INTESTINAL SYNTHESIS 



on the availability of biotin and folic acid either from the diet or from 

 the intestinal flora. 



Waisman et al}^ drew attention to the close similarity between 

 the symptoms of biotin deficiency caused by feeding e^g white and 

 those produced by the administration of succinylsulphathiazole, and 

 G. A. Emerson and E. Wurtz ^^ showed that the addition of succinyl- 

 sulphathiazole to a diet containing dried ^gg white did not modify the 

 severity or time of onset of biotin deficiency whether or not the diet 

 contained liver ; in order to secure growth, the diet had to contain 

 biotin plus liver or folic acid. It would seem from this evidence that 

 dried egg white makes unavailable not only dietary biotin but also 

 biotin derived from bacterial synthesis in the intestine. This was 

 confirmed by McGregor et al}^ who showed that biotin from a non- 

 dietary source was eliminated in the faeces of rats fed raw egg white, 

 the amount of biotin in the urine and faeces far exceeding that in the 

 diet. The excess biotin was presumably derived from the intestinal 

 bacteria and not from biotin reserves in the body. 



Proof that intestinal synthesis occurs in man was obtained from 

 metabolic experiments. Thus, T. W. Oppel ^* showed that, whereas 

 the urinary output of biotin was roughly proportional to the intake, 

 the daily faecal excretion greatly exceeded the intake. The total 

 excretion on a diet supplying 30 to 40 /xg. per day was in fact three to 

 six times this amount. Incidentally faeces, unlike urine, contained 

 no non-avidin combining fraction (page 433). These observations 

 were confirmed by Gardner et al}^ who found that in women, the total 

 biotin output was nine, three and 1-5 times the intake with diets 

 containing small, moderate and large amounts of biotin respectively. 



These results were also confirmed by Denko et al}^ (see page 377), 

 who in addition found that on a restricted diet a moderate decrease in 

 the urinary excretion of biotin occurred, the amount being roughly 

 equal to the dietary intake. The faecal excretion, on the other hand, 

 greatly exceeded the intake on the restricted diet. 



Several organisms are probably responsible for the intestinal 

 synthesis of biotin. Certainly B. proteus vulgaris can synthesise all 

 known members of the vitamin B complex,^'* -^^ whilst E. colt, B. lactis 

 aerogenes, B.faecalis alcaligenes, B. mesentericus and B. vulgatus produce, 

 inter alia, biotin.^® 



The effect of feeding various carbohydrates on the faecal flora and 

 so on the intestinal synthesis of biotin in the hen was studied by 

 Johansson et al}^ With sucrose as carbohydrate the faeces were 

 nearly devoid of coliform organisms, which were replaced by yeasts. 

 The coliform count was highest in hens receiving dextrin or a mixture 

 of sucrose and lactose. Intestinal synthesis of biotin occurred in hens 

 fed the basal ration with added dextrin, but not with sucrose or 



435 



