FACTORS INFLUENCING B VITAMIN REQUIREMENTS 271 



of duplicate meals, of 24-hour collections of urine, and of fasting one- 

 hour samples of urine. During the period of lactation the thiamine intake 

 varied from 0.73 to 1.59 mg/day and the riboflavin intake from 2.2 to 

 3.6 mg/day. Sample data from one individual in which the average 

 thiamine intake was 1.11 mg/day and the average daily riboflavin intake 

 was 2.95 mg are given in Table 11. 



Table 11. Average Daily Secretion of Thiamine and Riboflavin in Hvn.an Milk. 



Total thiamine secretion in milk was from 2 to 12 per cent of the 

 intake, and total riboflavin, 6 to 32 per cent. For all subjects, the maxi- 

 mum daily thiamine secreted in milk never exceeded 15 per cent of the 

 intake and varied in urine from 2 to 57 per cent of the intake. Assuming 

 that there is no waste of thiamine in the production of milk by mammary 

 tissue, and since there was no indication of an avitaminosis in the sub- 

 jects, the authors conclude that a 15 per cent increase in the dietary 

 supply of the requirements of normal women supplied any increased 

 requirements due to lactation. On this basis the National Research 

 Council's recommendations of 3 mg of riboflavin per day and 2 mg of 

 thiamine per day on a 3000-Calorie basis seem adequate, and the absolute 

 requirement is obviously much lower. The National Research Council 

 also suggests 20 mg per day as a suitable nicotinic acid intake under 

 similar conditions. Their recommendations for lactation all involve an 

 increase of from one-half to one-third of the level (on a 3000-Calorie 

 basis) for a very active normal woman. 



Pathological States of the Body. It is readily apparent that a large 

 variety of pathological situations might arise which could hamper the 

 efficient utilization by the organism of an otherwise adequate B vitamin 

 supply. Some of these which occur with sufficient frequency to permit 

 their recognition as distinct clinical entities are discussed in later chapters 

 as deficiency conditions (Chap. VI C) . Many other clinical and acute 

 pathological conditions, however, appear only from time to time, and yet 

 effectively cause a distinct rise in B vitamin requirements. While such 

 conditions are of major importance in hospital dietetics, there is not at 

 present sufficient information to permit rational treatment in these cases. 

 Largely because of this, "shot-gun vitamin therapy" has become a rather 

 standardized procedure. 



