NUTS AS FOOD. 85 



DISCUSSION OF RESULTS. 



It has been found that the nutritive value of all foods, irre- 

 spective of their source or kind, depends upon the presence of 

 one or more of four classes of nutrients. These are called pro- 

 tein (nitrogenous matter), fats, carbohydrates and ash (mineral 

 matter). The gluten of wheat, the lean of meat, the white of an 

 egg and the curd of milk (casein), are all familiar illustrations 

 of protein. These matters differ from other food constituents 

 in that they contain nitrogen. Examples of fats are butter (fat 

 of milk), the fat of meat, the oils of plants and seeds, as olive 

 oil, oil of corn, etc. Carbohydrates consist of starch, sugar 

 and allied substances. They make up the greater portion of 

 such foods as potatoes and corn. Ash is the matter left after 

 burning, and so far as nutrition is concerned, consists chiefly of 

 phosphates and chlorides of lime, potash and soda. 



Food has in general two distinct uses in the body : one to 

 build up and repair, the other to supply the energy needed to 

 enable the body to do work, maintain its temperature, etc. The 

 living tissues of the body, with the exception of fatty tissues, are 

 built up entirely from protein and ash. Protein can be used by 

 the body as a source of energy, but the fats and carbohydrates 

 are the chief sources of energy under normal conditions. The 

 body cannot create energy, but is dependent upon the potential 

 energy of its food for the work it does. The food yields up its 

 energy to the body by being burned, just as truly as if it were 

 in a furnace under a boiler. 



As above stated, protein can be burned by the body as a source 

 of energy. This, however, is wasteful of protein, as energy is 

 much more economically furnished by fats and carbohydrates. 

 Not only are the fats and carbohydrates burned as a source of 

 energy, but being thus oxidized in the body they partially protect 

 the protein of the food and of the body from being burned. 



Since the chief use of protein is to build up and repair the 

 animal body, if it were protected so that none of it were oxidized 

 only a small amount of protein would be needed per day for 

 maintenance of the body. As it is, even with an abundance of 

 fats and carbohydrates in the food, quite considerable amounts 

 of protein are daily oxidized. The amount of protein that is 



