A group of scientists has broken a popular myth that consuming more salt will make your thirsty. A study found that eating salty food diminishes thirst while increasing hunger, due to a higher need for energy. This new study was carried out during a simulated mission to Mars. It was found that ‘Cosmonauts’ who ate more salt in the simulation retained more water, were not as thirsty and needed more energy.
Researchers, including those from the German Aerospace Centre (DLR) in Germany, sealed two groups of 10 male volunteers into a mock spaceship for two simulated flights to Mars.
The first group was examined for 105 days, the second over 205 days. Both groups had identical diets except that over periods lasting several weeks, they were given three different levels of salt in their food.
The results confirmed that eating more salt led to a higher salt content in urine. The increase was not due to more drinking – in fact, a salty diet caused the subjects to drink less. Salt was triggering a mechanism to conserve water in the kidneys, researchers said.
The prevailing hypothesis had been that the charged sodium and chloride ions in salt grabbed onto water molecules and dragged them into the urine, researchers said.
However, the new results showed something different: salt stayed in the urine, while water moved back into the kidney and body.
Experiments in mice hinted that urea might be involved. This substance is formed in muscles and the liver as a way of shedding nitrogen, researchers said.
In mice, urea was accumulating in the kidney, where it counteracts the water-drawing force of sodium and chloride. However, synthesising urea takes a lot of energy, which explains why mice on a high-salt diet were eating more, researchers said.
Higher salt did not increase their thirst, but it did make them hungrier. Also, the human ‘cosmonauts’ receiving a salty diet complained about being hungry.