Chapter IA 



B VITAMINS: WHAT THEY ARE 



Historically the term "vitamin B" was applied to the water-soluble 

 organic material present in yeast, wheat germ, protein-free milk, etc., 

 which was found to be necessary in small amounts for the nutrition of 

 young animals. At the time this designation came into general use the 

 dietary importance of minerals, proteins (amino acids), carbohydrates, 

 fats, "vitamin A," and vitamin C was recognized, and "vitamin B" meant 

 something distinct from these other recognized food materials. 



When it became evident that vitamin B was not a single substance but 

 several, the designations Bi, B 2 , B 3 , etc., were introduced. These have 

 more recently given way in most cases to names for the specific chemical 

 substances involved: thiamine, riboflavin, etc. We shall discuss later 

 specific cases of substances which according to one's point of view may 

 or may not be included among the "B vitamins." 



The time may well arrive when the term "B vitamin" will be abandoned, 

 and each specific chemical substance will be considered entirely as a 

 separate entity. At the present time, however, there is good reason for 

 retaining the term, because B vitamins appear to have common attributes 

 which set them apart from all other vitamins. 



Microbiological assay methods have made it possible to learn that the 

 specific compounds commonly considered as members of the B family 

 are universally distributed in all living cells, whether of plant, animal or 

 bacterial origin. Since this appears not to be true of any of the other 

 vitamins, it was suggested elsewhere that B vitamins may be tentatively 

 defined as those which occur as indispensable constituents of all living 

 matter. 1 If this suggestion is valid, their fundamental importance is self- 

 evident. 



Studies relating to the functioning of individual members of the B 

 family of vitamins have demonstrated that they are integral parts of 

 biological catalytic systems and that they constitute essential factors 

 in the metabolic machinery of widely diverse forms. It seems probable 

 that this is true of all of the B vitamins, and an amended definition may 

 include this idea. In this case, we may say that B vitamins are those 

 which enter into the catalytic systems of all living cells. 



Since the water solubility or fat solubility of a compound is not absolute 



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