Water, which forms about sixty-six per cent of the human body, is by far the most important substance therein. It comprises the major part of the blood serum and every tissue and organ. If a normal human body weighing 150 pounds were put into an oven and thoroughly dried, there would be left only about 50 pounds of solid matter, all the rest being water. The proportion of water in animal and vegetable substances is also very great. As water is also a conspicuous factor in all foods, either in chemical combination, or in solution with other elements mechanically mixed, it is obvious that water is an important factor in food science.
USES OF WATER IN THE BODY
The uses of water in the body may be roughly grouped into three divisions, as follows:
1 Water in small quantities enters into the actual chemical composition of the body.
As we will notice in the discussion of carbohydrates, water combines chemically with cane-sugar when it is digested and transformed into glucose. (See Lesson IV, "Cane-sugar," page [112.])
2 Water forms a portion of the tissues and acts as a solvent in the body-fluids.
What blood carries in solution
In this function the water is not changed chemically, but is only mixed with other substances; thus the blood is in reality water with glucose, peptone, etc., in solution, and carrying along with them red blood-corpuscles and fatty globules.
3 Water is a most important factor in the digestion, and the assimilation of food, and the elimination of waste.
Drinking with meals
Inasmuch as the body is nearly two-thirds water, it follows that the diet should be composed of about 66 per cent moisture. The old theory of dietitians that no water should be taken with meals was based upon the hypothesis that the water diluted the gastric juice, and that this diluted form of the gastric juice weakened its digestive power. Actual practise has proved this thesis to be untrue. Water is the great universal solvent, and the hydrochloric acid of the stomach is only a helper, as it were, in the dissolution or the preparation of food for digestion.
Water is also a valuable agent in the elimination of body-poisons.
Value of water to blood
The liberal use of water keeps the blood supplied with the necessary moisture, and that excess which is eliminated through the kidneys carries away poisons that would reside in the body very much to the detriment of health. There is little danger, therefore, in drinking too much pure water, but much care should be exercised that it be pure, or at least free from lime and mineral deposits. The best water is pure water, free from all mineral substances.
If a meal consists of watery food, such as fresh vegetables, salads, etc., then the drinking of water becomes unnecessary; but When water drinking is unnecessary where the meal is composed chiefly of solids, then an amount of water should be taken sufficient to make up 66 per cent of the total. If more water is taken than is necessary for this purpose, the excess will pass off and the stomach will only retain the necessary amount; but if the quantity of moisture is insufficient, the stomach calls to its aid an excess of hydrochloric acid, the strength of which has a tendency to crystallize the starch atom (especially cereal starch), thereby causing the blood-crystal, which is one of the primary causes of rheumatism, gout, Disorders caused by insufficient moisture lumbago, arterial sclerosis (hardening of the arteries), and all disorders caused by congestion throughout the capillary and the arterial systems. The most common disorder among civilized people is hydrochloric acid fermentation. Copious water drinking at meals is the logical remedy for this disorder.
The proper amount of pure non-mineral water taken with food will do much to remove the causes of superacidity and the long train of ills that follow this disorder. (See "Chart," Lesson I, page [9.])
In this work I shall constantly refer to these various uses of water, especially as a solvent (an aid to digestion), and as a remedial and curative agent.
Man's source of water
Theories have been promulgated by hygienic teachers in the past few years that man should get his supply of water wholly from the juices of fruits, and not drink ground-waters, which are contaminated with mineral substances. While it may be true that water in certain localities, such as in the alkali deserts, is unfit for drinking, yet the writer believes that the promulgators of the theory that man is not a drinking animal never did a hard day's work in a harvest field. In the dry winds of the western plains water evaporates from the surface of the body at the rate of twelve or fifteen pounds a day. The theory of deriving one's water supply wholly from fruits would not stand the test of such facts.