NICOTINIC ACID (NIACIN) 



coenzyme. Nicotinamide was also taken up, but nearly all in a form 

 that could be removed from the cells by repeated washings. ^^'* 



The nicotinic acid content of blood or plasma in pellagra was very 

 little different from that of controls,''^ nor did the coenzyme I content 

 of erythrocytes vary significantly in different stages of pellagra/^ 

 normal cells containing 85 fig. per ml. and cells from pellagrins 70 to 

 90 fjLg. per ml. This remarkable constancy in the amounts of nico- 

 tinic acid and its derivatives in blood, and the transitory nature of 

 the increase resulting from the administration of nicotinic acid or the 

 amide make the estimation of blood levels of no value in assessing 

 nutritional status, a.id it is generally agreed that the only satisfactory 

 method is one based on the excretion of nicotinic acid derivatives in 

 response to a test dose of the acid or amide (page 259). 



Nicotinic Acid Content of Other Body Fluids and Tissues 



Human milk is a poor source of nicotinic acid and contains less than 

 cow's milk (see page 233). According to A. Lwoff and his collabora- 

 tors, human milk contained only 0-07 /xg. of the amide per 100 ml. 

 (estimated microbiologically by means of Proteus) in the first three to 

 eight days after delivery, but after the third week this rose to o-i6 

 mg. per 100 ml."^^ At this stage, the requirements of the baby, 

 assumed to be 0-78 mg. per day, were satisfied by the ingestion of 

 500 ml. of milk per day, but subsequently the demands increased to a 

 level that could not be met solely by the amount present in the milk. 

 The amount of nicotinamide present in early milk could be increased 

 many-fold by giving a 600-mg. dose of the amide forty-eight hours 

 before delivery ; '^ for instance, when 600-mg. doses were given daily 

 for one month prior to delivery, the nicotinamide content of the milk 

 was increased to 0-07 mg. per 100 ml."^^ This would appear to be an 

 observation of considerable importance, as the human foetus has been 

 said to have no store of nicotinamide ; ^^ this assertion must be 

 accepted with reserve, however, for it has been shown that blood from 

 the umbilical cord contains as much nicotinic acid as the maternal 

 blood. '5 



Coryell et alJ^ found that the amount of nicotinic acid secreted in 

 the milk during twenty-four hours increased from 0-04 mg. on the 

 first day post partum to 2-94 mg. on the tenth day, the intake being 

 16-5 mg. per day. The amount secreted in the mature milk varied 

 from 0-52 to 2-02 mg. per day. Earlier results, in which the nicotinic 

 acid content was expressed in mg. per 100 ml., were 0-245 for tue 

 amount secreted on the tenth day and 0-176 to 0-196 mg. per 100 ml. 

 for the mature milk. Of the ingested nicotinic acid, 7 % appeared in 

 the milk and 3 % in the urine. 



264 



