FATS AS ESSENTIAL DIETARY COMPONENTS 885 



assume that any conditions which change the nutrient material available 

 to the intestinal flora will influence the amount of these vitamins which can 

 be utiHzed by the animal. Elvehjem'^^ reported that the rate of synthesis 

 is accelerated on a diet containing fat. Butterfat is believed to have a 

 greater effect than does corn oil in this synthesis. In addition to its sparing 

 action on thiamine and pyridoxine, fat exerts a similar action on niacin. 

 Salmon^^ reported that the requirement for nicotinic acid in the rat is 

 lower when fat is the chief source of calories than when the diet is pre- 

 dominantly carbohydrate. 



Biotin is also believed to exert a pronounced effect upon fat metabolism. 

 As early as 1927, Boas^^* observed that practically no body fat was present 

 in the tissues of rats which were subjected to severe biotin deficiency. 

 When this vitamin was administered to the rats, an increase in fat synthesis 

 occurred. 215 According to Pavcek and Shull,^^^ biotin is readily destroyed 

 by rancid fats, but tocopherol serves as an excellent agent in preventing 

 this destruction. 



Biotin also plays a major role in the growth of microorganisms, ^^^ whose 

 requirements vary according to the amount of oleic acid or of other un- 

 saturated acids present in the medium. 



Spivey and co-workers^^* reported that the addition of 20% of fat to a 

 vitamin Bi2-deficient diet in chickens increased the weight difference 

 between the chicks receiving the vitamin B12 and the unsupplemented 

 birds. Ling and Chow^'^ concluded that vitamin B12 plays an important 

 role in both carbohydrate and lipid metaboHsm. 



f. Fat-Soluble Vitamins. In some cases, the nature of dietary fat 

 markedly affects the requirement for the several fat-soluble vitamins. 

 Since some fats are excellent media for the solution and stabilization of the 

 fat-soluble vitamms, it is obvious that the quality and quantity of fat in 

 the diet are of prime importance in the absorption of these vitamins from 

 the gastrointestinal tract, and in their ultimate utilization. Muelder and 

 Kelly^^" reported that the absorption of vitamin A by depleted rats was 

 aided by dietary fat, although its subsequent utilization, as evidenced 

 by growth in body length, was independent of the level of this foodstuff 



"■* M. A. Boas, Biochem. J., 21, 712-724 (1927). 



218 G. Gavin and E. W. McHenry, /. Biol. Chem., I4I, 619-625 (1941). 



2'6 P. L. Pavcek and G. M. Shull, /. Biol. Chem., U6, 351-355 (1942). 



217 D. B. Melville, Vitamins and Hormones, 2, 29-69 (1944). 



218 M. R. Spivey, G. M. Briggs, and L. O. Ortiz, Proc. Soc. Exptl. Biol. Med., 85, 451- 

 453(1954). 



"3 C. T. Ling and B. F. Chow, /. Biol. Chem., 206, 797-805 (1954). 

 "« K. D. Muelder and E. Kelly, J. Nutrition, 23, 335-344 (1942). 



