INTESTINAL SYNTHESIS 



who found that the faecal excretion of riboflavine was 37 to 3-8 times 

 as great on a natural as on a synthetic diet, and actually exceeded the 

 dietary intake in many instances. 



Slightly different results were obtained by Denko ct al.}'^ to whose 

 work reference has already been made (see page 77). They found 

 that the combined faecal and urinary excretion of riboflavine by seven 

 healthy young men on a normal diet was just about equal to the 

 dietary intake of riboflavine ; the amount excreted in the faeces 

 (1-03 mg. per day) was nearly twice that excreted in the urine (o-68 

 mg. per day). Moreover, the faecal excretion remained the same on 

 a vitamin-deficient diet and was unaffected by vitamin supplementa- 

 tion, whereas the urinary excretion of riboflavine dropped markedly 

 on a restricted diet, but returned to its original value on supplementa- 

 tion.^^ Similar results were obtained with infants.^'" Obviously these 

 experimental subjects behaved in a different manner from those of 

 Najjar et al., who appear to have obtained somewhat unusual con- 

 ditions. What the conditions are that will induce bacterial synthesis 

 of riboflavine in man and so prevent the appearance of deficiency 

 symptoms, are not yet known, but it is obviously of great scientific 

 interest to determine them. The application of such knowledge to 

 nutrition is also of considerable practical importance, since it provides 

 a possible alternative to treatment of riboflavine deficiency by admin- 

 istration of pure riboflavine or of concentrates. 



Riboflavine, like aneurine, is synthesised 1* by the intestinal 

 organisms. Bacillus proteus vulgaris, B. lactis aerogenes, B. mesentericus , 

 B. vulgatus, B. faecalis alcaligenes and Escherichia coli. 



Synthesis of Riboflavine in Ruminants 



A general outline of the work leading to the recognition that " vita- 

 min B " was synthesised by the bacterial flora of the rumen of cattle 

 and other ruminants has already been given (see page 79). Evidence 

 for the synthesis of riboflavine was presented by L. W. McElroy and 

 H. Goss,^^ who found that the rum.en of sheep receiving a ration con- 

 taining less than 0-3 /xg. of riboflavine per g. contained 33 /xg. per g., 

 whilst the rumen of cows fed a simijar ration contained 25 /cxg. of ribo- 

 flavine per g. The milk from these cows, after removal of the cream, 

 contained 20 /xg. of riboflavine per g. Whereas the dietary intake was 

 1-8 mg. per day, the amount secreted in the milk alone was 16 to 18 

 mg. per day. Thus bacterial synthesis may largely be responsible 

 for one of the main sources — milk — of riboflavine in the human dietary. 

 These results were confirmed by Hunt et al.}^ who showed that bac- 

 terial synthesis in the rumen of cattle was enhanced when the diet 

 contained a large proportion of carbohydrate. On a ration of maize, 



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