Historical Concepts of Protein and Energy

Early reports of what may have been PEM lack the clinical, pathological, and biochemical details that make identification certain. The history of PEM is thus confined to the nineteenth and twentieth centuries, and it is only in the last 50 years that clarification of the various forms that PEM can manifest has emerged.

In his book Protein and Energy, Kenneth J. Carpenter has provided a detailed survey of nutritional science as it was known in the period from 1614 to 1893 (Carpenter 1994: 1-99). Of particular interest in relation to later discoveries is that the first “balance studies” were carried out by Italian scientist S. Santo-rio in 1614. He weighed his food and drink as well as his excreta (urine and feces) and measured changes in his own weight. There was an unexplained daily disappearance of 5 pounds of material that he attributed to a breakdown of body tissue that was then secreted through the skin as insensible perspiration; the losses were made good by the nourishment ingested. This was only a more quantitative restatement of Galen’s view in the second century that “[o]ur bodies are dissipated by the transpiration that takes place through the pores in our skins that are invisible to us; therefore we need food in a quantity proportionate to the quantity transpired” (Carpenter 1994:1).

Anton Lavoisier’s work in the late eighteenth century (1770 to 1790) made him the “Father of Nutritional Science.” His first contribution was the recognition of the distinction between compounds that could change their character and simple substances or elements (e. g., carbon, hydrogen, nitrogen, oxygen, and others). His second contribution was an understanding that combustion and respiration involved similar processes of oxidation that could explain the phenomenon of “animal heat.”

Among those who followed Lavoisier was Jean-Baptiste Boussingault, who published the first table of the nitrogen content of foods in 1836. The protein radical was discovered just two years later by Gerrit Mulder and was considered to be the essential ingredient for both body building and physical activity. By the end of the nineteenth century, however, it was realized that protein was not the main or obligatory source of energy and that it is the oxidation of carbohydrates and fatty acids on which we rely for continued physical work.