Russel Henry Chittenden (1856-1943)
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:
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.
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:
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.