This section is from the book "Practical Cooking And Serving", by Janet McKenzie Hill. Also available from Amazon: Practical Cooking and Serving: A Complete Manual of How to Select, Prepare, and Serve Food .
Water is that which slakes thirst and replaces the fluid loss of the body (Hoy); while food is that which replaces the solid loss of the bodyj While water and food would seem to be two separate and distinct compounds, water, in reality, is one of the largest (in amount) components in food and is rightfully classed as one of the Five Food Principles. The primal office of water is the slaking of thirst: thirst is the outward and visible sign that water is needed to carry on the functions of the body, to eliminate waste and to carry nutritive material where it is needed. By its evaporation on the surface water also regulates the temperature of the body. It is often said that those who drink water freely take on flesh. Water is not a nutrient, though it enters into the composition of every bodily tissue, but when water is imbibed freely and at the proper time the functions of elimination and nutrition are generally well carried out, and a condition of health is noted. Those who drink little water are liable to the formation of waste products faster than they are removed. Four pints of water are required daily by the average adult, less than one third of which is supplied in food. Many an individual who rises in a languid state in the morning need seek for no other relief than in a glass of water on retiring at night. This washes the waste products into the proper eliminating channels and insures a fresh and vigorous condition of body in the morning. The remedial effects of hot water are well known. Water, either hot or cold, preferably hot, is also of advantage, if it be taken upon rising, or at least an hour before eating; thus taken it washes out the stomach, and prepares it to receive food. Taken just at the meal time, before the lining of the stomach has time to absorb it, digestion is impeded by the weakening of the digestive fluids.