CHAPTER X 



THE METABOLISM AND NUTRITIONAL 

 VALUE OF THE VITAMINS D 



Although the physiologic role of the fat-soluble vitamins other than 

 vitamin A is not so well understood as is that of the latter vitamin, recent 

 discoveries have indicated that each fat-soluble vitamin mediates important 

 specific independent physiologic changes. The following three chapters 

 will briefly review the background material presented earlier in Volumes I 

 and II of The Lipids concerning each of the three fat-soluble vitamins, D, 

 E, and K. This will be followed in each case by a discussion of the meta- 

 boHc aspects and the physiologic roles played by each vitamin. 



1. Introduction 



(-?) Rickets 



As in the case of vitamin A, vitamin D was discovered because of the 

 therapeutic effect of preparations in which it was present on the avitamino- 

 sis occurring when this vitamin was absent from the diet of animals and of 

 humans. The deficiency disease arising in animals and in children lacking 

 \'itamin D is referred to as rickets. According to Nicolaysen and Eeg- 

 Larsen/ the terminology for this condition originated from the verb in the 

 local Dorsetshire dialect, "to rucket," which meant "to breathe with dif- 

 ficulty." Bills, 2 writing in Sebrell-Harris The Vitamins, attributed the 

 origin of the term, rickets, to the word, wry gates, which in turn means 

 "crooked goings." In contradistinction to the use of the terms, rickets, 

 ricketic, and antiricketic in the English literature, rachitis is the word em- 

 ployed by the Germans to describe this abnormality. The latter term is pre- 

 sumably derived from the Greek word, rachis, meaning spine. ^ The term 

 rachitis, and the related rachitic and antirachitic, have been widely em- 

 ployed in the American literature. The French have used a similar root in 



1 R. Nicolaysen and N. Eeg-Larsen, Vitamins and Hormones, 11, 29-60 (1953). 



2 C. E. Bills, in W. H. Sebrell, Jr., and R. S. Harris, The Vitamins, Vol. II, Academic 

 Press, New York, 1954, pp. 132-223. 



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