Fluid Intake, Hydration Status, Psychosocial Stress
Conditions
Brief summary
Over half of the adult population in Europe, Asia and Latin America fail to meet adequate water intake guidelines as advised by the European Food Safety Authority (EFSA; 2.5 and 2 litres/day for men and women, respectively coming from both food and drinks). Increasing epidemiological evidence suggests that chronic low fluid intake may be associated with an increased risk of cardiovascular, metabolic, and renal diseases. The association between chronic low fluid intake and increased morbidity risk may be underpinned by elevations in key water-regulating hormones, such as arginine vasopressin (AVP) and its surrogate copeptin, which influence glucose regulation and renal function. For example, AVP stimulates the hypothalamic-pituitary adrenal (HPA) axis to release the stress hormone cortisol with potentially far-reaching effects on metabolism, immunity and inflammation. Prospective cohort studies have demonstrated that exaggerated cortisol responses to acute stress are associated with poor health outcomes. A recent cross-sectional study (NCT05491122) from our group found that individuals with a low habitual fluid intake experienced greater cortisol reactivity to acute stress than those with a high habitual intake. The findings of this study may provide a potential explanation for why poor hydration and low fluid intake have negative effects on long-term health. We now aim to explore whether altering fluid intake influences cortisol reactivity to acute stress.
Interventions
BEHAVIORALModifying daily total fluid intake
7-day intervention where the intake of drinking water will either be maintained at habitual level, increased (if habitually low) or decreased (if habitually high). The TFI prescriptions during the intervention are derived from the mean TFI of habitually low and habitually high drinkers from a sex, age and country matched population. Specifically, habitually low drinkers will be permitted a TFI of 3.5 L/day for men and 3.3 L/day for women and habitually high drinkers will be permitted a TFI of 1.3 L/day. Participants will be instructed to maintain their usual intake of other beverages i.e., tea/coffee to achieve their target TFI.
Sponsors
Liverpool John Moores University
Unilever R&D
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
NONE
Intervention model description
Participants will be screened to identify habitually low, i.e., total fluid intake: men ≤ 1.6 L/day, women ≤ 1.5 L/day and high i.e., total fluid intake: men ≥ 2.9 L/day, women ≥ 2.5 L/day drinkers. Each subject will undergo two study arms; verification period: 7 days following their habitual daily fluid intake; intervention period: 7-day intervention where daily fluid intake will either be increased (if habitually low), decreased (if habitually high) or maintained at habitual level. The total fluid intake (TFI) prescriptions during the intervention are derived from the mean TFI of habitually high and habitually low drinkers from a sex, age and country matched population. Specifically, habitually high drinkers will be permitted a TFI of 1.3 L/day and habitually low drinkers will be permitted a TFI of 3.5 L/day for men and 3.3 L/day for women. Participants will be instructed to maintain their usual intake of other beverages i.e., tea/coffee to achieve their target TFI.
Eligibility
Sex/Gender
ALL
Age
18 Years to 35 Years
Healthy volunteers
Yes
Inclusion criteria
* Individuals who… * …are free-living, who fully understand and agree to the objectives of the study, who gave, signed and dated informed consent, which includes compliance with the requirements and restrictions listed in the informed consent form and in this protocol. * …are 'healthy' men and current combined oral contraceptive (COC)-using women (having taken the COC for at least 3 months and should they be eligible and willing to participate, are happy to continue taking the same COC during the duration of their participation). * …are aged 18-35 years * …engage in \< 5 hours of vigorous exercise a week. This information will be obtained during the initial study brief and using the health screening questionnaire. * …have a habitual fluid consumption of ≤ 1.6 L/day OR ≥ 2.9 L/day for men and ≤ 1.5 L/day OR ≥ 2.5 L/day for women, verified by a 7-day fluid intake record. * …have a day-to-day variation in fluid intake of ≤ 25%. * …have a verified UOsm aligned with the following: * IF habitual low TFI, i.e., TFI ≤ 1.5 L/day for women OR ≤ 1.6 L/day for men have a UOsm ≥ 500 mOsm/kg. * IF habitual high TFI, i.e., TFI ≥ 2.5 L/day for women OR ≥ 2.9 L/day for men have a UOsm \< 500 mOsm/kg. * …have a day-to-day variation in UOsm ≤ 28%; UOsm screening will be determined during verification and intervention periods. * …have access to a domestic fridge at home so that urine samples can be stored prior to laboratory visits. * …have a body mass index (BMI) \< 30 kg/m². * …have an IOS or Android smart phone and therefore the ability to download the HidrateSpark mobile application.
Exclusion criteria
* Individuals who… * …are vulnerable, as defined by individuals whose willingness to volunteer in the study may be unduly influenced by the expectation, whether justified or not, of benefits associated with participation, or of a retaliatory response from senior members of a hierarchy in case of refusal to participate (for example, if members of a group with a hierarchical structure linked to the investigator or to the sponsor, subordinate laboratory personnel, and employees of the investigator or sponsor. * …are not able to answer questionnaires by writing whatever the reason. * …have a loss of personal liberty, by administrative or judicial decision. * …engage in \> 5 hours of vigorous exercise a week. * …engage in endurance exercise bouts lasting longer than 40 minutes. * …do not have access to a domestic fridge at home so that urine samples can be stored prior to laboratory visits. * …do not have an IOS or Android smart phone and therefore do not have the ability to download the HidrateSpark application. * …are currently participating in another relevant clinical study (e.g., likely to influence hydration status or stress responsivity). * …have completed the TSST before. * …are expected to be living in the same home as a current participant. Health screening Individuals who… * …have had any surgery or medical procedure requiring a general anaesthesia in the preceding 4 weeks, or who plan to have one during the study. * …have an ongoing clinically diagnosed medical condition. * …are currently taking prescribed medication for an ongoing medical condition. * …are clinically diagnosed with one of the following psychiatric disorders known to influence stress reactivity: melancholic or atypical depression; panic disorder; obsessive-compulsive disorder; schizophrenia; social or generalised anxiety disorder; autism spectrum disorder; post-traumatic stress disorder; psychosis. * …have a clinically diagnosed sleeping disorder. * …are a current smoker (including e-cigarettes and vapes). * …have had a respiratory or gastrointestinal infection within the last 2 weeks. * …have a clinically diagnosed eating disorder. * …have a special medicated diet (e.g., for obesity, anorexia, metabolic pathology). * …have changed their dietary habits within the last 4 weeks or plan to change their diet during the study (e.g., start of a high-fibre diet, intentionally reducing or increasing calorie intake). * …take dietary supplements known to influence stress reactivity (e.g., high-dose caffeine). * …are women not currently on COC (e.g., naturally menstruating, or on progestogen-only forms of contraception, such as IUS, mini-pill, implant or injection). * …are women currently using COC but for \< 3 months prior to reading the participant information sheet or not planning to continue taking COC during their potential participation in the study. * …are pregnant women or women planning to become pregnant during the study or are breast-feeding women. Total fluid intake screening Individuals who… * …have a daily total fluid intake of: * Men: between 1.6 and 2.9 L/day. * Women: between 1.5 and 2.5 L/day. * …have a day-to-day variation in fluid intake of \>25%. * …have a UOsm of: * Men: \< 500 mOsm/kg if habitual TFI is ≤ 1.6 L.day or ≥ 500 mOsm/kg if habitual TFI is ≥ 2.9 L/day. * Women: \< 500 mOsm/kg if habitual TFI is ≤ 1.5 L/day or ≥ 500 mOsm/kg if habitual TFI is ≥ 2.5 L/day. * …have a day-to-day variation in UOsm \> 28%. * …habitually consume \> 1.3 L/day of caffeinated hot beverages (e.g., tea, coffee; 1.3 L equates to 4 average sized mugs) as estimated by a fluid intake record questionnaire. * …consume ≥ 91 units of alcohol per month (equivalent to more than 3 pints of beer per day or more than 3 large glasses of red wine per day).
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Salivary cortisol reactivity to acute psychosocial stress | Assessed during the main trial (day 8 of the intervention period). Saliva samples will be taken pre (-30 and -5 minutes) and post (+0, +10, +20, +30, +45 and +60 minutes) stress test. | Changes in the concentration of salivary free cortisol throughout the psychosocial stress test. Cortisol will be measured in stimulated saliva samples and analysed by ELISA. Delta changes (increase/decrease) in cortisol response will also be calculated. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Plasma copeptin | Copeptin will be assessed using a single blood sample taken on the morning of the main trial (day 8 of intervention period). | Plasma copeptin will be analysed by ELISA and compared cross-sectionally between intervention conditions. |
| Urine osmolality (UOsm) | Late-afternoon urine samples will be collected on days 6 and 7 of the verification and intervention periods. Spot urine samples will be collected on the morning and afternoon visits of the main trial (day 8 of the intervention period). | The concentration of osmotic solutes present in the urine, measured using a freezing point depression osmometer. |
| Urine colour | Late-afternoon urine samples will be collected on days 6 and 7 of the verification and intervention periods. Spot urine samples will be collected on the morning and afternoon visits of the main trial (day 8 of the intervention period). | Urine colour, a common marker used for assessing hydration status, will be assessed using a urine colour chart that has been developed to assess urine concentration in healthy humans. |
| Plasma osmolality | A venous blood sample will be taken on the morning of the main trial (day 8 of the intervention period). | A marker of intracellular osmolality, measured using a freezing point depression osmometer. Plasma will be derived from venous blood. |
| Sleep duration | Verification period: an actigraph will be worn continuously from day 5 until the end of the verification period. Intervention period: an actigraph will be worn continuously from day 5 until the stress test on day 8. | Total sleep time (minutes) will be measured using accelerometery-based movement data recorded using a wrist-worn actigraph. |
| Sleep efficiency | Verification period: an actigraph will be worn continuously from day 5 until the end of the verification period. Intervention period: an actigraph will be worn continuously from day 5 until the stress test on day 8. | Sleep efficiency will be calculated using the following equation: (total sleep time/total time in bed) \* 100. |
Countries
United Kingdom
Contacts
CONTACTWilliam J Searle, PhD
CONTACTHarry K W Bell, MSc
PRINCIPAL_INVESTIGATORNeil P Walsh, PhD
Liverpool John Moores University
Outcome results
None listed