It’s long been recognized that salt makes people thirsty. After all, you can’t eat a bag of salt and vinegar chips without downing a glass of water. Simple, right? Well, perhaps not so much.
Researchers conducting a study during a simulated mission to Mars recently discovered that subjects who consumed more salt were actually less thirsty in the long run. They were, however, also more hungry.
Up until now, studies suggested that the intake of more sodium led to the production of more urine (it was assumed that the extra fluid resulted from drinking more). But the new study put together by researchers from the German Aerospace Center, the Max Delbrück Center for Molecular Medicine in Germany and Vanderbilt University in Tennessee found that subjects who upped their salt intake from six grams to 12 grams ended up drinking less.
The study followed 10 males who were voluntarily sealed into a fake spaceship for two simulated trips to the fourth rock from the sun. The first group was inside for 105 days, and the second for 205. While everyone got the same rations, their salt intakes ranged between three different levels.
Contrary to popular belief — that salt dragged water into the urine — eating a high-salt diet surprisingly triggered the kidney’s ability to conserve water. Researchers now suspect that water can be stored in the kidneys thanks to another biological hero: urea, which was initially believed to be nothing more than the body’s waste.
“[Urea turned] out to be a very important osmolyte — a compound that binds to water and helps transport it. Its function is to keep water in when our bodies get rid of salt. Nature has apparently found a way to conserve water that would otherwise be carried away into the urine by salt,” said Friedrich Luft, one of the study’s lead authors.
The subjects in the study then became hungry in order to replenish the energy used by the body’s urea. And if you think about it, this makes a lot of sense. Because the only thing people usually want more than a glass of water after eating salty chips is more chips.