An excess of proteins, that is, more than is needed for building and repair, is also used for heat and energy.
The waste products of the nitrogenous foods are broken down into carbon dioxid, sulphates, phosphates, and other nitrogenous compounds, and excreted through the kidneys, skin, and the bile, while the waste product of carbonaceous foods is largely carbon dioxid and is excreted mostly through the lungs.
Since the foods richest in protein are the most expensive, those who wish to keep down the cost of living, should provide, at most, no more protein than the system requires. Expensive meats may be eliminated and proteins be supplied by eggs, milk, legumes, and nuts.
The fundamental thing is to decide on the amount of protein—two to four ounces, nearly a quarter of a pound a day—and then select a dietary which shall provide this and also supply heat and energy sufficient for the day.
If the diet is to include meat, a goodly proportion of protein will be furnished in the lean meat. This will vary greatly with the different cuts of meat, as shown in Table IV, page [54]. If, as often happens, one does not care for fats, then the starches and sugars must provide the heat. If much sugar is eaten less starches and fats are needed.
The normally healthy individual is more liable to take too much protein than too little, even though he abstain from meat.
If the diet is to include meat, it will be of less bulk, because the protein is more condensed; for the same reason, if it includes animal products of eggs and milk and a fair proportion of legumes, it will be less bulky than a vegetable diet. Yet unless vegetables, fruits, and plenty of water are consumed one must guard against constipation. This point is important for busy people who eat their meals in a hurry and proceed at once to active mental work.
Those who engage in physical labor are much more likely to take a complete rest for a half-hour, or an hour, after eating. The thinkers seldom rest, at least after a midday meal, and those who worry seldom relax the mental force during any waking hour; their brains are as active as those of mental workers.
Every housewife, to intelligently select the daily menus for her family, needs a thorough knowledge of dietetics. She must understand the chemistry of food that she may know food values.
The difficulty which confronts the housewife is to provide a meal suited to the needs, tastes, or idiosyncrasies of the various members of her household. Peculiarities of taste, unless these peculiarities have been intelligently acquired, may result in digestive disturbances. As an illustration: one may cultivate a dislike for meat, milk, or eggs, as is often the case, and if the proteins for the family is largely supplied by these, the individual who omits them from the meal, eats too large a proportion of starches and sugars, and not sufficient protein—legumes, nuts, etc. If this is long continued the blood becomes impoverished and anemia is produced.