The latest Popular Science issue discusses the fact that consuming more salt in your diet may not have a direct correlation with drinking more water.
I’m sure you heard that the more salt you eat, the thirstier you get. There are actually two studies published in the Journal of Clinical Investigation disproving this theory. They in fact found that as people had more salt in their diets, they drank less water. Subjects who had a high salt diet made subjects hungrier instead.
Various international groups consisting of the German Aerospace Center, Max Delbrück Center for Molecular Medicine, Vanderbilt University, among other institutions, conducted one of the studies. There were 10 males subjects part of the study to try and understand the effects of isolation on the human body as though it were a mission to Mars. They looked at the psychological and medical risks this kind of mission has for long periods of time while keeping track of their physical and mental state.
The study was conducted over a 105-day period also known as “spaceflight”. The first test was to reduce sodium intake from 12 grams to 9 grams and eventually to 6. They left each salt intake constant for a 29-day period. Obviously liquid consumption was being measured as well as how much they urinate daily.
The results were not as what people generally think where as more salt we consume, the more water we drink. They actually drank less water as they had more salt in their diet. In addition, they peed more and had more salt present in their urine. After testing the urine of each candidate, they found it was more concentrated suggesting the body was holding on to more water.
To understand the association with salt consumption with the human body, researchers turned to mice. They divided up the mice in three groups; one was fed low sodium with tap water, the second were given high sodium and tap water, the third had high sodium with a saline solution. The time span of the study was over a 4-week period. What they found was a component in the body called urea is needed to get rid of nitrogen in the kidneys. Salt counteracts with the water-attracting force of it. For your body to produce urea, it needs energy so researchers found mice of salty diets didn’t drink more but ate more.
Keep in mind that everyone’s bodies are different and these studies were never conducted on women or even female mice. Researchers have more work to do to study the effects of urea on the human body when it comes to helping dispose of salt while still holding onto water.