Can drinking too much water harm you?

Do you drink too much water? Beware, overhydration -- excess fluid accumulation -- can lead to dangerously low sodium levels or in the blood or result in brain swelling, researchers say.

Hyponatremia, a life-threatening condition of brain swelling, is more common in elderly patients and can cause cognitive problems and seizures. "(Hyponatremia) occurs in common pathological conditions, including brain injury, sepsis, cardiac failure and in the use of drugs, such as MDMA (ecstasy)," said Charles Bourque from the McGill University in Canada.

While it was yet uncertain how hyponatremia develops, the study found that a defect in the hydration sensing mechanism of the brain could be the culprit.The researchers said that brain's hydration sensing neurons could not detect overhydration in the same way that they detect dehydration.

Overhydration activates Trpv4 -- a calcium channel that can be found in glial cells, that act to surround hydration sensing neurons.

It is cellular gatekeeper implicated in maintaining the balance of water in the body.
"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," Bourque explained.

"Our specific data will be important for people studying hydromineral and fluid electrolyte homeostasis, and clinicians who treat patients faced with hyponatremia," he noted.

The results, published in the journal Cell Reports, showed that overhydration is first identified by the Trpv4 channel which triggers the release of a type of amino acid known, taurine, which acts as a trip wire to inhibit hydration sensing neurons.

"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," Bourque added.