834 XIII. ESSENTIAL FATTY ACIDS 



ous blood vessels. The EFA are required for successful pregnancy and 

 lactation. It has recently been shown that the essential fatty acids are 

 necessary for normal cholesterol transport and metabolism in the rat. 

 In the absence of fats from the diet, the cholesterol content in the liver and 

 adrenal tissue reaches abnormally high values ; it promptly returns to nor- 

 mal when fats containing the EFA, or the EFA themselves, are added to 

 the diet. The requirement for EFA in the rat has been shown to be a sex 

 function; apparently much larger amounts are required for optimum 

 growth by the male than by the female rat. One interesting recent report, 

 which has not as yet been confirmed, is the finding that 7-linolenic acid, 

 6,9,12-octadecatrienoic acid, is the active isomer of linolenic acid in causing 

 growth, rather than ordinary linolenic acid, 9,12,15-octadecatrienoic acid, 

 as was formerly believed. 



