PROTEIN REQUIREMENT IN THE DIETARY 581 



that which would, in the absence of the overflow, be necessary for this 

 purpose. In order to establish the adequacy of a maintenance-income 

 of protein for growth it would be necessary to show that the rate of 

 exogenous metabolism, which appears to be governed, at least in part, 

 by the Thyroid, is reduced when tissue-accretion occurs. The experi- 

 mental indications are quite the reverse and tend to show that tissue- 

 accretion is not a cause, but may be a consequence of lowered exogenous 

 metabolism. 



It is clear, however, that adults may maintain themselves in nitrog- 

 enous and calorific equilibrium upon a much lower protein intake than 

 is customary in many countries, and the question therefore arises 

 whether a restriction of the protein intake, particularly in the English- 

 speaking countries, may not be nationally and economically desirable. 

 We should be cautious in deciding this question upon an insufficiency 

 of evidence. A multitude of factors enter into the question besides 

 the merely financial factor. In the first place it may be stated that 

 no harmful effect of a high protein diet in normal persons has ever been 

 demonstrated. No particular disease is noticeably more common 

 among people accustomed to a high protein intake than among those 

 accustomed to a low protein intake. On the contrary diseases traceable 

 to lowered resistance of the peripheral tissues, such as Trachoma, are 

 decidedly more abundant among people whose diet is deficient in 

 protein, although it must be admitted that the dietary of these peoples 

 is probably deficient in other respects beside that of protein-content. 

 A high protein intake does not throw a "load upon the kidneys" which 

 is deleterious in normal persons, and in any case the "load" is very 

 easily lightened by a copious intake of water. 



On the other hand, taking Australia as an extreme instance of a 

 community which is accustomed to a high protein intake, we find from 

 the pre-war statistics of the Commonwealth Government that the 

 Death-rate was extraordinarily low, nearly one-half that which prevailed 

 in Italy and Austria, lower in fact than in any other country excepting 

 New Zealand, which is also a community of high protein consumption. 

 The Cancer death-rate was intermediate between that of Italy and that 

 of France, two communities each consuming far less meat per capita 

 than the Australian. 1 The birth-weight of Australian infants of British 

 parentage exceeds that of British infants born in England by over ten 

 ounces. 2 No trace of deleterious influence of the high proportion of 

 meat in the dietary is thus perceptible. On the other hand the diver- 

 sity of climatic and social and economic conditions forbids us from 

 drawing the opposite conclusion that the high protein intake is posi- 

 tively beneficial. 



It may be pointed out, however, that an unusually low, and also an 

 exceedingly high rate of Exogenous Metabolism are alike deleterious to 



1 Official Year-book of the Commonwealth of Australia, 1914. 



2 T. Brailsford Robertson: University of California Publications, Physiology, 1915, 

 4, p. 207. Amer. Jour, of Physiol., 1915, 37, p. 1. 



