2 DEPARTMENT BULLETIN 975, U. S. DEPT. OE AGRICULTUEE. 



fairly common.^ There are, however, other essentials in the diet 

 which can not be explained so easily. For example, it has been 

 difficult to make helpful statements about the mineral matters, the 

 more important of which are iron, calcium, and phosphorus. It 

 is fairly well known how much of these are needed by the body and 

 how much are found in different food materials, but in both cases 

 the quantities are so small (only a few grams or even milligrams 

 per man per day or per pound of material) that it is impracticable 

 to measure them by pounds or ounces as we do the food materials 

 that supply them. 



In general, the plan here followed is to make a graphic comparison 

 between a pound of some of the common foods and the daily needs 

 of a man who does moderately active muscular work. No one would 

 think, of course, of trying to live on one food alone, but the com- 

 parison made by the charts is helpful in combining food materials 

 so as to make a complete ration, for it shows not only what a given 

 food supplies but also what it lacks. The milk diagram (p. 20) is a 

 good illustration. A glance at it shows that a pound (pint) of 

 milk would supply 9 per cent of the energy or fuel, 15 per cent of the 

 protein, 80 per cent of the calcium, 32 per cent of the phosphorus, but 

 only 7 per cent of the iron needed daily by a man who does moder- 

 ately active muscular work. Or, to put it another way, if a pint 

 of milk is used in the daily dietary of this man, the remaining foods 

 must supply 91 per cent of the fuel needed, 85 per cent of the protein, 

 20 per cent of the calcium, 68 per cent of the phosphorus, and 93 per 

 cent of the iron. To speak in particular only of the calcium and the 

 iron, which offer a striking contrast, the remaining 20 per cent of the 

 calcium would almost inevitably be supplied by the other foods even 

 if they were selected at random, while it might require some thought 

 to supply the other 93 per cent of the iron. 



In making these comparisons it is assumed that the food supply of 

 a man who does moderately active muscular work should furnish 

 3,500 calories of energy, or body fuel, 100 grams (3| ounces) of pro- 

 tein, 0.68 gram of calcium, commonly called lime, 1.32 grams of 

 phosphorus, and 15 milligrams of iron. This amount of food makes 

 provision for waste, of which a certain amount is unavoidable. It 

 is generally agreed that a properly nourished man doing moderately 

 active muscular work eats daily food that supplies about 3,000 

 calories, and that to be sure of supplying this amount the foods pro- 

 vided for him should furnish about 3,500 calories. The allowance 

 of 100 grams of protein provides a generous margin of safety above 

 the actual jorotein requirement, and the allowances for calcium, 



1 U. S. Dept. Agr., Farmers' Bui. 142, Principles of Nutrition and Nutritive Value of 

 Food ; Farmers' Bui. 808, How to Select Foods. I. What the Body Needs. 



