DIET
April 25, 2017

Salt Makes You Hungry, Not Thirsty

A set of new findings has completely changed our understanding of what too much salt does to your body.

The age-old belief that salty food makes you thirsty and causes you to drink more just got turned on its head. Instead, two studies provide evidence for the idea that salty food causes us to eat more and makes us less thirsty.

Two groups of Russian cosmonauts who were on a simulated mission while preparing for a potential manned spaceflight to Mars were used in one of the studies. U.S. and German researchers fed the men diets that contained between six, nine and 12 grams of salt per day. Everything they ate and drank was recorded, and their urine was collected.

The findings from these studies could shed a whole new light on the treatment of obesity, heart disease, diabetes and osteoporosis.

Conventional wisdom says that after eating excess salt, body water is lost when the excess salt is excreted in the urine, causing us to drink more. But these long-term sodium balance studies found that the body’s response to eating too much salt is contrary to the principles of sodium balance taught in textbooks.

When the amount of dietary salt was increased from six to 12 grams per day, the men drank less water, suggesting that instead of excreting water, the men’s bodies were conserving and producing water.

There are a number of steps to this process, as an animal study by some of the same researchers showed. It found that high salt intake caused a state of muscle wasting in the body that was fueled by glucocorticoids, hormones that are notorious for breaking down muscle tissue. The by-product of muscle wasting, urea, allowed the kidneys to reabsorb and conserve body water as the salt was flushed from the body.

However, the loss of muscle tissue requires the body to expend a lot of energy to avoid dehydration, so the body requires extra fuel — which means eating more. This could explain why the Russian cosmonauts complained of hunger as their sodium intake was increased.

High levels of glucocorticoid hormones, a result of water conservation, are considered an independent risk factor for obesity, heart disease, diabetes, and osteoporosis. The findings from these studies could shed a whole new light on the treatment of these diseases.

The focus on salt has always been in relation to high blood pressure, but, according to Jens Titze of Vanderbilt University, one of the researchers, these findings suggest that there is a lot more to learn.

The studies are published in the Journal of Clinical Investigation.
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