The argument in favor of two meals a day has been that the digestive system is inactive during sleep, and, therefore, the system is not ready for a meal upon arising, but the latest experiments (Pawlow) show that digestion continues during sleep, though less actively. It must be borne in mind that the average evening meal is eaten about six o’clock and that there are about four waking hours between this meal and the sleep period; also, that the average individual is awake and moderately active an hour before the morning meal. This gives five waking hours between the evening and the morning meal. About the same time, five hours, elapses between the morning and the midday meal, and between the midday and the evening meal, so that three meals a day divide the digestion periods about evenly.
More frequent meals, served in lighter quantity, with greater regularity, so that the system is not overloaded at any one meals, is rational for delicate, or undernourished nerves and tissues. The little child is fed regularly every three hours.
Effect of Exercise and Breathing upon Digestion
Daily exercise and the habit of full breathing are absolutely necessary that the waste of the system may be fully liberated, that the nourishment may be carried freely to every tissue, and that sufficient oxygen may be carried through the blood to oxidize the waste, or, to put it into condition to be thrown off.
The necessity of oxygen as food is evident. The body will subsist about forty days upon the food stored within it, without re-supply, but it can endure only a few seconds without oxygen, because heat, occasioned by the union of oxygen with carbon and hydrogen, is necessary to keep up the physical activity termed “life.” The necessity of habits of full, correct breathing cannot be too fully emphasized. The quantity of oxygen, daily consumed, should fully equal the sum of all other food elements.[6]
Oxygen is necessary to cause combustion of fats, starches and sugars, just as it is necessary to cause combustion of carbon in wood, or coal.
The heat from “burning” wood is produced by the oxygen of the air uniting with hydrogen and carbon, forming carbon-dioxid (carbonic acid gas) and water.
The light in the burning of wood is caused by the rapid combustion of the carbonic acid gas. The same combustion occurs within the body continuously, though more slowly, hence no light is produced.
The carbon in the body is liberated and brought into contact with more oxygen in the blood through exercise and full breathing, just as a fire is fanned to flame by bringing more oxygen into contact with the fire, by means of a draught of air. Keep all air away from a fire and it “goes out,” or ceases to unite with the oxygen, and no heat is produced; keep all air from within the body, by cessation of breathing, and it also becomes cold. A room in which the air is impure, containing insufficient oxygen, is heated with difficulty,—the body which is not constantly supplied with pure air generates very little body heat. The effect of oxygen in the creation of heat is practically demonstrated by repeatedly filling the lungs with air while out in the cold. The body will become quickly warmed on the coldest day by this practice.