4 BULLETIN 469, U. S. DEPARTMENT OF AGRICULTURE. 



meat, which is the chief article of diet. Though it seems to be less 

 well known, it is nevertheless true, that fats are also eaten in consid- 

 erable quantity in tropical countries, as is evident when one recalls 

 the coconut oil of the South Sea Islands and the olive oil and other 

 fats so much used in cookery in other regions characterized by a very 

 warm climate. As everyone knows, dwellers in temperate regions use 

 fat in the diet in many ways, which are determined largely by the pre- 

 vailing food habits and the kinds of fat procurable, and in quantities 

 which bear a more or less direct relation to the amount of physical work 

 performed. Men engaged in severe work out-of-doors often eat large 

 quantities of fatty foods. Workmen in lumber camps, for instance, 

 relish a diet of pork and beans and other fat foods which would be 

 too hearty for the office worker or clerk. It is difficult to obtain any 

 definite figures for the quantity of fat eaten by the average person, 

 but in 1,300 dietary studies of families, carried out among different 

 races and in different countries, it was found that the average quan- 

 tity of fat eaten was about 4| ounces per person per day, the varia- 

 tion recorded being from \\ to 13 ounces per person per day. 



While fats and carbohydrates may replace each other to a consid- 

 erable extent, recent investigations indicate that some carbohydrate 

 supplied by the food or formed in the body from protein is essential 

 for the combustion of fats in the body. Experts in nutrition and 

 dietetics, therefore, believe that neither one should be used to the 

 exclusion of the other. 



DIGESTIBILITY OF FATS. 



While all fats yield approximately equal amounts of energy when 

 burned outside of the body, the energA^ which the body actually de- 

 rives from each is dependent upon its digestibility ; that is, the pro- 

 portion which the body retains. The digestibility of a number 

 of the individual fats x has been determined, and the information 

 at present available indicates that fats in general are very thoroughly 

 digested; more so, indeed, than the animal or vegetable proteins 

 and the starch occurring in the ordinary mixed diet. Such 

 slight differences as have been observed in the digestibility of in- 

 dividual fats evidently correspond to differences in their melting 

 points. Available evidence indicates that fats such as mutton fat, 

 having a melting point higher than the body temperature, are less 

 completely assimilated than those melting at a lower temperature, 

 such as lard, butter, olive oil, and cottonseed oil. Also, it has been 

 shown by feeding experiments with laboratory animals that animal 

 and vegetable stearins (melting above body temperature) are only 



1 U. S. Dept. Agr. Bui. 310 (1915). 



