NOEMAL FACTORS ALTERING DIGESTIBILITY OF FATS 239 



Conversely, the amount and nature of the dietary fat is of considerable 

 importance in relation to calcium retention. It is obvious that the cal- 

 cium loss will be minimal when the fatty acids in the dietary fat consist of 

 oleic acid and of other low-melting acids. However, when the melting 

 point of the ingested fat exceeds 50°C, marked loss of calcium in the feces 

 may be expected, and the loss will be proportional to the amount of fat fed. 



b. The Effect of Protein. A second dietary constituent, which may 

 modify the coefficient of digestibility of fat, is protein. It was first pointed 

 out by Barnes, Primrose, and Burr 115 that fats are digested to a lesser ex- 

 tent on a low-protein diet (14%) than on a dietary regimen having a 

 higher protein content (30%). These results have been confirmed by 

 Savage 116 and by Severance. 41 Munk 117,118 and Rosenheim 119 - 120 reported 

 that, when dogs were fed a low-protein diet for six to eight weeks, a serious 

 derangement in fat absorption occurred, which was apparently associated 

 with severe lesions in the gastrointestinal tract. The findings of Barnes 

 et al. nb and of Severance 41 are shown in Table 19, p. 237. 



On the other hand, Jagerroos 121 and Chittenden 122 were unable to find 

 any indication of a decreased capacity to digest fat in the case of dogs or 

 of human subjects maintained on a low-protein diet. Coffey el al. 123 

 likewise reported that the protein level has little effect on fat digestibility. 



c. The Effect of Crude Fiber. Walker 124 has observed that, on diets 

 with the same fat content, the amount of fecal fat was detectably increased 

 when the crude fiber in the diet was augmented. It is suggested that this 

 fecal fat is not of dietary origin, but that it may be derived from intestinal 

 secretions, from fatty acids produced by bacterial action on cellulose, or by 

 bacterial synthesis. Walker believes that the wide differences in the excre- 

 tion of fecal fat by different human subjects on a standard diet may be due 

 to the variations in the non-dietary fat excreted as a result of the ingestion 



116 R. H. Barnes, M. F. Primrose, and G. O. Burr, J. Nutrition, 27, 179-184 (1944). 

 116 E. S. Savage, A Comparative Study of the Utilization of Jojoba and Cottonseed Oil 

 in the Rat, Thesis, Univ. So. California, Los Angeles, Dept. Biochem. Nutrit., 1951. 

 117 1. Munk, Arch. Path. Anat. Physiol. (Virchow's), 132, 91-157 (1893). 

 118 1. Munk, Arch. Anat. u. Physiol, Physiol. Abt. (Du Bois-Reymond), 1891, 338-341. 



119 T. Rosenheim, Arch. ges. Physiol. (Pfluger's), 46, 422-432 (1890); 54, 61-71 (1893). 



120 T. Rosenheim, Arch. Anat. u. Physiol, Physiol. Abt. (Du Bois-Reymond), 1891, 

 341-344. 



121 B. H. Jagerroos, Skand. Arch. Physiol, 18, 375-418 (1902). 



122 R. H. Chittenden, Physiological Economy in Nutrition, Stokes, New York, 1905, 

 pp. 9, 10. 



123 R. J. Coffey, F. C. Mann, and J. L. Bollman, Am. J. Digestive Diseases, 7, 141-143 

 (1943). 



121 A. R. P. Walker, Nature, 164, 825-827 (1949). 



