More than half the weight of the human body is water. Water is the basis of all body fluids, including digestive juices, blood, urine, lymph, and perspiration. All cell processes and all organ functions depend on it. It is essential as a lubricant: as the basis of saliva, mucous secretions throughout the body, the fluid that bathe the joints.
Water is needed to keep food moving through the intestinal tract and to eliminate wastes; it helps prevent constipation, which may occur if you're eating high-fiber foods without sufficient water. Water also helps regulate body temperature by distributing heat and cooling the body via perspiration.
The body loses and needs to replace, under average circumstances, two to three quarts of water every day. If you're exercising or doing physical work in the heat, the loss can be much more.
We get some water from foods we eat, especially fruits and vegetables, most of which are 85% to 95% water. Some water is produced as a by-product of metabolism. But six to eight glasses of liquid - including milk, juices, and soups - are usually needed to make up the balance. Alcoholic and caffeinated beverages (coffee, tea, and colas) are not ideal for this purpose because they have a diuretic effect - that is, they increase urine production.
The best source is generally plain water. With all the ballyhooed claims we hear and read about beverages, foods and nutritional supplements, it's easy to forget the benefits of a glass of H2O. (And remember that you need to be cognizant of drinking water even in the wintertime. You are not as aware of perspiration loss in dry indoor environs, because perspiration evaporates as fast as it is secreted.)
