INACTIVATION OF VITAMIN A BY RANCID FAT 1 
By Wilmer C. Powick 
Associate Biochemist, Bureau of Animal Industry, United States Department of 
Agriculture 
INTRODUCTION 
There is, perhaps, little need to be concerned with the character¬ 
istics of rancid fat as a human food, since by reason of its impala- 
tability and its unsoundness it is already under the ban of the 
consumer, producer, and food inspector alike. Nevertheless it has 
seemed desirable, in the course of studies on rancidity, to carry on 
a few feeding experiments with rancid fats, partly in order to satisfy 
a somewhat prevalent curiosity concerning their wholesomeness and 
partly because of the possible bearing of the results on animal 
nutrition. 
No attempt has been made to evaluate the effect of slightly rancid 
fats fed in small quantities, as this would probably have entailed a 
longer study than the importance of the subject seemed to warrant. 
The chief concern has been rather to discover whether the develop¬ 
ment of rancidity tends to impair the food value of a fat, and infor¬ 
mation along this line has been sought by the shortest route possible, 
viz, by tne feeding of intensely rancid fats in comparatively large 
quantities. 
GENERAL PROCEDURE 
Three experiments, in which sweet and rancid lard were fed to 
white rats, were conducted. In each experiment a number of rats 
selected for uniformity as to age, weight, and general health were 
divided into two lots, in such manner that each rat in the first lot 
should have, as far as possible, its counterpart as to sex and parentage 
in the second lot. One group, used as controls, was fed a ration 
which was adequate to all intents and purposes and which contained 
from 16 to 25 per cent of fresh lard, while the other group was given 
a similar ration containing a corresponding amount of intensely rancid 
lard. Each rat was confined in a separate cage, which was cleaned 
at frequent intervals. About twice a week the weight of each rat 
was charted. In case of the rats receiving the fresh lard, the rations 
were renewed before any noticeable rancidity had developed in the 
old ration; and in all cases both the new and the residual rations 
were weighed when the rations were renewed. 
The two lots of fat employed in these experiments were good grades 
of kettle-rendered lard that had been prepared under observation at 
a local rendering plant and transported directly to the laboratory in 
completely filled glass-stoppered bottles. In each case part of the 
lard, in its original containers, was stored in the dark at 34° F., 
while the remainder was transferred to a large flask placed before a 
light window, where for a period of several weeks it was melted and 
1 Received for publication April 30, 1925, issued January, 1926. 
Journal of Agricultural Research, 
Washington, D. C. 
( 1017 ) 
Vol. XXXI, No. 11 
Dec. 1, 1925. 
Key No. A-104 
