THE FOOD OF MANKIND 



coefficients of absorbability of the several constituents of the 

 different foodstuffs. A great part of our knowledge on this 

 subject is due to the admirable work done in the different nutrition 

 laboratories in America in connection with the U.S. Department 

 of Agriculture. Hutchison * summarizes the results in the table 

 on p. 34, constructed from the figures of Rubner and Atwater. 



From a large number of experiments on man, Langworthy f 

 calculates that on an average the different groups into which 

 foods may for convenience be divided have the following co- 

 efficients of digestibility : 



COEFFICIENTS OF DIGESTIBILITY OF DIFFERENT GROUPS PERCENTAGES. 



These figures show that the protein and fat of animal foods 

 are much more completely absorbed than those of vegetables, 

 with which there may be a loss in the faeces up to over 30 per cent, 

 of the total protein consumed. 



On the whole, however, it may be accepted that the foodstuffs 

 in use in Europe and America show a high percentage of absorp- 

 tion for the several proximate principles. Animal protein is 

 readily and completely digested, that of vegetables less com- 

 pletely. Fats are well digested, and carbohydrates show a high 

 coefficient of absorbability, except when the amount of crude 

 fibre or cellulose is large. 



On a fruitarian diet the digestibility is not quite so good. 



Jaffa gives the following results based on thirty digestion 

 experiments with fruit dietaries : 



Protein 



Fat .. 

 Sugar. . 

 Fibre 

 Calories 



75 per cent, absorbed. 



86 



95 



79 



86 



* Hutchison, " Food and the Principles of Dietetics," 1911. 



f Langworthy, Circular No. 46, U.S. Department of Agriculture. 



