FACTORS AFFECTING THE REqUIREMENT 805 



the levels in male rats. For a further discussion of these and other aspects 

 of sex difference in fat metabolism, the reader is referred to other publica- 

 tions of Deuel. ^'-^^^^ 



It is not surprising therefore to note that the optimum requirement for 

 linoleate varies with sex. Data on the requirement of EFA for growth are 

 available only for the rat. If one accepts maximum gain-in-weight during 

 the assay period as an index of optimum nutrition, then one must conclude 

 that the daily requirement for male rats probably exceeds 200 mg. This 

 conclusion was reached on the basis that the curve obtained, when the gain- 

 in-weight is plotted against log dose, is a straight line not only for several 

 daily dosages up to 100 mg. as observed by Greenberg et al.,^^'^'^ but even 

 for 200 mg., according to Deuel, Greenberg, Anisfeld, and Melnick.'^^ 



In contradistinction to these results, on the basis of similar experimental 

 data, the daily requirement of the female rat for EFA does not exceed 100 

 mg. and probably varies between 20 and 50 mg., as stated by Greenberg 

 et al.^^ and by Anisfeld et al.^^^ Anisfeld and her co-workers^^^ likewise 

 reported that the reduced growth response of the female rat to increasing 

 doses of linoleate is not related to variations in the tocopherol requirement 

 of the sexes. Cheng, Kryder et a/.^^" also noted that sex plays a role in the 

 protective effect of fats against x-irradiation injury. Thus, the male can 

 be protected b}^ fats from x-irradiation under conditions which afford no 

 protection for the female. Although all of the data concerning sex differ- 

 ences in requirement for EFA have been obtained on the rat, there is no 

 reason to believe that the sex factor is unique for this species. One must 

 come to this conclusion if one accepts the fact that this is only one of the 

 expressions of sex variation in fat metabolism, a phenomenon which has 

 been shown to be shared by many species, including man. 



(3) The Effect of Substances Fed Concomitantly 



a. Fatty Acids. The fat-deficiency syndrome has been found to develop 

 much more rapidly when saturated fatty acids are fed to the rat along with 

 the EFA-deficient diet. Evans and Lepkovsky^" reported, as early as 

 1932, that the fat-deficiency syndrome developed more rapidly in rats on an 

 EFA-free diet than in anunals on a similar diet devoid of the saturated fat. 

 These findings were confirmed by Sinclair^^' and by Deuel et al?^ In a later 



"^ H. J. Deuel, .Jr., The Wholesonieness and Nutritional Value of Fats and Oils, Speciul 

 brochure pre])ai'e(l loi- the Institute of Shortening and Edible Oils, Inc., 1954. 



139 L. Anisleld, S. M. Greenberg, and II. J. Diniel, Jr., ./. N idrition, 45, 599-G07 (1951). 



I'W A. L. S. Cheng, G. 1). Kryder, L. Bei-gquist, and H. J. Deuel, Jr., ./. N idrition, 48, 

 lGl-182 (1952). 



1" R. O. Sinclair, /. Biol. Chem., 114, xciv (193G). 



