A Mars simulation reveals salt makes you hungry, not thirsty.
German scientists at the Max Delbrück Center for Molecular Medicine (MDC) studied two separate groups of 10 men during a simulation of a trip to Mars at the German Aerospace Center.
Over 200 days the “cosmonauts” were given identical diets except for their salt intake. Results of the investigations published in the Journal of Clinical Investigation found that a salty diet actually caused the men on the high salt diets to drink less.
The men who ate more salt, retained more water, weren’t as thirsty and needed more energy, according to the findings.
Scientists have known that increasing a person’s salt intake stimulates the production of urine and it has been assumed that the extra fluid comes from drinking more because they were thirsty.
But it now appears that salt triggers a mechanism in the kidney that causes the kidneys to hold onto water and produce urea – a process which consumes energy, causing hunger not thirst.
“Nature has apparently found a way to conserve water that would otherwise be carried away into the urine by salt,” said Freidrich Luft from the MDC.
Studies in mice have previously hinted that the production of urea was responsible for this increased appetite, Luft added.
Urea is a compound and is the end product of protein metabolism. It is formed in the liver and excreted by the kidneys in the urine. It is generally thought of as a waste product but Luft said that’s wrong.
“Instead it turns out to be a very important osmolyte, a compound that binds to water and helps transport it,” said Prof Luft.
“Its function is to keep water in when out bodies get rid of salt.”