230 



VITAMINS 



tensity of this fluorescence serves as a measure of the amount of thiamine 

 that was present in the food. Such assay methods are now used much 

 more extensively than the longer animal feeding methods, although the 

 latter are still relied upon as the final test. 



Courtesy of ]\Iei'<'k & Co., Inc. 



Fig. 9-6. Thiamine. 



Occurrence 



The richest known source of thiamine is brewer's yeast. It has been 

 found, however, by Kingsley and Parsons that the greater part of the 

 thiamine (and riboflavin) in yeast is not utilized by human beings unless 

 the yeast is given some previous treatment such as cooking which kills 

 the yeast cells. Next in order of concentration follow pork muscle, rice 

 polishings, and bran of grains. Obviously, cereals can constitute a good 

 source of this vitamin only when the entire grain is used. If considered 

 on the dry basis, most vegetables and fresh fruits are fairly potent 

 sources. Eggs and most meats contain appreciable amounts of the vita- 

 min. Synthetic thiamine is being employed to an increasing extent for 

 the fortification of commercial foods, particularly white flour. 



Requirements 



The amount of thiamine needed daily by a normal person depends on 

 the amount and kind of food that he consumes. As indicated above, 

 this vitamin functions in the metabolism of carbohydrate in the body, 



