OPrntUM LEVELS OF FAT 931 



to that of the hydrogenated lard itself. The absorption of the digestive 

 pi'oducts of the distilled acetjdated monoglyoerides depended largely upon 

 their fatty acid composition.'"'^'^"* 



Alexander and Mattson^'^ fed a vitamin A supplement to a control group 

 of vitamin A-depleted weanling male rats maintained on a diet containing 

 14% fat in the form of a mixture of hydrogenated soybean and cottonseed 

 oil, and to a similar group gi^'en a mixture of monoacetin and diacetin 

 derived from the control fat. The acetin fat facilitated the absorption of 

 the vitamin A, and promoted its storage in the liver, at least as efficiently 

 as did the control fat. A normal rate of utilization of vitamin A from the 

 liver was noted in the case of the rats fed acetin fats. 



Herting'*-" found that feeding acetj'lated monogh'cerides to rats at dietaiy 

 levels up to 50% increased the lipid-bound, steam-distillable acids in the 

 blood, but not in the carcass fat. The low level of these acids found in the 

 tissue fat of a dog fed standard dog-meal was not increased by feeding a 

 diet containing 25% of acetj^lated monoglycerides. Samples of human 

 blood lipids contained relatively large amounts of the acids. 



5. Optimum Levels of Fat in the Diet 



(1) Conclusions Based upon Experiments on Rats 



The beneficial effects of fat in the diet are so varied in character as to 

 raise the question whether fats are only optional components of the diet or 

 whether they should be regarded as necessarj' foodstuffs. The figure at 

 which the optimum level is established depends to some extent upon the 

 method of evaluation. Results of the methods which have been employed 

 on rats, as described in the earlier portion of this chapter, indicated that 

 the best performance was obtained when the diet contained 20 to 40% of 

 fat by weight. There are, however, some instances in which quite satis- 

 factory results were obtained when onlj^ 10% of the diet consisted of fat. 

 One factor Avhich certainly plays a role in determining the amount of fat 

 needed in the diet is the tj^pe of fat employed. Thus, fats which are com- 

 pletely saturated or which contain none of the EFA probably would not 

 result in optimum performance even if fed in large quantities. The amount 

 of fat needed to supply the EFA varies according to the particular situation 



^18 S. R. Ames, D. C. Herting, M. Koukides, and P. L. Harris, Federation Proc, 14, 173 

 (1955). 



*i9 J. C. Alexander and F. H. Mattson, Federation Proc, 15, 541-542 (1956). 



*^ D. C. Herting, S. R. Ames, X. D. Embree, and P. L. Harris, Federation Proc, 15, 

 556(1956). 



