Anyone who has ever ordered a large popcorn just for themselves knows that gobbling delicious handfuls of salt makes you thirsty. Or does it? New research on Russians training for space travel has turned everything we know about sodium on its head — in fact, the results appear to indicate that eating salt actually makes you not thirsty at all, but hungry.
"[The study] is just very novel and fascinating," kidney specialist Dr. Melanie Hoenig told The New York Times.
Cosmonauts live in highly controlled facilities to simulate the experience of traveling in space, and scientists dedicate long hours to studying participants' physiology. Dr. Jens Titze first noticed curious and unexplainable fluctuations in crew members' urine levels in 1994, and in 2006 he got a chance to explore his hypothesis.
Titze realized that when crew members ate high-sodium diets, they drank less in the long run but their urine volume increased, indicating bodies were producing water when salt intake was high. By experimenting on mice, Titze realized that the more salt he doled out, the less water the animals drank as increased levels of glucocorticoid hormones worked to break down fat and muscle to produce water internally. Because such a process requires a lot of energy, though, salt led both the crew members and mice to eat more food when on high-salt diets.
But what about that popcorn? Dr. Mark Zeidel, who wrote a companion editorial to Titze's study, told The New York Times that "people and animals get thirsty because salt-detecting neurons in the mouth stimulate an urge to drink. This kind of 'thirst' may have nothing to do with the body's actual need for water."