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October 14, 1916


JAMA. 1916;LXVII(16):1165-1166. doi:10.1001/jama.1916.02590160043018

The answer to the question as to what constitutes a food is becoming more complicated with the development and expansion of our knowledge of metabolism and nutrition. A few years ago the method to be pursued in finding the solution to such a query seemed clear. It was merely necessary to ascertain whether the substance in question could yield energy, not merely in a laboratory apparatus but also in the living organism. The reservation here indicated was necessary for the reason that many substances, which will burn up outside of the body to furnish heat and work, do not digest when ingested by the organism itself, and hence cannot enter the tissues proper to participate in metabolism; or they may be positively toxic, despite their combustibility. Cellulose readily yields heat in the bomb calorimeter; but it passes through the alimentary tract of man unchanged. Its energy is not available, as