300 



ESSENTIAL FATTY ACIDS 



a fatty infiltration of the liver (Fig. 11) which is prevented by fat in the 

 diet.^ In this respect, essential fatty acids are lipotropic. 



The best histological studies on the skin lesions of fat deficiency have 

 been made on the dog.^"* The abnormalities include loss of hair and des- 

 quamation, and compactness of the stratum corneum. The epidermis 

 thickens and there is edema in the dermis. Hair follicles become hyper kera- 

 tinized, the hair shafts become plugged, and the sebaceous glands enlarge. 

 Illustrations of the epidermis of dogs on low fat and normal diets are shown 

 in Fig. 12. 



The pathological conditions recognized as essential fatty acid deficiency 

 are generally produced by maintaining animals on a low -fat or fat-free diet. 

 Such diets are used because it is difficult to prepare a diet free of essential 



Fig. 12. Epidermis of dogs (a) on control diet and (b) on low-fat diet. 120X. (From 

 Hansen et al.^*) 



fatty acids without removing all fat. These diets supplemented with 

 essential fatty acids in adequate amounts still do not allow optimum growth, 

 reproduction, and lactation, but the pathological states developed on such 

 a dietary regime are still poorly characterized. The studies of pathology of 

 fat-deficient animals have not differentiated between the two types of fat 

 deficiency, but the pathological changes described are prevented or cured by 

 linoleate, thus making it reasonably certain that the conditions described 

 are due to essential fatty acid deficiency. 



B. IN HUMAN BEINGS 

 ARILD E. HANSEN and HILDA F. WIESE 



Specific information regarding the essentiality of linoleic acid and arachi- 

 donic acid in relation to human nutrition is completely lacking. Hence, in 

 a discussion of the human requirement for these fatty acids, it is necessary 



