Sodium citrate, stress hormones and cycling in the heat
What it found
In 20 male athletes, taking sodium citrate during recovery after dehydrating exercise led to lower aldosterone and cortisol levels before and after a 40 km cycling time trial in the heat.
It made no difference to prolactin or growth hormone.
What they found
Studies in people
Aldosterone levels
In the sodium citrate trial, aldosterone levels were 72% lower before and 39% lower after the time trial compared to placebo. The rise in aldosterone during exercise was also 29% smaller with sodium citrate.
Cortisol levels
Cortisol levels were 13% lower before and 14% lower after the time trial in the sodium citrate trial compared to placebo. However, the increase in cortisol during exercise was similar in both trials.
Prolactin and growth hormone
There were no differences between the sodium citrate and placebo trials in prolactin or growth hormone levels before or after the time trial. The increases during exercise were also similar.
Performance and temperature
Total work and time to complete the 40 km time trial were similar in both trials. The rise in core body temperature during exercise was smaller with sodium citrate (2.45 °C vs 2.62 °C).
Blood glucose and lactate
Blood glucose fell more during the time trial with sodium citrate, dropping below pre-exercise levels. Blood lactate rose more with sodium citrate, reaching 7.58 mmol/L compared to 5.58 mmol/L with placebo.
Plasma volume
Before the time trial, plasma volume was 6.9% above pre-dehydration levels with sodium citrate but 0.9% below with placebo. After exercise, plasma volume was 6.2% below pre-dehydration levels with sodium citrate and 12.5% below with placebo.
What the authors conclude
“CIT compared to PLC ingestion during 16 h recovery period after DE results in decreased blood ALDO and CORT levels prior to and during subsequent cycling TT in a warm environment in male non-heat-acclimated endurance athletes.”
Also in their conclusions
- They conclude that reduced aldosterone and cortisol levels after the time trial, and the blunted aldosterone response, indicate that sodium citrate ingestion during recovery after dehydrating exercise may alleviate stress during a subsequent hard endurance cycling bout in the heat.
- They state that sodium citrate ingestion has no influence on blood levels of prolactin or growth hormone in these conditions.
- They suggest that reduced stress during exercise may lead to improved recovery, and that this possibility deserves further research.
How it was done
The authors wanted to test whether sodium citrate, which has been shown to reduce exercise stress in temperate conditions, would also reduce stress hormone responses during prolonged exercise in the heat.
Twenty non-heat-acclimated male endurance athletes lost 4% of body mass by exercising in the heat. During a 16-hour recovery, they ate prescribed food and took either sodium citrate (600 mg per kg) or a placebo in a double-blind, randomised, crossover design with 7 days between trials. Blood levels of aldosterone, cortisol, prolactin and growth hormone were measured before and after a 40 km cycling time trial in a warm environment (32 °C).
What it can’t tell you
- This was a single exercise-recovery-exercise cycle, so it cannot show what happens over multiple days of competition.
- The study did not measure hormone and glucose levels before and after the dehydrating exercise, so it cannot show those changes.
- The study did not have definite data on blood acid-base balance or electrolyte levels, so it cannot confirm how those factors contributed.
Who paid
- Funding
- Funded by Estonian Ministry of Education and Research (from the PubMed record).
- Conflicts
- The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
- Authors work at
- University of Tartu, Estonia; Tartu University Hospital, Estonia
The paper
- Title
- Influence of Sodium Citrate Supplementation after Dehydrating Exercise on Responses of Stress Hormones to Subsequent Endurance Cycling Time-Trial in the Heat
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Suvi S, Mooses M, Timpmann S, Medijainen L, Unt E, Ööpik V (2019). Influence of Sodium Citrate Supplementation after Dehydrating Exercise on Responses of Stress Hormones to Subsequent Endurance Cycling Time-Trial in the Heat. Medicina (Kaunas, Lithuania). doi:10.3390/medicina55040103Free full textPubMed 31013820DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error