Sodium intake and cortisol measurements in 630 adults
What it found
In 630 adults, a high-salt diet raised the amount of cortisol found in a 24-hour urine sample and slightly lowered morning blood cortisol, compared with a low-salt diet.
What they found
Studies in people
Urine cortisol rose
On the high-salt diet, the average 24-hour urine free cortisol was 178.0 nmol/day, compared with 121.3 nmol/day on the low-salt diet. This was about a 47% increase.
Most people affected
84% of participants had higher urine free cortisol on the high-salt diet than on the low-salt diet.
More above thresholds
Far more people went above set cut-offs for urine cortisol on the high-salt diet. For example, 17% went above 248 nmol/day on high salt, compared with 4% on low salt.
Blood cortisol slightly lower
Morning total serum cortisol was slightly lower on the high-salt diet (303.0 nmol/L) than on the low-salt diet (326.4 nmol/L). 59% of people had lower morning blood cortisol on high salt.
Similar in both groups
The rise in urine cortisol with high salt was seen in people with normal blood pressure and in those with high blood pressure.
What the authors conclude
“Increased dietary sodium intake increases urinary free cortisol excretion and may increase the risk for false-positive results.”
Also in their conclusions
- They say that higher dietary sodium intake increases urinary free cortisol excretion and may increase the risk for false-positive results.
- They advise that doctors consider measuring 24-hour urinary sodium when doing a urine cortisol test, or suggest a moderate sodium intake in the days before the collection.
- They note that an isolated, mildly elevated urine cortisol result does not mean a person has Cushing syndrome.
How it was done
Doctors use a 24-hour urine cortisol test to check for Cushing syndrome, but the result can vary for many reasons. The authors wanted to see whether the amount of salt people eat affects this test.
They studied 630 adults without known Cushing syndrome, heart or kidney disease. Each person ate a low-salt diet (230 mg sodium a day) for 5 to 7 days, then switched to a high-salt diet (4600 mg a day) for 5 to 7 days, with urine and blood tests at the end of each phase.
What it can’t tell you
- The salt levels in this study were more extreme than what people usually eat, so the size of the effect in everyday life may be smaller.
- The study cannot show whether these changes in cortisol measurements lead to different diagnoses or health outcomes.
- The study did not measure some hormones like corticotropin, so it cannot explain the exact reason for the changes.
Who paid
- Funding
- Funded by NHLBI NIH HHS; NIDDK NIH HHS; NCATS NIH HHS (from the PubMed record).
- Conflicts
- Conflicts of Interest: AV reports consulting fees unrelated to the contents of this work from Corcept Therapeutics, HRA Pharma, Orphagen Pharmaceuticals, Catalys Pacific. AV, AXC, AVH and GWH have nothing to disclose
- Authors work at
- Brigham and Women's Hospital, USA; Flinders Medical Centre, Australia; Flinders University, Australia
The paper
- Title
- Dietary sodium intake and cortisol measurements
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Chen AX, Haas AV, Williams GH, Vaidya A (2020). Dietary sodium intake and cortisol measurements. Clinical endocrinology. doi:10.1111/cen.14262Free full textPubMed 32511774DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error