180 



II. DIGESTION AND ABSORPTION OF FATS 



come modified after longer periods. The author has found that much 

 smaller variations are to be observed in tests lasting for three or four hours. 



(2) The Nature of the Fat 



There is no doubt that the nature of the fat itself is of prime importance 

 in establishing the rate of absorption. If one subscribes to the Frazer 

 hypothesis of fat absorption, then variations in physical properties may well 

 be the factor responsible for differences in absorption rate. On the other 

 hand, if fats must be split, as Verzar assumes, the differences between 

 several fats may reflect variations in the rate of hydrolysis, as well as in the 

 rate of absorption of the resultant fatty acids. 



a. The Rate of Absorption of Synthetic Simple Triglycerides. Because 

 all natural fats contain a wide variety of fatty acids, and consist chiefly 

 of mixed rather than of simple triglycerides, information concerning the 

 effect of the length of the fatty acid chain can more readily be obtained with 

 simple triglycerides than with natural fats. These data, however, can be 

 obtained only for the triglycerides with fatty acids lower than C12, since 

 the high melting point of the longer-chained compounds practically pre- 

 cludes their administration. Moreover, such high-melting fats are di- 

 gested and absorbed only to a minor extent. 



Table 25 



Summary of Results on Absorption of Synthetic Simple Triglycerides in Fasting 



Male Rats over Three-Hour Periods 



Even-chain fats 



Odd-chain fats 



Fat fed 



Number 



of 

 carbons 



Absorption. 



mg./lOO 

 sq. cm./hr. & 



Number Absorption, 



of mg./lOO 



Fat fed carbons sq. cm./hr. & 



Triacetin 



Tributyrin . . . 



Triisovalerin . . 



Tricaproin . . . 



Tricaprylin. . . 

 Tricaprin .... 

 Trilaurin 



2 68.1 ± 1.4(12) 



4. ...65.0 ± 2.5(10) 

 4. ...69.1 ± 2 . 7 ( 1 1 ) c 

 5... .45.7 =b 2.5(6) 



6.... 54. 5 



1.5(9) 



Tripropionin. . . .3. . . .31 .4 ± 2. 1 (12) 



Trivalerin 5. . . .32.9 ± 2.3(9) 



Triheptylin 7. . . .28.0 =fc 1.6(10) 



8. ...45.9 =fc 4.1(8) 

 10... d 



12... 21.9(5) 



• H. J. Deuel, Jr. and L. Hallman, J. Nutrition, 20, 227-232 (1940). 



b Including Standard Error of Mean. Figures in parentheses indicate the number of 

 tests included in average. 



c L. Bavetta and H. J. Deuel, Jr., Am. J. Physiol., 136, 712-715 (1942). Female rats 

 were used in these tests. 



d Diarrhea in all 20 tests. 



