Two separate groups of 10 male test subjects were sealed in a cosmonaut-like environment - one group for 105 days, the other for 205 - and had identical diets except for their levels of salt. The results, published in The Journal of Clinical Investigation, found that a salty diet caused the test subjects to drink less. Evidently, salt triggers a mechanism in the kidneys to hold onto water and produce urea - a process which eats up energy, causing hunger, not thirst.