Researchers found that “astronauts” who ate more salt retained more water
In a study carried out during a simulated mission to Mars, researchers found that “astronauts” who ate more salt retained more water, weren’t as thirsty, and needed more energy.
Researchers from the German Aerospace Centre (DLR), the Max Delbrück Centre for Molecular Medicine (MDC), and Vanderbilt University examined the connection between salt intake and drinking using a mock flight to Mars.
Scientists have known that increasing a person’s salt intake stimulates the production of more urine – it has simply been assumed that the extra fluid comes from drinking.
Nature has apparently found a way to conserve water that would otherwise be carried away into the urine by salt
They simulated a long space voyage using an environment in which every aspect of a person’s nutrition, water consumption, and salt intake could be controlled and measured.
The studies were carried out by Dr Natalia Rakova from the Max Delbrück Centre for Molecular Medicine and colleagues, and used two groups of ten male volunteers sealed into a mock spaceship for two simulated flights to Mars.
The first group was examined for 105 days, the second over 205 days, and had identical diets except that over periods lasting several weeks, they were given three different levels of salt in their food.
As expected, the results confirmed that eating more salt led to a higher salt content in urine and found a correlation between amounts of salt and overall quantity of urine.
Eating more salt led to higher salt content in urine
But the increase wasn’t due to more drinking – in fact, a salty diet caused the subjects to drink less, triggering a mechanism to conserve water in the kidneys.
The project revises scientists’ view of the function of urea in our bodies.
Prof. Friedrich C. Luft, Managing Director of the Charité University Hospital, Berlin, said: “It’s not solely a waste product, as has been assumed.
“Instead, it turns out to be a very important osmolyte – a compound that binds to water and helps transport it.
Salty diet caused the subjects to drink less
“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.”
Before the study, scientists had believed that the charged sodium and chloride…