Vol.. 7, 1921 PHYSIOLOG Y: LA NGWORTHY A ND HOLMES 
119 
THE EFFECT OF A VARIATION IN MILLING ON THE DIGESTI- 
BILITY OF WHEAT FLOURS 
BY C. F. IyANGWORTHY AND ARTHUR D. HOI^M^S 
Contribution from the Office of Home Economics, U. S. Department of 
Agriculture 
Communicated by W. A. Noyes, February 16, 1921 
Introduction. — Cereals are almost universally the great source of carbo- 
hydrate food in the human ration, and with moderate additions of fat 
and protein they are capable of sustaining life and health over long periods 
of time. They may be stored for years with little deterioration in quality, 
are easily transported and yield the greatest amount of food for the labor 
expended in producing them. Of the cereal grains, wheat, largely be- 
cause of its gluten content which causes it to produce superior bread 
making flour, has come to be considered as an almost indispensable article 
of diet throughout Western Europe and America. The normal, annual 
per capita consumption of wheat in this country is approximately five 
bushels. 1 Valuable as wheat is in the human dietary in normal times, it 
is even more important in times of stress, for a disturbance in the bread 
supply has an immediate and often harmful effect on national morale. 
The shortage in the food supply of the world in 1917 made the collec- 
tion and correlation of data concerning human nutrition of utmost im- 
portance and many matters were re-examined in the hope of providing 
additional data of value. Extensive investigations of the chemical com- 
position, digestibility, and nutritive value of wheat and wheat products 
have been made by European investigators and in the United States. 
Earlier investigations of this Office, undertaken with the cooperation of 
the Maine and Minnesota Agricultural Experiment Stations, included 
studies of the digestibility of wheat flours prepared under a variety of 
milling conditions from wheat grown under uniform climatic, seasonal 
and soil conditions. The results 2 obtained showed that the protein of 
white flour (72% extraction) was 88.1% digested, that of entire wheat 
flour (85% extraction) was 81.9% digested, and that of graham flour 
(100% extraction) was 76.9% digested. While the data were sufficient 
to permit general conclusions regarding the effect of variation of milling 
on digestibility, the unprecedented world shortage of food during the 
World War made rigid economy in the use of food materials necessary 
and in 1917 the U. S. Food Administration requested this Office to secure 
additional data concerning the relative digestibility of flours representing 
a series of extractions from the same lot of wheat. The results obtained 
from the work thus undertaken were available to the Food Administration 
during the war period. The findings, however, are not limited in their 
application to special conditions under which the work was carried out bu t 
