920 XIV. NUTRITIOXAL VALUE OF FATS 



starch, dextrin, dextrimaltose, or lactose, and moderate amounts of thi- 

 amine, ril)oflavin, pyridoxine, pantothenic acid, and chohne, the rats which 

 received butterfat grew at a faster rate than did those fed corn oil. This 

 inferiority of corn oil could be minimized in the group on lactose rations, 

 and was eliminated in those on all other rations, by raising the level of 

 these vitamins, and by adding high levels of inositol, p-aminobenzoic acid 

 and nicotinic acid, plus 1% of whole liver powder. No differences in 

 growth were noted at any vitamin level when glucose or galactose-glucose 

 mixtures were the rations emploj^ed in the tests. On the basis of these 

 experiments it has been assumed that butterfat stimulates the synthesis of 

 the vitamins B in the intestinal tract more than is the case with corn oil. 

 However, in view of the rather small differences in body weight noted when 

 butterfat or the corn oil, respectively, Avas employed, these experimental 

 data do not seem to be of much practical importance in assessing the com- 

 parative nutritional value of the two types of fat. 



One criterion employed in evaluating the nutritional efficiency of butter- 

 fat as compared with corn oil is the level at which it is fed in the diet. Thus, 

 when high levels of the fat were given (35%) the rats recei\'ing the butterfat 

 diets gained the most weight while, in the groups maintained on lower levels 

 of fat (10%), those receiving the corn oil did better, insofar as gain-in- 

 weight was concerned. '" On the other hand , changes in the level of coconut 

 oil or of soybean oil in the diet did not result in significant changes in 

 growth. It is thus suggested that the different fats produce optimum 

 groAAi^h at different levels of intake, so that this fact must be taken into 

 consideration in the comparative evaluation of their nutritive values. *^^ 



(3) The Effect of Heating upon the Nutritional Value of Fats and Oils 



The effect of polymerization was discussed in Vol II of The Lipids, pp. 

 232 ff. 



It has been suggested that the heated fats may develop some carcinogenic 

 activity. Dunning et aU°^ reported that a diet high in fat shortened the 

 latent period and increased the number of malignant mammary tumors 

 induced by diethylstilbestrol in rats. The effect of the high-fat diet could 

 be inhibited by caloiic restriction. Lane, Blickenstaff, and Ivy*^^ reported 

 a greater incidence of cancerous stomach lesions when "browned" lard which 

 had ))een heated at 3r)0°C. for thirty miimtes was fed to rats, than when 



«^ V. H. Barki, R. A. Collins, C. A. Elvehjem, and E. B. Hart, ./. Nutrition, 40, 38:i- 

 392(1950). 



«8 W. F. Dunning, M. R. Curtis, and M. E. Maun, Cancer Research, 9, 354-3GI (1949). 

 «' A. Lane, D. Blickenstaff, and A. C. Ivy, Cancer, 3, 1044-1051(1950). 



