238 III. DIGESTIBILITY OF FATS 



extent of digestibility of most fats was markedly reduced when these salts 

 were included in the ration. The data from these tests are summarized in 

 Table 18 (p. 236). 



The digestibility of a hydrogenated lard melting at 55°C. was reduced 

 from 78 to 58% in the presence of calcium. Trimyristin was found to be 

 digested to the extent of 77% in the absence of calcium and of only 36% 

 when calcium salts were present. It was also reported that the depressing 

 effect of calcium salts was in proportion to the quantity present. Thus, 

 trilaurin had the following coefficients of digestibility, respectively, in diets 

 containing 6.1, 2.5, 1.17, and mg. of calcium per gram of food: 70.5, 

 87.2, 89.5, and 97.3. 



Givens 112 was among the first to report that the excretion of fecal cal- 

 cium was increased when the absorption of fat was poor. In fact, this 

 worker reported that calcium storage was decreased under such condi- 

 tions, even when the calcium intake was at a high level. The extent of 

 soap formation was believed by Bosworth and co-workers 113 to be a func- 

 tion of the ionized calcium present, although the amount excreted in the 

 feces depended upon the proportion of the soaps which were soluble. 

 Since calcium oleate is more readily soluble in bile than calcium palmitate 

 or calcium stearate, it will disappear in larger quantities than the two 

 latter salts, even in the presence of an excess of calcium. Similar data 

 are recorded by Boyd and collaborators. 114 They found that, when rats 

 had a calcium intake of 37 to 56 mg./day, the utilization of oleate, palmi- 

 tate, and stearate soaps was 90, 38, and 25%, respectively. On the other 

 hand, when the intake of calcium was lower (20 to 32.5 mg./day), the 

 digestibilities of palmitate and stearate were increased to 65 and 45%, 

 respectively, while the figure for calcium oleate was 91%. Confirmation 

 of the depressing effect of calcium on the utilization of fats containing 

 saturated fatty acids was given by Rao and De. 114a When coconut oil 

 was fed to rats, no appreciable change in the digestibility coefficient of 

 98.4 was noted, irrespective of whether or not calcium salts were present 

 in the diet. Furthermore, the coefficient of digestibility in the unsaturated 

 fraction of coconut oil was not altered when calcium was present. How- 

 ever, it was shown that the coefficient of digestibility of the saturated frac- 

 tion (m.p. 52°C.) was decreased from 89.1 to 80.0 when the diets con- 

 tained calcium. 



112 M. H. Givens, J. Biol. Chem., 31, 441-444 (1917). 



113 A. W. Bosworth, H. I. Bowditch, and L. A. Giblin, Am. J. Diseases Children, 15, 

 397-407 (1918). 



114 O. F. Boyd, C. L. Crum, and J. F. Lyman, J. Biol. Chem., 95, 29-41 (1932). 

 114a M N Rao and g g De , Indian J. Med. Research, 89, 457-464 (1951). 



