FACTOKS ALTERING NUTHITIOIVAL VALUE 907 



importance in relation to the utilization of the fat studied. Absorption 

 denotes the rate at which fat is removed from the intestine into the body, 

 while digestibility is an index of the completeness of utilization as the food- 

 stuff passes through the gastrointestinal tract. Ordinarily fats which 

 have a high absorption rate also have a high digestibility. However, the 

 converse may not necessarily be true. 



Although no differences in nutritional value may be observed between 

 two fats which have the same coefficients of digestibility when the fats are 

 ingested in moderate quantities, variations in nutritional value may well 

 be noted if fats are taken in large amounts. Thus, a fat having a high rate 

 of absorption would still be completely utilized at a high level of intake; 

 on the other hand, a fat having a low rate of absorption may be only incom- 

 pletely absorbed, and may cause digestive disturbances, including diarrhea, 

 when taken in large amounts. The slowly-absorbed fat is definitely inferior 

 to the rapidly-absorbed one under such circumstances. If slowly-absorbed 

 and rapidly-absorbed fats are taken in small quantities, then the coefficient 

 of digestibility of the two fats would be the same, and they would provide 

 an equal number of calories. Absorption therefore provides an important 

 index as to the possible changes in nutritional value which are dependent 

 upon the size of the dosage. The subject of absorption of fats is discussed 

 in extenso in The Lipids, Vol. II, pages 115-134, while the rate of absorption 

 is discussed on pages 172-194. 



(a) Absorption Rates of Different Fats. The rate of absorption of various 

 fats and oils is generally highest when the concentration of the fats is at a 

 maximum. Thus, the figures in the test carried out at to three hours were 

 generally found to be somewhat higher than those for the second three- 

 hour period after feeding, although considerable amounts of fats still re- 

 mained in the gut at the end of a six-hour period. The variations in absorp- 

 tion rates of the different fats investigated are shown in The Lipids, Vol. 

 II, pages 176, 177. 



Although the number and variety of fats on which the rate of absorption 

 has been tested are exceedingly limited, certain variations appear to be 

 fairly regular. In the first place, the variations between natural animal 

 and vegetable fats are not great. The highest rate of absorption, in the 

 case of both males and females, seems to occur with butter. However, this 

 rapid absorption is noted only during the first three-hour period, and it 

 has largely disappeared by the second three-hour period. It is possible 

 that the more rapid absorption rate may be a reflection of the absorption of 

 the short-chain acids present in the butter triglycerides. The rate of 

 absorption of simple short-chain triglycerides is very rapid. Thus Deuel 



