Chapter XII 



DIET AND NUTRITION 

 by Elmer V. McCollum 



WHAT we know about the nutritive needs of the human 

 body and about quality in foods is the result of 

 experimental studies on animals, correlated with such 

 observations as can be made on human subjects. Between 

 1840 and about 1905, an adequate diet was generally 

 described as consisting of appropriate proportions of 

 proteins, carbohydrates, fats, mineral salts, and water. 

 Oxygen of the air should have been regarded as a nutrient 

 principle, since without it food could not be utilized; 

 but it was not ordinarily included in the list, except as it 

 formed part of the molecules of the foods ingested. Since 

 this date, our knowledge of dietary requirements has 

 advanced materially, and is still advancing, though perhaps 

 nearing completion. The most profitable method of study 

 has been found in efforts to simplify the diet, in order to 

 learn what chemical substances are indispensable, and 

 which of the compounds known to occur in the tissues are 

 capable of being synthesized by the body. 



Proteins consist of giant molecules which are resolved 

 during digestion into about twenty relatively simple 

 organic compounds known as amino-acids. We know that 

 two of these can be synthesized by the body, and, pending 

 further investigations, we may assume that the remaining 

 eighteen must be supplied by the food. We must have the 

 sugar glucose, which may be taken as such or derived from 

 cane or milk sugar or from the various starches. These are 



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