Page:The story of milk.djvu/167

 3.25% protein, 4% fat and 5% milk-sugar, has a nutritive ratio of 1 : 4.3, i. e., 1 part of protein to 4.3 parts of heat-giving nutrients, counting the fat equal to 2-1/4 of carbohydrates (multiplying the 4% fat by 2-1/4 makes 9, added to the 5% of sugar, makes 14; 3.25 to 14 equals 1 to 4.3). Skim milk, containing 3.4% protein, 0.2% fat, and 5.1% sugar, has a ratio of 1 : 1.6 (3.4 : 5.45). Mother's milk, containing 2% protein, 4% fat, and 6.5% carbohydrates, has a ratio of 1 : 7.75. To substitute cow's milk for mother's, it must therefore be "modified."

Calories.—Another way of comparing various foods than by the nutritive ratio is by measuring their "fuel value" or energy-producing capacity. The amount of heat required to raise the temperature of one kilogram of water 1° C., or one pound 4° F., is called a calorie. By extensive feeding experiments the caloric value of the various nutrient groups has been estimated as follows:

Protein at 1820 calories per pound Fats    " 4040       "   "    " Carbohydrates at 1820 calories per pound

Measured by this rule the fuel value of:

Whole milk is        310 calories per pound Skim milk  "         160    "      "   " Full cream cheese is 1885   "      "   " Butter is            3410    "      "   "

Compared with other food, milk, although not suited to act as the sole food of adults, is one of the best and