Regulering van waterinname

Body hydration is a balance between water intake and output.

An adult typically gains 2.5 L of water per day primarily through food and drink and metabolic reactions within cells, maintaining the plasma osmolality at 280 to 300 mOsm.

Increased plasma osmolality triggers thirst and the release of antidiuretic hormone or ADH for water conservation.

Conversely,  a decrease in plasma osmolality suppresses both thirst and ADH release, producing dilute urine.

Thirst, controlled by the hypothalamic thirst center, is the primary driver of water intake.

The thirst center is usually activated by a 1-2% increase in extracellular fluid osmolality, dry mouth, or a significant decrease in blood volume or pressure.

The sensation of thirst subsides almost instantly after drinking water. Liquid intake moisturizes the mouth and throat mucosa and activates osmoreceptors and stretch receptors in the stomach and small intestine.

Conversely, individuals with conditions like primary polydipsia constantly feel thirsty despite adequate fluid intake, leaving them hyperhydrated.