METABOLISM OF THE B VITAMINS 339 



B vitamins may occur. These effects may be produced as the result of 

 enzymes indigenous to the animal, or as the result of intestinal microflora; 

 but in most cases it is not now possible to distinguish whether one or 

 both factors are involved. The establishment of whether the digestive 

 effect is due to animal or microfloral action is important, since the assess- 

 ment of factors which may affect the digestive process must be made in 

 terms of which member of this digestive partnership is involved. When 

 large amounts of a nutritional component are processed in the digestive 

 tract, bacterial effects upon the component may be negligible; but in the 

 case of small amounts of catalytic materials, bacteria may move the 

 digestive process into a radically different channel. 



The part of the B vitamin nutritional intake which is supplied by 

 bacteria is (most logically) largely present in the intestine in free form, 

 and is not further materially affected by the digestion. A large fraction 

 of the exogenous B vitamin nutrition is in bound form, however. In some 

 cases cooking of the food may suffice to break the complex. This is reported 

 to be markedly true in the case of riboflavin, and to a variable and lesser 

 extent in the case of the other vitamins; it is, of course, dependent upon 

 the conditions of temperature, pH, and concentrations of other ingredients. 

 Cooking does not produce sufficient liberation of available forms to be 

 considered as a major factor in the process. While some liberation may 

 occur in the stored uncooked food as the result of ripening processes or 

 autolysis, this factor seems not to be of any considerable importance in 

 the overall liberation. Thus, water-soluble choline compounds (choline 

 glycerophosphoric esters) appear quite rapidly when rat intestine and 

 stomach are allowed to autolyze, but there is only very slow liberation 

 in lung and kidney autolysates, and scarcely any in brain, liver, and 

 heart. 7 



The B vitamin-protein complexes of the food are to a great extent 

 broken down in the gastrointestinal tract, and a limited amount of 

 evidence suggests that this process occurs largely in the duodenum. This 

 process may not be as efficient in some cases as in others, and in the case 

 of pantothenic acid complexes particularly, there is some evidence to 

 suggest that the liberation is not as complete as in the case of the other 

 B vitamins. 8 Since it seems quite likely that the functional form of 

 pantothenic acid, unlike most of the other B vitamins, involves a union 

 of the vitamin with an amino acid (glutamic acid), it seems pertinent 

 to suggest that the binding of pantothenic acid may be stronger for this 

 reason. Similarly the apparent unavailability of some of the more complex 

 forms of folic acid to some bacteria and to pernicious anemia patients 

 suggests that a vitamin connected in its functional form (coenzyme) to 



