It is economy to keep the digestive organs and the circulation and tissues strong, in order that all foods eaten may yield returns, instead of hampering the activity of the body. The food which furnishes the most tissue-building substance and yields the most heat and energy, with the least refuse, is the economical food, provided it is varied enough to meet the psychical needs as well as the physical. Whether or not a food is economical depends on the degree to which it stimulates the activity of the mind as well as the body. Preparation and serving here are as important as the material to be served. Economy in food is a question into which many factors should enter. A cheap food is not always an economical food. Amount and keeping qualities, palatability, ripeness or unripeness, the age, habit, and occupation of the partakers, all have their share in the problem. In the selection of food for any individual, the result to be gained from the food must be borne in mind. If one is doing heavy muscular work, more protein to rebuild tissue, as well as more carbohydrates and fats to produce energy, are required than if one’s habits of work are sedentary. In mental work, in which the brain is continually active, proteins are required to resupply the brain tissue, but the fats and carbohydrates may be lessened. If the brain is sufficiently active to use all of the fuel in brain energy one does not accumulate fat. In sedentary occupations, which do not call for hard and continuous mental activity, the carbohydrates and fats, if taken in excess, are stored within the system, clogging it and producing torpid liver, constipation, and obesity. In a study of tables of food values, in making up a dietary, the question should be to provide the largest quantity of nutriment at the lowest cost, with due attention to palatability and variety. In the selection of meats, for instance, while beef steak may cost twice as much as beef stew, it must be borne in mind that beefsteak contains very little waste, and that it contains a large proportion of albuminoids, or the tissue-building proteins, while, in beef stew, bone and connective tissue predominate. A large proportion of the proteins obtained from the beef stew are gelatinoids and extractives—not the tissue-building albuminoids. (See page 56.) In comparing the cheaper and the more expensive cuts in the same kind of beefsteak, however, the cheaper cuts often yield quite as much nutriment as the more expensive ones. Round steak is just as nourishing as porterhouse and cheaper, if one considers the greater number of helpings derived from a pound of round steak than from a pound of porterhouse. For the aged or the invalid, however, the question of preparation will determine the relative economy. FOOTNOTES: