Drinking too much water may cause brain swelling: experts

Drinking too much water can cause excess fluid accumulation, leading to dangerously low sodium levels in the blood or hyponatremia - a life-threatening condition that can result in brain swelling, scientists warn.

A team from the Research Institute of the McGill University Health Centre (RI-MUHC) in Canada uncovered a key piece to the puzzle of how our brains detect hyponatremia and regulate overhydration.

A study, published in the journal Cell Reports, unearths the fundamental mechanism of how hyponatremia is detected in the brain.

"Our specific data will be important for people studying hydromineral and fluid electrolyte homeostasis, and clinicians who treat patients faced with hyponatremia," said Charles Bourque, from RI-MUHC.

This condition is more common in elderly patients and can cause cognitive problems and seizures in this vulnerable group. While it remains uncertain how hyponatremia develops, a defect in the hydration sensing mechanism of the brain could be the culprit.

Researchers showed overhydration activates Trpv4, which is a cellular gatekeeper implicated in maintaining the balance of water in the body.

Trpv4 is a calcium channel that can be found in glial cells, which are cells that act to surround hydration sensing neurons.

"Our study shows that it is in fact glial cells that first detect the overhydrated state and then transfer this information to turn off the electrical activity of the hydration sensing neurons," said Bourque.

The researchers also found that it is the release of the amino acid taurine that acts to inhibit hydration sensing neurons. Essentially, when overhydration is detected by glial cells, the Trpv4 channel triggers the release of taurine, which acts as a trip wire to inhibit hydration sensing neurons.

The brain's ability to detect excess hydration is essential to maintaining fluid balance in the body and preventing conditions like hyponatremia.

"Preclinical models of hyponatremia will be used to examine if the mechanism we report is affected in this condition with the long-term objective of designing new treatments or diagnostic tools," said Bourque.