129. Influence Of Individual Peculiarities

It is a fact of common experience that certain persons do not comfortably digest certain foods, whatever may be the ultimate proportion that is digested. Definite and proven explanations of this fact are not available. It is not improbable that a mental attitude toward a given food sometimes has its influence, although this can hardly explain why certain individuals are made uncomfortable from eating strawberries or pork, or some other food. This may be due to an enzym deficiency in some part of the digestive tract, or to a peculiar reaction upon the individual of particular compounds present in the offending food; but these suggestions are speculative.

130. The Extent To Which Different Classes Of Foods Are Digested

A large amount of experimenting shows that the following are approximately the proportions of the nutrients that are digested in the different classes of foods. These figures refer to apparent digestibility and not to actual. If the metabolic products in the feces were accounted for, the proportions would be higher, especially for protein. The satisfactory separation of the real undigested portion of the food from the accompanying waste products is not yet accomplished.