DIGESTIBILITY OF WHEAT BRAN. 5 
It is sometimes contended that test periods of three or four days’ 
duration are too short to give reliable data regarding the digestibility 
of foods. Newman and Robinson,’ who question the accuracy of re- 
sults of digestion experiments of only three days’ duration, studied the 
relative digestibility of white flour and whole meal (flour prepared 
from whole wheat kernel) breads of which 700 to 800 grams were 
eaten with 600 cubic centimeters of milk and 30 grams of butter fat 
daily for a period of two weeks. As a result of four experiments in 
which, with one exception, the protein of white flour was more com- 
pletely digested, they found that on the average the protein of white 
flour was 89.3 per cent digested while the protein of whole meal was 
85.9 per cent digested. They also report that the digestibility of the 
protein of a wheat meal (92 per cent of the kernel) was 76.7 per cent 
as compared with a digestibility of 80.4 per cent for the protein of 
another wheat meal (88 per cent of the wheat kernel). 
Experiments conducted by Hindhede? to determine the relative 
digestibility of coarsely ground wheat as compared with ordinary 
white flour are not open to this criticism, since they were of seven 
months’ duration. He found that the protein of coarsely ground 
wheat (bread) eaten with margarine was 75 per cent digested while 
the protein of ordinary wheat flour eaten in a similar diet was 85 
per cent digested. In both instances the total carbohydrate was 
found to be practically completely digested. 
Additional evidence regarding the effect on digestibility of in- 
cluding bran in flour is available in the reports of several investi- 
gators. Inasmuch as the experimental conditions employed in the 
tests of the digestibility of wheat flours made by the European in- 
vestigators were not uniform, it is perhaps not possible to make as 
direct comparisons as in the case of the American studies. In 
general, considering the results of these investigations as a whole, it 
is apparent that the protein of flours containing a relatively small 
proportion of bran is more completely digested than the protein 
present in flours which contain a large proportion of bran. 
In order to secure additional] evidence regarding the effect on 
digestibility of including bran in flour Snyder * conducted two series 
of three digestion experiments each comparing digestibility of 
the protein of straight-grade flour and the digestibility of the pro- 
tein of the same flour to which he added 14 per cent of finely ground 
bran (the amount of bran which he assumed to be normally present 
in graham flour). His results were as follows: The digestibility 
of bread from the flour with the bran was for protein 85.9 per cent 
1 Jour. Hyg. [Cambridge], 12 (1912), No. 2, pp. 132, 134. 
2Skand. Arch. Physiol., 33 (1916), pp. 263-290; abst. in Chem. Abs., 12 (1918), No. 1, 
p. 54. 
#U. 8. Dept. Agr., Office Expt. Stas. Bul, 156 (1908-1905), p. 42. 
