Effectiveness of rehydration with green tea on recovery from dehydration
| ISRCTN | ISRCTN53057185 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN53057185 |
| ClinicalTrials.gov (NCT) | Nil known |
| Clinical Trials Information System (CTIS) | Nil known |
| Protocol serial number | 19-32 |
| Sponsor | Nara Women's University |
| Funders | ITO-EN, Ltd, Nara Women's University |
- Submission date
- 30/03/2023
- Registration date
- 12/04/2023
- Last edited
- 21/08/2023
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Other
Plain English summary of protocol
Background and study aims
Maintaining hydration by drinking fluid is one way to prevent heat-related illness in a hot environment. Caffeine-containing beverages, including green tea (GT), have been avoided as rehydration beverages because caffeine has been assumed to exert a diuretic/natriuretic action (increase urination). However, the influence of caffeine intake on urine output is not well documented in dehydrated individuals. The aim of this study is to examine the effect of fluid replacement with GT on body fluid balance and kidney water and electrolyte handling in dehydrated individuals.
Who can participate?
Healthy men and women aged over 20 years in the Nara or Kansai area
What does the study involve?
Participants attend the laboratory for three trials. No alcohol or salty food should be consumed for at least 24 hours. Before reporting to the laboratory participants are asked to eat a light breakfast (a box of Carolie Mate, Otsuka) and drink a bottle of water (560 ml). After voiding and keeping a seated position for 30 min, participants will provide a urine sample and a fingertip blood sample and their body weight is measured. Then, participants are dehydrated by performing four bouts of stepping exercise for 20 minutes separated by 10 minutes of rest.
After the exercise, participants keep a seated position for 30 minutes after the end of exercise at a room temperature of 25 °C. At the end of the equilibrium period, measurements of hemoglobin concentration, blood sampling for plasma sodium concentration, urine sampling and measurement of body weight are performed. After these measurements, participants are asked to drink water, green tea, or caffeinated water equal to the volume of fluid lost during the dehydration protocol. Urine sampling and body weight measurement are performed 0.5, 1 and 2 hours later, and hemoglobin concentration and plasma sodium concentration are also measured after 2 hours.
What are the possible benefits and risks of participating?
Participants will benefit from receiving their own personal rehydration profile. Dehydration induced by exercise in heat may be uncomfortable, and participants may feel tired and thirsty, but the dehydration level induced by this protocol is relatively small and the exercise intensity is low. Participants are allowed to quit the experiment whenever they do not want to continue. Participants may also experience a little discomfort during blood sampling from the finger. An experienced person will do this to minimise any discomfort.
Where is the study run from?
Nara Women's University (Japan)
When is the study starting and how long is it expected to run for?
November 2019 to September 2022
Who is funding the study?
ITO EN, Ltd, and Nara Women's University (Japan)
Who is the main contact?
Dr Akira Takamata, takamata@cc.nara-wu.ac.jp
Contact information
Scientific
Kitauoya Nishimachi
Nara
630-8506
Japan
 ORCID ID |
0000-0002-3790-3487 |
|---|---|
| Phone | +81-742-20-3469 |
| takamata@cc.nara-wu.ac.jp |
Study information
| Primary study design | Interventional |
|---|---|
| Study design | Interventional randomized cross-over study |
| Secondary study design | Randomised cross over trial |
| Study type | Participant information sheet |
| Scientific title | Effect of fluid replacement with green tea on body fluid balance and renal responses under mild thermal hypohydration |
| Study objectives | Rehydration with green tea does not cause excessive diuresis/natriuresis |
| Ethics approval(s) | Approved 22/11/2019, extension approved 14/12/2020, Review Board on Human Experiments of Nara Women’s University (Kitauoya Nishimachi, Nara, 630-8506, Japan; +81 (0)742 20 3338; kenkyou@cc.nara-wu.ac.jp), ref: #20-37 |
| Health condition(s) or problem(s) studied | Hydration status monitoring |
| Intervention | After baseline measurement, subjects were dehydrated by performing four bouts of stepping exercise for 20 min separated by 10 min of rest. They were asked to ingest an amount of water (H2O), GT, or caffeinated H2O (20 mg/100 ml; Caf-H2O) that was equal to the volume of fluid loss during the dehydration protocol; fluid balance was measured for 2 h after fluid ingestion. Randomization was performed using randomization.com. |
| Intervention type | Other |
| Primary outcome measure(s) |
1. Fluid balance is calculated from the change in body weight measured with an electric balance for 2 hours of the dehydration period and 2 hours after the ingestion of fluids. Body weight measurements are performed at baseline, immediately after the dehydration period, 0.5, 1 and 2 hours after fluid ingestion. |
| Key secondary outcome measure(s) |
1. Urinary flow rate calculated from the weight of sampled urine, in which subjects were asked to empty the urinary bladder, and the time between sampling. Urine collections are made at baseline, immediately after the dehydration protocol, and 0.5, 1, and 2 hours after fluid ingestion. |
| Completion date | 30/09/2022 |
Eligibility
| Participant type(s) | Healthy volunteer |
|---|---|
| Age group | Adult |
| Lower age limit | 20 Years |
| Sex | All |
| Target sample size at registration | 12 |
| Total final enrolment | 13 |
| Key inclusion criteria | 1. Healthy young male and female volunteers 2. Age >20 years 3. BMI 18-25 kg/m² 4. No known cardiovascular, renal or metabolic disease |
| Key exclusion criteria | 1. Overweight or obese (BMI >25 kg/m²) 2. Current or former cardiovascular, renal or metabolic disease 3. Currently taking prescribed medication |
| Date of first enrolment | 01/02/2020 |
| Date of final enrolment | 31/08/2022 |
Locations
Countries of recruitment
- Japan
Study participating centre
Nara
630-8506
Japan
Results and Publications
| Individual participant data (IPD) Intention to share | Yes |
|---|---|
| IPD sharing plan summary | Available on request |
| IPD sharing plan | The datasets generated and/or analyzed during the current study will be available upon request from Akira Takamata (takamata@cc.nara-wu.ac.jp) |
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Results article | 18/08/2023 | 21/08/2023 | Yes | No | |
| Participant information sheet | Participant information sheet | 11/11/2025 | 11/11/2025 | No | Yes |
Editorial Notes
21/08/2023: Publication reference added.
05/05/2023: The following changes have been made and the plain English summary updated accordingly:
1. The overall trial end date has been changed from 30/09/2023 to 30/09/2022.
2. The intention to publish date has been changed from 01/05/2023 to 01/09/2023.
12/04/2023: Trial's existence confirmed by the Review Board on Human Experiments of Nara Women’s University.
