PROTEIN METABOLISM 477 



Ikis ;iii iiiiiisiKill) i:ij)icl rate ol growth and range Itom O.G to about 

 2 lb. daily. The Aj^peiulix suininarizes the iletails for man, cattle, 

 horses, sheep, swine, chickens, and turkeys. In certain cases the 

 allowances are expressed as percentages o[ the ration, which in part 

 compensates for differences in body weight since larger individuals 

 normally eat more. 



Starvation is the state arising from a lack or partial deficiency of 

 food. Some of the physiological changes are due at least in part to a 

 shortage of j)r<)tcin. Thus protein deficiencies are associated with 

 famines, in some areas of the world a more specialized situatioti is 

 common among people in the lowest economic groups. Although 

 the total looil intake is usually low, the protein levels are relatively 

 lower still, producing a disease called kwashiorkor with poor growtli, 

 anemia, lack of pigmentation, low blood-protein levels, diarrhea, 

 reduced pancreatic ftmction and intestinal digestion, fatty livers, and 

 wasting ending in death in 30 to 90 per cent of untreated children. 

 Although not limited to children, the disease is most common among 

 them because the additional needs for growth raise their relative pro- 

 tein requirements and because after breast feeding they may be given 

 only cereals such as taro, corn, and millet. 



Kwashiorkor is perhaps the most widespread nutritional disease 

 (other than starvation itself) now taking human lives. It is common 

 in tropical America, central and southern Africa, and India. Un- 

 fortunately, severe cases do not respond to the feeding of protein. 

 Body proteins are at such reduced levels that dietary proteins are not 

 digested and thus cannot be used effectively. However, the adminis- 

 tration of amino acids and protein hydrolysates is quite effective and 

 after a time these products may be replaced with ordinary proteins. 

 Since foods high in protein are normally the most expensive, the 

 problem is an economic one to a great extent. 



Nitrogen Balance 



As indicated earlier, erythrocytes, other cells, antl many body ])ro- 

 teins are continually being broken down. Part of the nitrogen present 

 is excreted as urea, bile pigments, and uric acid (or allantoin), and 

 as bacterial nitrogen in the feces. This loss cannot be continued 

 without replacement if the animal is to remain healthy. Hence a 

 normal individual must consume nitrogen equivalent to that excreted. 

 Daily fluctuations are probably not important, providing income and 

 outgo are equal over longer periods. When they are, the animal is 

 said to be in nitrogen balance, meaning that he eats the same amount 

 of nitrogen as the combined losses in urine and feces. 



