Salt intake, water drinking and body water balance in people and mice
What it found
Long-term high salt intake did not make people or mice drink more water.
Instead, their bodies held onto more water.
What they found
Studies in people
Drinking less, retaining more
In cosmonauts on a high-salt diet, fluid intake went down rather than up. Their bodies held onto free water instead of relying on extra drinking to handle the salt load.
Hormones shifted with salt
Salt and water balance in the cosmonauts changed along with natural rises and falls in stress-related hormones called glucocorticoids and mineralocorticoids.
Animal and lab studies
Urea helped hold water
In mice, eating more salt led to more urea building up in the kidneys. This came from breaking down more protein and helped the body keep the water it needed.
Kidney proteins increased
Mice on high salt diets also made more urea transporters in the inner part of the kidney. These proteins helped move urea around to support water retention.
What the authors conclude
- They say these findings overturn the old idea that handling extra salt is just a simple matter of drinking more water.
- The authors note that keeping salt and water balanced involves hormones, metabolism, eating, drinking and kidney function working together.
- They suggest future research should map out the brain circuits behind this process to help treat conditions like high blood pressure.
How it was done
Scientists long believed that eating more salt simply made people thirstier so they would drink enough to flush it out. The authors wanted to explain two studies showing the process is actually much more complex.
The author reviewed two studies: one followed Russian cosmonauts during a simulated long space mission, and the other tested mice. Both looked at how the body handled long periods of high salt intake.
What it can’t tell you
- This text describes two specific studies rather than testing a new treatment, so it cannot show what happens across all people eating high-salt diets.
- The mouse experiments reveal how animal kidneys work, but those exact steps may differ in human bodies.
Who paid
- Conflicts
- Conflict of interest: The author has declared that no conflict of interest exists.
The paper
- Title
- Salt and water: not so simple
- Type
- Study
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Zeidel ML (2017). Salt and water: not so simple. The Journal of clinical investigation. doi:10.1172/JCI94004Free full textPubMed 28414294DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error