400 RIBOFLAVIN 



in amounts which are far in excess of the daily requirement. Without these 

 classifications the researcher in nutrition would not know what to look for. 



Excellent examples of the population survey type of study have been 

 described by Goldsmith^^ and by Wilkins and Sebrell.'*^ Wilder^" has sum- 

 marized the extensive surveys of malnutrition in Newfoundland^^"^^ to 

 show how the enrichment of flour benefited the population. But, although 

 these surveys were of great value to our understanding of the nutrition of 

 population groups, they are difficult to interpret in terms of the require- 

 ment of the individual. 



The experimental production of riboflavin deficiency has been successful 

 only in those studies in which levels of 0.55 mg. of riboflavin per day or 

 less have been fed. Those investigators who provided 0.8 mg. per day to 

 their subjects could not produce signs of ariboflavinosis. Nevertheless, no 

 nutritional authority has yet suggested that 0.8 mg. is adequate for optimal 

 health. Rather, one recommends amounts which provide somewhat more 

 than the minimal daily need as fortification against unknown contingen- 

 cies. The concept that riboflavin cannot be stored may not be entirely 

 correct, since even at dietary levels of 0.5 mg. per day about 6 months 

 must elapse before signs of ariboflavinosis appear. 



One of the more important advantages of depletion studies is the oppor- 

 tunity provided for simultaneous investigation of urinary excretion. Since 

 the urinary excretion is a reflection of the dietary intake and the dietary 

 intake is, in the last analysis, the cause of riboflavin deficiency, it is under- 

 standable why so much effort has been devoted to the study of riboflavin 

 in urine. 



Load tests, in which a known amount of riboflavin is administered and 

 the percentage excreted is determined, are useful means of estimating the 

 degree of saturation of the tissues. Although the usual procedure is to ad- 

 minister riboflavin in the post-absorptive state and to analyze the riboflavin 

 excreted during the following 4 hours, a 24-hour collection may be consid- 

 ered a load test if the dietary intake during that period is known. Gold- 

 smith^* has reviewed the literature on the use of urinary excretion tests in 



« G. A. Goldsmith, Federation Proc. 4, 263 (1945). 



49 W. Wilkins and W. H. Sebrell, Federation Proc. 4, 258 (1945). 



50 R. M. Wilder, Federation Proc. 9, 562 (1950). 



" G. A. Goldsmith, W. J. Darby, R. C. Steinkemp, A. S. Beam, and E. McDevitt, 



J. Nutrition iO, 41 (1950). 

 52 J. D. Adamson, N. Jolliffe, H. D. Kruse, O. H. Lowry, P. E. Moore, B. S. Piatt , 



W. H. Sebrell, J. W. Tice, F. F. Tisdall, B. M. Wilder, and P. C. Zamecnik, Can. 



Med. Assoc. J. 52, 227 (1945). 

 " W. R. Aykroyd, N. Jolliffe, O. H. Lowry, P. E. Moore, W. H. Sebrell, R. E. Shank, 



F. F. Tisdall, R. M. Wilder, and P. C. Zamecnik, Can. Med. Assoc. J. 60, 329 



(1949). 

 " G. A. Goldsmith, Federation Proc. 8, 553 (1949). 



