In adulthood the body is no longer centered on growing and dividing cells. The hydration requirement levels are able to reach a stable number. The body’s job now is simply to regulate the water that is coming in. This doesn’t mean drinking less water; it means keeping the water levels where they need to be. The thirst signal starts to diminish in adulthood. This is because the body learns to ration water in dehydration mode and there is no need for the thirst mechanism. Rationing water during hydration is obviously not the goal of our water cycle. It is a survival trait of the body’s functions.
The body recognizes that some functions are more important than others and cells then receive water on a “need” basis only. When cells do not need the water, blood vessels leading to them are shut down and circulated to other more important cells. Between ages 18-25 the body starts its thirst sensation reduction. Dr. Batmanghelidj elaborates: “Unfortunately, our thirst sensation, as it is understood today—a dry mouth—is not an accurate indicator of the body’s actual water needs. If we don’t feel thirsty, we tend not to drink water. We wait to become thirsty before we even begin to think of drinking water.” To sum it up, the body needs more than it asks for. Drinking water before thirst sets in is important.
Reference: “Water for Health, for Healing, for Life” by F. Batmanghelidj, M.D.