218 III. DIGESTIBILITY OF FATS 



calculation of the coefficient of digestibility was based upon the fecal 

 lipid without soaps, as determined in the U.S.D.A. studies, the values 

 were actually somewhat lower than when the method of Folin and Went- 

 worth, 40 which includes soaps, was employed for the determination of 

 fecal lipids. In the tests of Deuel et al.* on cottonseed and rapeseed oils, 

 as shown in Table 9, the fecal fat was determined by a method which 

 included the soaps. The results of tests with these two oils by the two 

 analytical procedures were found to be identical. Moreover, the results 

 obtained on rats with a number of natural fats, 39,62 by analytical pro- 

 cedures which included the soap fraction, were substantially the same as 

 if the analysis had been made without acidification of the feces. The 

 failure to change the coefficient of digestibility when the fecal soaps were 

 included is explained by the fact that the increased lipid excreted as soap 

 was almost exactly counterbalanced by an increased metabolic "soap" 

 fraction. On the basis of these findings, it seems quite likely that the 

 U.S.D.A. results are substantially correct insofar as normal individuals 

 and fats with melting points below 50°C. are concerned. 



Somewhat lower results are reported by Holt el al. 63 for the digestibility 

 of coconut oil (88.7 and 89.8) in normal infants than are reported for 

 normal men; the latter averaged 97. 9. 64 On the other hand, Tidwell 

 and collaborators 65 observed that both olive oil and soybean oil were more 

 efficiently absorbed by premature infants than was butterfat. 



b. Digestibility of High-Melting Fats. It has long been recognized that 

 fats having melting points considerably above body temperature are less 

 completely digested than are those fats with lower melting points. Lang- 

 worthy and Holmes 2 stated, in 1915, that "it seems fair to conclude that 

 of those tested the fats of low melting points are capable of a more com- 

 plete assimilation than are those which have a high melting point." This 

 same opinion was expressed later by Holmes and Deuel, 66 who stated 

 that an inverse relationship obtains between the melting point and the 

 coefficient of digestibility. The results of experiments on animal fats 

 and on hydrogenated vegetable fats having high melting points are sum- 

 marized in Table 1 1 . 



The tests reported in Table 11 were carried out by employing methods 



62 M. E. Crockett and A. J. Deuel, Jr., J. Nutrition, S3, 187-194 (1947). 



63 L. E. Holt, H. C. Tidwell, C. M. Kirk, D. M. Cross, and S. Neale, J. Pediat., 6, 

 427-480 (1935). 



6 * C. F. Langworthy and A. D. Holmes, U. S. Dept. Agr., Bull. No. 505, 1-20 (1917). 

 " H. C. Tidwell, L. E. Holt, Jr., H. L. Farrow, and S. Neale, ./. Pediat., 6, 481-480 

 (1935). 



98 A. D. Holmes and H. J. Deuel, Jr., ./. Biol. Chew., >,1, 227-235 ( 1920). 



