In a study carried out as part of a simulation of space travel to Mars, an international team of scientists found that salty diets resulted in less water consumption—the opposite of the common expectation—and a higher demand for food. The simulated mission allowed scientists to carefully monitor food and water intake for months at a time.
The increased hunger appears to be linked to how the body handled the additional salt in foods; it created urea, which accumulated in the kidneys and counteracted salt’s ability to attract water, helping to keep water inside the body. “But synthesizing urea takes a lot of energy,” said the Max Delbruck Center for Molecular Medicine, which found similar results in mice and humans. “The human ‘cosmonauts’ receiving a salty diet complained about being hungry.”
The Delbruck Center said, “The new findings change the way scientists have thought about the process by which the body achieves water homeostasis—maintaining a proper amount and balance.” Researchers from the Delbruck Center, the German Aerospace Center, Vanderbilt University, and other institutions published their results in The Journal of Clinical Investigation.