31 



graham flour 62.62 per cent; that is, the carbohydrates of the straight 

 patent flour were much more digestible than those of either the entire 

 wheat or graham flour. The amount of available energj^ of the straight 

 patent flour is also krger than that of either the graham or entire- 

 wheat flour. 



On comparing the figures in this table with those previously reported « 

 it will be observed that the results for protein here given are higher. 

 This is due to two facts already pointed out, namely, that the per- 

 centage of protein in the wheat employed in these experiments was 

 higher, and the coefiicients of digestibility were larger. The signifi- 

 cance of the results, however, is the same in Ijoth cases. Briefly stated, 

 the results of all of the experiments with hard spring wheat show that 

 the digestible protein and carbohydrates, as well as the amount of 

 available energy, are greater in the standard patent flour than in either 

 the graham or entire-wheat flour. 



No marked variations in the balance of income and outgo of nitrogen 

 were observed in the different periods except such as were due to 

 differences in the amounts consumed. In other words, judged by the 

 data regarding the metabolism of nitrogen, the three sorts of breads 

 served the bod}" equally well. 



The results of these experiments confirm those of earlier work with 

 hard-wheat flours, and show that when breads made from straight 

 patent flour, entire-wheat flour, and graham flour, milled from the 

 same lot of hard spring wheat, are fed under uniform experimental 

 conditions to men, there is a larger amount of digestible protein and 

 carbohydrates and available energy in the patent flour than in either 

 the entire-wheat or graham flour, although judged by composition the 

 graham flour contains the most and the patent flour the least total 

 protein. The greater digestibility of the protein and carbohydrates 

 of the patent flour is regarded as due in part at least to the fineness 

 of division of the flour particles, or, in other words, to the fact that a 

 considerable portion of the nutrients in the graham and entire-wheat 

 flours are present in comparatively large particles, which resist the 

 action of the digestive fluids and so escape digestion. It has also been 

 suggested that the cell walls in the layer of the grain directly under 

 the bran are more resistant to digestive juices than the walls of cells in 

 the interior of the kernel (see pp. -IS, 49). Thus while there is actually 

 somewhat more protein, pound for pound, in graham or entire-wheat 

 than in patent flour, the body obtains less protein and energy from 

 the coarser than it does from the finer flour, and whatever is gained 

 in composition by adding the bran or germ is offset by the loss in 

 digestibility. 



«U. S. Dept. Agr., Office of Experiment Stations Bui. 101, p. 33. 



