..not thirsty as is widely believed, according to a study carried out during a simulated mission to Mars by an international group of scientists and published in The Journal of Clinical Investigation The study was based on two separate groups of 10 male volunteers who were sealed into a mock spaceship for two simulated flights to Mars-one group for 105 days, the other for 205. The volunteers had identical diets except for their salt intake. They were given three different levels of salt in their food.

 

A salty diet actually caused the participants to drink less water. Salt triggered a mechanism in the kidneys to conserve water, making the participants less thirsty But the men reported feeling more hungry when their salt levels were higher, even though their calorie intake was the same. This may be because it takes extra energy for the body to conserve water. I do think that if we’d offered the cosmonauts more food, they would have overeaten and gained weight,” said the study’s senior author.