


AVAILABILITY AND FUEL VALUE OF FOOD MATERIALS. 83 
and fish, 6 per cent. by eggs and 12 per cent. by dairy prod- 
ucts, making a total of 61 per ¢ent. from animal food materials. 
Of the remaining 39 per cent. which came from the vegetable 
food materials, 30 per cent. was supplied by the cereals, 2 per 
cent. by the dried legumes, 6 per cent. by garden vegetables 
including potatoes, and 1 per cent. by fruits. More than go 
per cent. of the fat was of animal origin, and more than half 
came from meats, while nearly one-third was furnished by 
dairy products. - On the other hand only a little over one- 
twentieth (5.5 per cent.) of the carbohydrates was of animal 
origin, while 55 per cent. came from the cereal products. It is 
a little surprising to note that over one-fifth of the total carbo- 
hydrates in these 185 dietaries studied was furnished by cane 
sugar, molasses, etc. 
How closely these figures represent the average diet it is 
impossible to say. There is a large proportion of the popula- 
tion of the southern states, including the bulk of the colored 
people and of the poorer whites in the country districts, who 
live mainly upon corn meal, fat pork and molasses. ~ A consid- 
erable number of dietaries of the people of these districts have 
been studied, but they are not included in the 185 studies 
above summarized. ‘There may be other exceptions also, but 
it seems to us probable that these figures in Table 3 are not 
very far from a fair representation of the actual distribution of 
the different food materials and nutrients in the average diet of 
persons of the industrial, commercial, and professional classes 
in the United States. 
THE AVAILABILITY OF THE DIFFERENT CLASSES OF 
NUTRIENTS IN FOOD OF MIXED DIET. 
The value of food for nutriment depends not only upon the 
total amounts of nutrients but also upon the amounts which 
the body can make available for its support. The proportions 
of the different nutrients which the body can digest and utilize 
from different food materials are learned by digestion experti- 
ments. Such experiments involve the accurate measurement 
of the amounts of the different kinds of nutrients consumed in 
the food during a given period and the corresponding amounts 
excreted in the feces. ‘his last material is made up of the 
