NUTRITION 237 



In the second place, the larger protein diet with its in- 

 crease of protein wastes in the body itself (as contrasted 

 with the alimentary canal) involves a greater burden on the 

 organs of excretion. This burden may fall not alone on the 

 kidneys, which finally discharge these wastes from the body, 

 but also upon other organs in which the waste products are 

 prepared for final removal from the blood by the kidneys. 

 Convincing proof has, however, not been given that these 

 organs, when in a healthy condition, are injured by the work 

 of caring for more than the waste of a low protein diet. 

 A somewhat analogous case is that of muscular activity. 

 This, too, must be limited or even given up altogether in 

 some diseased conditions lest some undue burden be placed 

 upon the organism ; but in health the body is actually bene- 

 fited by the " burden " of even vigorous muscular activity. 



The further question then arises whether there is any 

 possible advantage in a liberal protein diet. It is certainly 

 not needed for power or for fuel; it may, however, be plau- 

 sibly urged that thereby we insure an abundance of each 

 amino-acid needed for the formation of the innumerable 

 products of chemical manufacture in the body. When an 

 engineer builds a bridge, he does not build it just strong 

 enough to sustain the expected load ; he allows a liberal 

 " margin of safety." Similarly, it is not a desirable economic 

 condition when one's income each week is just enough to 

 meet necessary expenses, for this does not allow for the 

 unexpected emergency which we cannot foresee. So it has 

 been urged and, it would seem, reasonably urged that it is 

 better not to diminish protein intake, as a rule, to the irre- 

 ducible minimum of 40 to 50 grams daily. While 100 to 150 

 grams is almost certainly far more than is necessary to secure 

 the proper margin of safety, it may well be wiser to use 20 

 or more grams above the minimum ; that is to say, a protein 

 intake of 70 grams corresponds with what, in the present state 

 of our knowledge, may be regarded as a conservative estimate. 



