Salty diets make you hungry, not thirsty, scientists find
Are bar nuts based on a myth? Yes and no, new research shows.
It's conventional wisdom as timeless as beer taps: Eating salty foods makes you thirsty.
But if you inhale fistfulls of bar snacks on a regular basis, you may find the opposite to be true. Diets high in salt can lead the body to retain more water, decreasing thirst and ramping up hunger, according to newly published research in The Journal of Clinical Investigation.
An international group of scientists from places such as the Vanderbilt University and the German Aerospace Center conducted the first-ever study on salt intake and drinking habits, according to the Max Delbrück Center for Molecular Medicine, which also took part.
To create a controlled environment with fixed diets, researchers used two simulated Mars missions involving 10 male volunteers. One "mission" lasted for 105 days and the other for 205 days. The men all ate the same diets, but with differing levels of salt.
At first, the hunch of every bartender held up: Salty foods increased thirst in the short term, according to the Max Delbrück Center. But over the long term, those on salty diets drank less and complained about being hungry more. That's because the salt set off a mechanism that keeps water in the kidneys, researchers found.
While many theorized that salt essentially gloms onto water molecules and pulls them into the urine, the results showed salt staying with the urine while water moved back into the kidneys and body.
It caused scientists to take a closer look at urea, a bodily compound thought to be a waste product, said Friedrich C. Luft, M.D., a doctor with the center.
"Its function is to keep water in when our bodies get rid of salt," Luft said. "Nature has apparently found a way to conserve water that would otherwise be carried away into the urine by salt.”
But making urea takes a lot of energy, which leads to hunger — in mice, at least. That could explain why high-salt subjects experienced increased hunger.
Scientists behind the research said it could shape understandings of how the body achieves proper balance, or homeostasis.