PROCEEDINGS 
OF THE 
NATIONAL ACADEMY OF SCIENCES 
Volume 7 JUNE 15, 1921 Number 6 
FEEDING EXPERIMENTS WITH MIXTURES OF FOODSTUFFS 
IN UNUSUAL PROPORTIONS* 
By Thomas B. Osborne and Lafayette B. Mendel 
Connecticut Agricultural Experiment Station, and the Sheffield Laboratory 
of Physiological Chemistry in Yale University 
Read before the National Academy of Sciences, April 26, 1921 
Ever since Magendie 1 announced, in 1816, that the protein group of 
foodstuffs represents an indispensable component of the dietary of the 
higher animals, students of nutrition have been interested in the part 
played by the other nutrients that commonly enter into our food intake. 
Are fats or carbohydrates or both equally essential for successful nu- 
trition? We pointed out some time ago that the reason why there is no 
available information respecting the actual requirement of the healthy 
mammal for fat is attributable to the experimental difficulties heretofore 
inherent in its solution. 2 Until the significance of the accessory food 
factors now known as vitamines was appreciated studies of the physiolog- 
ical value of mixtures of different foodstuffs, etc., were liable to lead to 
failure and erroneous conclusions, not because the supply of energy or 
protein or salts was inadequate but because other unrecognized and un- 
identified essentials were lacking. 
Since it has become possible, by taking account of these various newly 
appreciated properties of foods, to devise rations in which essentially 
one factor at a time may be altered, the investigation of the role of the 
individual nutrients has become more promising. Accordingly we have 
already succeeded in raising young animals (albino rats) from an early 
age to adult size on diets which were exceptionally poor in fats. 
The food mixtures consisted of the residues from extracted lean meat 
as a source of protein, starch, inorganic salts, together with small quanti- 
ties of alfalfa and dried brewery yeast furnishing the vitamins A and B. 
Analyses of the rations consumed indicated that the maximum intake 
of fat at any time did not exceed 0.3 per cent of the food eaten. Inasmuch 
as all the animals starting on the diet with a body weight of approxi- 
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