16 BULLETIN" 468, IT. S. DEPARTMENT OF AGRICULTURE. 



than the bread that the 6 pounds of potatoes furnish decidedly less 

 protein and fat and slightly less carbohydrates than the 2 pounds of 

 bread. It is easy, therefore, to see why, in spite of their cheap- 

 ness and similar composition, they should not occupy the same place 

 in the diet as bread. A diet of bread alone would be rather too one- 

 sided for the best development of bodily powers, but would come 

 nearer to supplying the required protein without excess of carbo- 

 hydates than potatoes alone. 



With respect to the total nutritive material they supply, raw pota- 

 toes resemble fresh fruits, such as bananas and apples, with their 

 seven or eight parts of water to one of food substance, more than they 

 do such foods as uncooked flour or rice, with their one part of water 

 to nine of nutritive material. Since raw potatoes consist of only 

 one-fifth and raw rice, for instance, of seven-eighths nutritive mate- 

 rial, one would naturally say that rice is more than four times as 

 nutritious as potatoes, and this is true of them as they are bought in 

 the market. This, however, is not the case when they are compared 

 in the state in which they appear on the table. When rice is cooked 

 water is added to it, with the result that when it is eaten it is not 

 very different in composition from cooked potatoes ; thus a pound of 

 boiled rice and a pound of mashed potatoes would have very much 

 the same total fuel value, a fact which has been intuitively recognized 

 by housekeepers, who often use them interchangeably to serve with 

 meats, etc. They do not, however, have the same effect on the 

 alkalinity of body tissues and fluids. . 



According to generally accepted standards, a man at moderately 

 active work requires about one-fourth pound of protein a day, along 

 with sufficient fats and carbohydrates to give the total food an energy 

 value of about 3,500 calories. It would take about 9 pounds of 

 potatoes to furnish this energy, but that quantity would yield much 

 less protein than the amount called for by the standard. About 19 

 pounds of potatoes would be needed to yield the required 0.25 pound 

 of available protein, an obviously impossible bulk for a day's ration. 

 Except under stress of necessity, however, few persons try to live 

 entirely or even principally on potatoes. Ordinarily they are eaten 

 with other foods rich in protein, such as meat, milk, eggs, etc., and 

 thus they supplement these nitrogenous foods by furnishing the 

 needed carbohydrates in an easily digested form. 



The abundant mineral matters which they contain also supply the 

 body with important building materials and help to regulate its proc- 

 esses. As is the case with most vegetables and fruits, potatoes, when 

 they have been digested and assimilated by the body, tend to make 

 the tissues and fluids of the body more alkaline. Meats and eggs, 

 on the other hand, tend to make them more acid, while the cereals 

 (including rice) do not affect them greatly either way. Physiolo- 



