In the seemingly never-ending academic debate on drinking to thirst or drinking to full, there is some new research suggesting our brains can gently inform us when we have had enough.

“THIS isn’t hard to swallow. Our body can influence the amount of fluid we put in our body by making it easier or more difficult to gulp down drinks.

A study by Michael Farrell at Monash University in Melbourne, Australia, and his colleagues has found that swallowing is effortless when we are dehydrated, but more difficult if we have drunk plenty, putting us off from drinking any more.

The team asked volunteers to rate the sensation of taking a sip of water when they were mildly dehydrated, as well as after they had been asked to drink as much water as they were comfortably able. Their ratings for how much effort it took to swallow rose from one out of 10, to about five.

Brain scans showed that when people were over-hydrated, swallowing was linked to more activity in some parts of the brain that are responsible for conscious thought processes (PNAS, DOI:10.1073/pnas.1613929113).

“It shows we have very subtle mechanisms for regulating the amount we drink,” says Farrell. “If left to your own devices, you will drink the requisite amount of water to maintain balance.” (New Scientist, 2017, p.16).

“Drinking represents a crucial behavior that subserves the survival of species by maintaining fluid balance within the body. The present study confirms in humans the presence of swallowing inhibition after excess liquid has been drunk, revealing a mechanism important for the regulation of fluid intake. The findings presented here support the view that swallowing inhibition is probably a “hard-wired” process that aids maintenance of fluid balance within the body, thereby avoiding the detrimental effects of overdrinking that can cause water intoxication and eventually death.” (Pascal et al., 2016).

References

New Scientist (2017) In Brief: Thirsty Throats Drink More Easily. New Scientist. 15 October 2016.

Sakera, P., Farrell, M.J., Egan, G.F., McKinley, M.J. & Dentona, D.A. (2016) Overdrinking, Swallowing Inhibition, and Regional Brain Responses prior to Swallowing. Proceedings of the National Academy of Sciences of the United States of America (PNAS). 113(43), pp.12274–12279. doi:10.1073/pnas.1613929113.