~Method of Estimating the 100 Calorie Portion.~--The number of calories yielded by 100 grams of food material is taken as a basis upon which to estimate the 100 calorie portion, and X represents the number of grams required to yield this portion. The problem is one of "simple proportion," for example, take the 100 grams of milk just estimated, we found that 100 grams (or c.c.) furnished 69.2 calories of heat, then, 100:69.2 :: X:100--145; or 145 grams of milk are required to furnish 100 calories of heat. Suppose it is desirable to substitute eggs for a part of the milk in the diet, eggs have a higher fuel value per unit of weight than milk, their average composition being 13.4% protein, and 10.5% fat (no appreciable amount of carbohydrates), 100 grams of eggs would yield 100 x .134 = 13.4 x 4 = 53.6 calories from protein 100 x .105 = 10.5 x 9 = 94.5 calories from fat, or a total of 148 calories. The Standard or 100 calorie portion of eggs would be, 100:148 :: X:100 = 68 or the number of grams required to yield 100 calories. Thus it is seen that in using the fuel value of a hundred grams of food material for estimating the standard or 100 calories portion the extremes are always the same. Hence, the weight of the 100 calorie portion may always be obtained by multiplying the extremes and dividing the result by the number of calories furnished by 100 grams of food material. PROBLEMS (a) Compare the fuel value of the various common food materials. (b) How does the fuel value of a chicken salad compare with that of fruit salad? (c) Figure the fuel value of a cupful of cream of tomato soup and compare it with that furnished by the same quantity of beef broth. (d) Weigh and measure a 100-calorie portion of spinach and compare it with a 100-calorie portion of sweet potato. FOOTNOTES: [15] For full description and methods used, see "Journal of The American Chemical Society," July, 1903. [16] "Chemistry of Food and Nutrition" (revised edition), by Sherman. [17] "Chemistry of Food and Nutrition," by Sherman. [18] "Chemistry of Food and Nutrition" (revised), by Sherman. [19] See Table of Standard or 100 Calorie Portions, in Appendix. CHAPTER III THE FOOD REQUIREMENTS OF THE BODY The human body, as far as can be judged, does not use one nutrient to the exclusion of another, but science has proved that the best results are obtained from diets balanced to suit the needs of the body, providing the fuel and repair materials in the amounts which are calculated to give the maximum value with the minimum expenditure on the part of the organism. For while no two individuals are exactly alike, there are factors which govern or influence the food requirements of all, and thus make it possible to estimate the needs of the body with a fair degree of accuracy.