28 BULLETIN 468, U. S. DEPARTMENT OF AGRICULTURE. 
wholesome, palatable, and useful food, and can be prepared for the 
table in many acceptable forms without undue labor or fuel. 
The starchy roots are important in nutrition as sources of energy. 
Figure 7 shows in graphic form the energy value of some of the more 
common of such vegetables. 
As the diagram shows, the energy value varies from about 400 to 
600 calories per pound. In general, the drier the root the higher the 
energy value, which means that potatoes, for instance, which have 
been harvested and dried out may have an energy value considerably 
higher than the value here cited as an average. 
CONCLUSION. 
All these starchy tubers and roots — potato, sweet potato, Jerusalem 
artichoke, cassava, yam, dasheen, yautia, and taro — yield the body 
little protein to supply nitrogen needed for building body tissue 
and little energy-producing fat, but on the other hand their fine- 
grained starch and other carbohydrates supply easily digested energy- 
yielding nutritive material and small quantities of valuable min- 
eral matters which help to build the bones and are useful for other 
physiological purposes. Thanks to the ease with which most of 
them are cultivated, they are among the cheaper of our vegetables, 
while their usually mild flavors and the variety of ways in which 
they may be prepared make it possible to serve them in many com- 
binations. They merit their extensive use because they make health- 
ful supplements to other classes of food found in the usual mixed 
diet, and because they are economical and agreeable sources of body 
energy. 
