Water is the basis of growth and the maintenance of health for all living things.
Although water has been taken for granted, the lack of it can cause death more rapidly than any other nutrient. It has been established that a human being can survive up to two weeks without food, but cannot survive more than three days without water.
Water makes up approximately 60% of our body weight. However, much of that is lost through excessive exercise, diarrhea, urination, perspiration, bleeding, exhaled air etc. etc. That is the reason we are required to drink two to four liters a day to substitute for that loss.
The intake of water is regulated by the body which provides signals in different ways:
- Thirst is felt in the mouth by a dry feeling resulting from decreased saliva. In the case of severe diarrhea, perspiration, excessive urination etc. saliva will cease to be released .
- When water intake drops, the hypothalamic cells stimulate the release of an antidiuretic hormone to store body water by decreasing the production of urine, causing water retention. When water intake returns to normal, the same cells reduce release of the antiduiretic hormone and water retention is relieved.
- The pituitary glands, located at the center of the brain, as well as renal functions, regulate plasma volume by conserving or releasing water as necessary.
Severe dieting or forced starvation and a carbohydrate-restricted diet cause severe water loss of upto 1.5 liters.
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