BULLETIN 503, U. S. DEPARTMENT OF AGRICULTURE. 



c5*;5iu^>7/ap /no/? co/^/=>,^/?/so//' 





/Poor C£L£:/py tc//pa///=> o///oa/ 



I I I 



e<5'3 o/iao/p/jsis /s*o ca7^o/p/£'s epo o^^.o/^/£^ 



B/?r/^o /^/L/r 



I 



Fig. 2. — Energy value of edible portion of root vegetables per pound. Just as a> 

 engine must have fuel as a source of the power it supplies, so the body, which is 

 a living engine, uses its food as fuel to supply the energy for the work it per- 

 forms. For measuring the energy value of food the calorie is the most con- 

 venient unit. It represents in round numbers the amount of heat required to 

 raise 1 pound of water from 0° to 4° F., and equals very nearly 3,087 foot- 

 pounds. If it be assumed that the large square at the head represents 1,000 

 calories, the amount of energy which a pound of the different succulent vege- 

 tables would supply is shown in graphic form by the black rectangles used for 

 comparison. These values are, in general, low as compared with such a food as 

 bread. Nevertheless, the succulent root vegetables as a group contribute ma- 

 terially to the energy value of the diet in addition to furnishing material for 

 the structural needs of the body. They are especially important for the mineral 

 elements they supply, and in this respect rank high in comparison with other 

 kinds of food. 



