STUDIES ON FATS, OILS, AND FATTY ACIDS 221 



digestibility was 97.0; these tests included the soap fraction. Severance 41 

 also reported a correspondingly high figure (95.2) for the digestibility of 

 margarine in rats when the total fecal lipids were determined by a variety 

 of procedures. Finally, Calbert et at. 1 reported a number of series of 

 tests on rats with margarine fat alone at a level of 15, 22.5, or 25% of the 

 diet; the digestibility of the margarines in all cases exceeded 95%. Cor- 

 responding figures indicating a high digestibility were likewise noted in 

 tests in which isopropyl citrate was also present in the diet. The di- 

 gestibility was somewhat depressed in rat tests when stearyl citrate was 

 included in the diet at high levels; this effect, however, was not observed 

 in dogs, and is believed to be the result of an abnormal condition produced 

 by the inclusion of excessive quantities of a high-melting wax. Calbert 

 and associates 7 were likewise able to prove the high digestibility of mar- 

 garine fat in dogs (99.2 to 100%) when the fecal soaps were included in 

 the calculations. 



The complete utilization of the modern margarines would be expected 

 because of the additives included in these preparations. Thus, it is 

 believed that the absorption is facilitated by the presence of monoglyc- 

 erides, diglycerides, and lecithins contained by practically all margarines. 

 In fact, it has been reported 69 that margarine is also an excellent vehicle 

 for the feeding of /3-carotene, since a higher provitamin A potency was 

 found than might be expected if the carotenoid were administered in a fat 

 devoid of the additives. This augmentation in effect is believed to be 

 related to a more satisfactory absorption of the carotenoid when ad- 

 ministered in margarine. 



{2) Studies on Animals Other Than Man 



a. Digestibility of Natural Fats. There is general agreement that, in 

 most cases, the pattern of digestibility of fats is similar in man, dog, and 

 the rat. On the other hand, McCay and Paul 70 reported that guinea pigs 

 digest some of the high-melting vegetable and animal fats poorly. Cook 71 

 and also Cook and Thomson 72 have confirmed the low digestibility of 

 several fats in guinea pigs. On the other hand, rabbits and sheep were 

 shown by Paul and McCay 73 to have higher coefficients of digestibility for 



69 H. J. Deuel, Jr., S. M. Greenberg, E. E. Savage, and D. Melnick, J. Nutrition, 

 48, 371-387 (1951). 



70 C. M. McCay and H. Paul, ./. Nutrition, 15, 377-382 (1938). 



71 It. P. Cook, Biochem. J., 51, xiii (1952). 



72 R. P.. Cook and R. O. Thomson, Quart. J. Exptl. Physiol, 36, 61-74 (1951). 



73 H. Paul and C. M. McCay, Arch. Biochem., 1, 247-253 (1942). 



