Frank I. Katch


Santorio experiments breakthrough
in energy metabolism


Russel Henry Chittenden (1856-1943)
Chittenden excelled in chemistry at Yale's Sheffield Scientific School, where his senior project investigated why leftover scallops tasted sweeter when recooked. Chittenden discovered that muscle tissue contained large amounts of free glycogen. With encouragement from his mentor, Chittenden published his paper in the American Journal of Science in 1875, and republished in a British and German journal (Vickery, 1947).

After graduation, Chittenden traveled to Heidelberg, where he worked with the notable enzyme chemist Wilhelm Kühne (1837-1900; first to refer to organic catalysts as "enzymes" in 1878). Surprisingly, Kühne had read Chittenden's article on glycogen in scallops. In his memoirs, Chittenden recalled:

The atmosphere had changed, and my spirits rose accordingly, reaching a still higher level when Kühne remarked that he would find a place for me in the laboratory at once....After a month in the laboratory, Kühne asked me if I would like to serve as his assistant in the lecture demonstrations.

Chittenden attended classes in advanced chemistry (given by Professor Robert W. Bunsen--the Bunsen burner bears his name), anatomy, surgery, and pathology, and visited German laboratories where he met distinguished researchers. The year's experience at Heidelberg resulted in three publications and influenced his approach to science. In 1880, Chittenden received the first PhD degree in physiological chemistry from an American university (Yale). Two years later, he became Professor of Physiological Chemistry at Sheffield, a post he held for the next 40 years.

Chittenden published 144 scientific papers, including a text on nutrition with special reference to protein requirements (Chittenden, 1904). This text refocused attention on the minimal protein requirement while resting or exercising, and influenced future research in nutrition and exercise physiology. After studying laborers who consumed approximately 3100 kcal (13 MJ) daily, the distinguished German physiologists Carl Voit (1831-1908) and Max Rubner (1854-1932) maintained that protein intake should be either 118 g per day (Voit) or 127 g per day (Rubner); the American chemist Wilbur O. Atwater (1844-1907) recommended a protein intake similar to Rubner's. Recommendations for protein intake were even higher for soldiers doing hard physical labor (Voit 145 g; Rubner 165 g; Atwater 150 g). In contrast, Chittenden's experiments contradicted these figures because they showed that no debilitation occurred in normal and athletic young men (including himself) subsisting on low protein diets.

Young male subjects performing strenuous gymnastic exercise during a year long experiment at Yale University on the effects of "minimal" protein intake on upper and lower body muscular strength and various measures of physical fitness.

Two Yale athletes of many who maintained muscularity despite what was considered by European nutritionists as suboptimal protein intake (about 0.9 g/kg body mass per day). The European advocates of a high protein intake believed that strenuous daily workouts on a low protein intake would cause the muscular system to weaken, making subjects look emaciated. Chittenden included these photographs to emphasize that consuming minimal protein as part of the total daily food intake would not diminish muscularity.

Chittenden's data included daily dietary and urine histories to determine nitrogen excretion (protein utilization). For nine months, he recorded his own body weight. Although it decreased from 65 to 58 kg, and his daily protein intake was one third of what Voit recommended to maintain nitrogen equilibrium, Chittenden's health remained excellent without compromising physical vigor or muscular tone. In a year-long study, athletic men in excellent health on a low protein diet (less than 1 g per kg daily) likewise suffered no deterioration of health or ability to perform arduous physical tasks. Chittenden's data proved that, even without a large protein intake, individuals could maintain their health and fitness. Chittenden summarized his findings:

In presenting the results of the experiments, herein described, the writer has refrained from entering into lengthy discussions, preferring to allow the results mainly to speak for themselves. They are certainly sufficiently convincing and need no superabundance of words to give them value; indeed, such merit as the book possesses is to be found in the large number of consecutive results, which admit of no contradiction and need no argument to enhance their value. The results are presented as scientific facts, and the conclusions they justify are self-evident.


Chittenden, R. H. (1904). Physiological economy in nutrition, with special reference to the minimal protein requirement of the healthy man. An experimental study. New York: Frederick A. Stokes Company.

Vickery, H. B. (1947). Russel Henry Chittenden. Biographical memoirs, XXIV. Washington, DC: National Academy of Sciences.

Copyright ©1998
Edited by Mary Ann Wallace
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