrogen, sulphur, and a minute amount of mineral salts. Which do you con- 

 sider the best energy-producing foods ? Explain. 



Roughage. Certain parts of foods rich in carbohydrates, usually 

 the cellulose walls of plant cells, contain indigestible material 

 which is useful in stimulating the muscles in the large intestine 

 and thus causing the waste matter to be thrown off regularly. 

 This prevents constipation. Bran, whole wheat, fresh fruits, and 

 vegetables provide the best sources of these materials. 



Flavors and condiments. Most of us are aware that flavoring 

 materials such as pepper, mustard, and other condiments are not 

 true foods. While flavoring extracts, meat, and vegetable flavors 

 do not have food value, they are of great value in making the 

 food more appetizing and increasing the secretion of gastric juice. 



What are the essentials of an adequate food supply? One 

 writer has said that " an adequate food supply should include 

 (1) sufficient organic nutrients in digestible form to yield the 

 needed energy, (2) protein sufficient in amount and appropriate in 

 kind, (3) adequate amounts and proportion of various ash con- 

 stituents or inorganic foodstuffs, and (4) sufficient of each of essen- 

 tial vitamins." The problems which follow will help us to find 

 out just what this statement means. 



Self-Testing Exercise 



A food is anything that furnishes (1) and (2) or 



(3) up the body. Foods as purchased may contain waste, 



(4) (5), (6), and (7). The or- 



