_Milk is the greatest source of calcium (lime)._ Lime is one of the components of food that serves two purposes; it is both building material for bones and regulating material for the body as a whole, helping in several important ways to maintain good health. It is essential that everyone have a supply of lime and particularly important that all growing infants, children, and young people have plenty for construction of bones and teeth. There is almost none in meat and bread, none in common fats and sugars, and comparatively few common foods can be taken alone and digested in large enough quantities to insure an adequate supply; whereas a pint of milk (whole, skim, or buttermilk) will guarantee to a grown person a sufficient amount, and a quart a day will provide for the greater needs of growing children. Whatever other foods we have, we cannot afford to leave milk out of the diet because of its lime. Under the most favorable dietary conditions, when the diet is liberal and varied, an adult should have _at least_ half a pint of milk a day and no child should be expected to thrive with less than a pint.
_Milk contains a most varied assortment of materials needed in small amounts_ for the body welfare, partly for constructive and partly for regulating purposes. These are rather irregularly distributed in other kinds of food materials. When eggs, vegetables, and cereals are freely used, we are not likely to suffer any lack; but when war conditions limit the number of foods which we can get, it is well to remember that the more limited the variety of foods in the diet the more important milk becomes.
_Milk will take the place of bread, butter, sugar, and other foods used chiefly for fuel._ The body is an engine which must be stoked regularly in order to work. The more work done the more fuel needed. That is what we mean when we talk about the food giving "working strength." A farmer and his wife and usually all the family need much fuel because they do much physical work. Even people whose work is physically light require considerable fuel. A quart of milk will give as much working force as half a pound of bread, one-fourth of a pound of butter, or six ounces of sugar. And this is in addition to the other advantages already mentioned.