VITAMINS 



237 



important role played by nicotinic acid, or nicotinamide, in many, if not 

 all, living cells. 



Prevalence of nicotinic acid deficiency 



Next to rickets, pellagra is probably the most common vitamin de- 

 ficiency disease in the United States. Although doubtless occurring prior 

 to the twentieth century, it was not recognized here until about 1907 or 

 1908. The disease is confined largely to the southern states where the 

 diet of the poorer classes is derived chiefly from corn meal, molasses, and 

 fat pork. The United States Public Health Service estimated that in 

 1929 there were 200,000 cases of pellagra in the country. In 1930 pellagra 

 was reported to have caused 7146 deaths, of which 98 per cent were 

 in the cotton belt. In contrast to the above figures, there were reported 

 in 1940 only 8688 cases of pellagra. Pellagra also occurs in Egypt, 

 Rumania, and South Africa, always in areas where corn is a main article 

 of diet. Over 1000 cases annually were reported in South Africa during 

 1944-1947. 



Symptoms of niacin deficiency in animals are relieved by administer- 

 ing tryptophan, and it is now known that tryptophan can be converted 

 into nicotinic acid in the animal body (p. 347). Since corn contains 

 little tryptophan, this relationship helps to explain why pellagra develops 

 especially among corn-eating populations. It has been suggested also 

 that corn may contain an antivitamin (p. 256) antagonistic to niacin. 

 In addition to these complicating factors, it is probable that pellagra 

 also involves deficiencies of other vitamins besides niacin. Nearly all 

 cases of pellagra require treatment with thiamine and riboflavin, in addi- 

 tion to nicotinic acid, in order to clear up all of the symptoms, and some 

 have also been reported to benefit from the use of pyridoxine. For this 

 reason it is very probable that the pellagra problem cannot be solved 

 by the use of nicotinic acid alone, but that the answer lies much more 

 in a general improvement of the diet. It is probable that this deficiency 

 disease will not be eradicated in the South until the prevailing diet of 

 corn bread, molasses, and fat meat is properly supplemented. This con- 

 stitutes an economic problem, since practically all potent sources of 

 the vitamin are relatively expensive foods, which the poorer classes are 

 unable to buy. 



Chemical nature 



Nicotinic acid is a relatively simple derivative of pyridine and possesses 

 a structure represented by the accompanying formula. The correspond- 

 ing amide is also effective as a vitamin: 



