The traditional wisdom is that eating more salt in your diet increases your thirst and the amount of water you take in, since the sodium dries you out. But while that may be true in the short term, over a longer period, a high-salt diet actually increases the body’s conservation and production of water, according to a new study.
The scientists at Vanderbilt University and in Germany found that the heretofore counterintuitive nuances of salt intake on diet could change our perception of health diets, according to the two papers in the latest Journal of Clinical Investigation.
“We have always focused on the role of salt in arterial hypertension,” said Jens Titze, the senior author, an associate professor of medicine and molecular physiology and biophysics. “Our findings suggest that there is much more to know – a high salt intake may predispose to metabolic syndrome.”
One of the studies focused on the sodium intake of Russian cosmonauts. (The dozen subjects were in a hermetically-sealed simulation space for 105 days and 520 days). The men drank less water when their salt intake increased from six to 12 grams a day during the course of training from 2009 to 2011.
The follow-up study involved mice. The scientists demonstrated that more salt caused a state in which the body is driven by glucocortinoids that break down muscle protein. That protein is then converted into urea by the liver, allowing the body to better preserve water as the liver excretes the excess salt.
The dehydration is therefore avoided through a kind of muscle wasting. But the body could also bring in more energy through eating to expel the salt. The cosmonauts were indeed hungrier with the double-salt diet.
“This predisposes to overeating,” added Titze.
The new dynamic shown by the trials shows that obesity, diabetes, and heart disease could all be affected by reduced sodium diets in unexpected ways, they explained.