STUDIES ON FATS, OILS, AND FATTY ACIDS 2 1 5 



carbon is tested. On the other hand, when the higher alcohol is fed as an 

 ester, the calculation becomes somewhat more involved. The estimation 

 of the digestibility of stearyl citrate and of the fat fed along with it is 

 summarized by Calbert and associates 7 as follows: 



D. Calculation of digestibility of total lipid by the usual methods 39 



E. Calculation of digestibility of fat alone 

 g. Determination of total fat fed 



h. Total fat excreted (corr.) = total fecal lipids — 



N.S.F. (corr 



:'] 



metabolic fat" - 



i. Digestibility of fat alone = (g - h)/g X 100 



F. Calculation of digestibility of wax 



j. Determination of total wax fed 



, _ , total N.S.F. excreted — control N.S.F. excreted 



k. Wax excreted = 



x 



1. Digestibility of wax = (j - k)/j X 100 



a Metabolic lipid is determined by total lipid excretion (neutral fat + soap) on fat- 

 free diet. 



6 Non-saponifiable fraction (corr.) = total fecal N.S.F. — N.S.F, of control groups. 

 c Factor for converting alcohol to ester (stearyl alcohol to stearyl citrate). 



3. Digestibility Studies on Fats, Oils, and Fatty Aeids 



(1) Studies on Human Subjects 



a. Digestibility of Vegetable and Animal Fats Melting Under 50° C. 

 In general, vegetable and animal fats which melt below 50°C. are almost 

 completely utilized by man. In most cases, the coefficients of digestibility 

 have been found to exceed 95. The chief exceptions to this rule are fats 

 which are irritating to the gastrointestinal tract, such as castor oil and 

 croton oil; these oils may fail to be appreciably utilized, while simultane- 

 ously preventing the efficient absorption of other foodstuffs. The most 

 complete study of digestibility of fats in man is undoubtedly that made 

 by the Office of Home Economics of the United States Department of 

 Agriculture, results of which have been summarized by Langworthy. 60 

 Data based upon the studies on vegetable fats are given in Table 9, while 

 those on animal fats are recorded in Table 10. 



The foregoing data indicate that vegetable and animal fats melting 

 under 50°C. are, in general, equally well digested and absorbed by normal 

 men when taken in amounts of 50 to 100 g. daily. Of the thirty-four 

 vegetable fats examined, all were digested to the extent of 94% or better, 



60 C. F. Langworthy, Ind. Eng. Chem., 15, 276-278 (1923). 



