2 BULLETIISr 1033, U. S. DEPARTMENT OF AGEICULTUEE. 



disease were common and physiologists generally believe that this 

 was due, to some extent at least, to a lack of vitamin A. It should 

 also be remembered that fats and oils represent the most concen- 

 trated source of body fuel, a fact that has an important bearing on 

 the food transportation problem and on the cost of food to the con- 

 sumer. An adequate national food policy therefore requires that an 

 abundant fat supply be maintained during peace times as well as 

 during war, and there is justification for the efforts made to find 

 new sources of food fats and to make better use of those we now 

 have. 



For such reasons the Department of Agriculture has outlined a 

 broad program for the study of edible fats, which includes investiga- 

 tion of the source of supply, methods of production and rectification, 

 the relation of feed to fat production in farm animals, including 

 the cost at which fat is produced at different ages, and the relation 

 of this to the production of meat and dairy products. It also in- 

 cludes studies of the economical use of fat in cookery and its rela- 

 tion to the quality of the cooked product and of the thoroughness 

 of digestion of fats and oils and the tolerance of the body to dif- 

 ferent kinds. These latter aspects of the problem have been for some 

 years under investigation in the Office of Home Economics of the 

 States Eelations Service, cooperation with other bureaus being se- 

 cured whenever this has seemed desirable. 



The digestibility of 60 or more different fats and oils, some of 

 animal and some of vegetable origin, has been tested in the Office of 

 Home Economics. In a few cases, fish oil and avocado fat for in- 

 stance, the fat was not extracted but was eaten as it occurs in these 

 foods as ordinarily served. In most cases, however, the fat was 

 rendered or otherwise freed from the tissue in which it occurs, and 

 if necessary, further purified. These studies have been reported 

 from time to time in publications of this department and in pro- 

 fessional journals.^ This bulletin reports two groups of studies, one 

 with a variety of fats and oils regarding which information -was 

 needed for special reasons, and one with blended hj'drogenated fats 

 such as are now in common use. 



EXPERIMENTAL METHOD. 



The method followed in these experiments was the same as that 

 developed in the previous digestion experiments of this office. No 

 method has yet been devised by which the proportion of nutrients 

 actually digested from any one food material in a mixed diet can be 

 directly measured, and all the methods now in use admit of at least 



»U. S. Dept. Agr. Buls. 310 (1915). 505 (1917),, 507 (1917). 630 (1918). 687 (1918), 

 613 (1919), 781 (1919) ; Jour. Biol. Cbem., 41 (920), No. 2, pp. 227-235; Amer. Jour. 

 Physiol., 54 (1921), No. 3, pp 479-488 



