Energy Needs of Different Workers We should expect that a person 

 working in the steel mills expends more energy than a clerk who sits at a 

 desk making out payrolls. The energy needs for various kinds of work are 

 given in the table below, which combines the results of many studies. Men 

 and women of above-average weight require more than indicated ; similarly, 

 men and women of light weight need less. 



Energy Needs and Kinds of Work^ 



Building Stuff Like all other living animals, the human organism 

 needs proteins and minerals out of which protoplasm develops new tissues 

 (see pages 96-97). The body makes use of a wide variety of proteins, al- 

 though some are more completely used than others. Proteins differ in the 

 proportions of the amino-acids they contain (see page 97). The combination 

 of amino-acids found in the protoplasm of any species differs somewhat 

 from that found in other living things. Those proteins which are most like 

 human protoplasm are most usable in the growth of new body tissues. 



The mineral needs of the body are also essentially the same as those of 

 other animals. It is significant that a newly born child is relatively poor in 

 calcium and rich in iron. Furthermore, the skeleton, composed largely of 

 calcium and phosphorus (see page 100), gets most of its growth during the 

 first eighteen years of life. Nearly one third of the phosphorus found in 

 the body is in the muscles and other soft tissues, which also develop rapidly 

 during the first years of life. Thus growing children require relatively more 

 calcium and phosphorus than adults. Although the iron in the body is but a 

 small quantity, its function in respiration does not permit a shortage (see 

 page 101). Some diets are inadequate in this respect. 



^Hazel K. Stiebeling and E. F. Phipard, Diets of Families of Employed Wage Earners 

 and Clerical Workers in Cities, United States Department of Agriculture Circular No. 507, 

 1939. 



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