The Influence of Fluid Intake on Mental Performance

NCT07789847 | Recruiting

• 1 other identifier: Everyday Hydration Study 1
• Study Type: interventional
• Target: 192
• Locations: 1 country
• Sites: 1

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.

Conditions

Hydration Status; Psychosocial Stress; Fluid Intake

Outcome Measures

Primary Outcomes (1)

• Salivary cortisol reactivity to acute psychosocial stress

  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.

  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.

Secondary Outcomes (6)

• Plasma copeptin

  Copeptin will be assessed using a single blood sample taken on the morning of the main trial (day 8 of intervention period).

• 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).

• 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).

• Plasma osmolality

  A venous blood sample will be taken on the morning of the main trial (day 8 of the intervention period).

• 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.

Other Outcomes (14)

• State anxiety (STAI-S) response to acute psychosocial stress

  Assed during the main trial (day 8 of the intervention period). The STAI-S will be administered pre (-30 and -5 minutes) and post (+0, +10, +20, +30, +45 and +60 minutes) stress test.

• Subjective stress response to acute psychosocial stress

  Assessed during the main trial (day 8 of the intervention period). The Subjective Stress Scale will be administered pre (-30 and -5 minutes) and post (+0, +10, +20, +30, +45 and +60 minutes) post stress test.

• Trait anxiety (STAI-T) profiling

  The STAI-T will be administered once, immediately after enrolling.

Study Arms (2)

Verification period

NO INTERVENTION

7 consecutive days where participants will drink fluids as they do normally do.

Intervention period

EXPERIMENTAL

7 consecutive days where the participants will be randomly assigned to either the habitual or intervention condition. * Habitual: maintain their usual daily total fluid intake. * Intervention: habitual low daily TFI will be prescribed a total fluid intake of 3.5 L/day for men and 3.3 L/day for women. Habitual high daily total fluid intake will be prescribed a total fluid intake of 1.3 L/day for both men and women. On day 8, participants will perform a psychosocial stress test. Participants will be instructed to maintain their usual intake of other beverages i.e., tea/coffee to achieve their target total fluid intake.

Behavioral: Modifying daily total fluid intake

Interventions

Modifying daily total fluid intake BEHAVIORAL

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.

Intervention period

Eligibility Criteria

• Age: 18 Years - 35 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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.

You may not qualify if:

• 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.

Sponsors & Collaborators

• Liverpool John Moores University: lead
• Unilever R&D: collaborator

Study Sites (1)

Liverpool John Moores University

Liverpool, United Kingdom

RECRUITING

Related Publications (14)

• Lazzarino AI, Hamer M, Gaze D, Collinson P, Steptoe A. The association between cortisol response to mental stress and high-sensitivity cardiac troponin T plasma concentration in healthy adults. J Am Coll Cardiol. 2013 Oct 29;62(18):1694-1701. doi: 10.1016/j.jacc.2013.05.070. Epub 2013 Jun 27.

  PMID: 23810896 BACKGROUND

• Turner AI, Smyth N, Hall SJ, Torres SJ, Hussein M, Jayasinghe SU, Ball K, Clow AJ. Psychological stress reactivity and future health and disease outcomes: A systematic review of prospective evidence. Psychoneuroendocrinology. 2020 Apr;114:104599. doi: 10.1016/j.psyneuen.2020.104599. Epub 2020 Feb 1.

  PMID: 32045797 BACKGROUND

• Dhabhar FS. Effects of stress on immune function: the good, the bad, and the beautiful. Immunol Res. 2014 May;58(2-3):193-210. doi: 10.1007/s12026-014-8517-0.

  PMID: 24798553 BACKGROUND

• Gibbs DM. Vasopressin and oxytocin: hypothalamic modulators of the stress response: a review. Psychoneuroendocrinology. 1986;11(2):131-9. doi: 10.1016/0306-4530(86)90048-x.

  PMID: 3018820 BACKGROUND

• Roussel R, El Boustany R, Bouby N, Potier L, Fumeron F, Mohammedi K, Balkau B, Tichet J, Bankir L, Marre M, Velho G. Plasma Copeptin, AVP Gene Variants, and Incidence of Type 2 Diabetes in a Cohort From the Community. J Clin Endocrinol Metab. 2016 Jun;101(6):2432-9. doi: 10.1210/jc.2016-1113. Epub 2016 Apr 6.

  PMID: 27049477 BACKGROUND

• Enhorning S, Struck J, Wirfalt E, Hedblad B, Morgenthaler NG, Melander O. Plasma copeptin, a unifying factor behind the metabolic syndrome. J Clin Endocrinol Metab. 2011 Jul;96(7):E1065-72. doi: 10.1210/jc.2010-2981. Epub 2011 Apr 13.

  PMID: 21490073 BACKGROUND

• Boertien WE, Riphagen IJ, Drion I, Alkhalaf A, Bakker SJ, Groenier KH, Struck J, de Jong PE, Bilo HJ, Kleefstra N, Gansevoort RT. Copeptin, a surrogate marker for arginine vasopressin, is associated with declining glomerular filtration in patients with diabetes mellitus (ZODIAC-33). Diabetologia. 2013 Aug;56(8):1680-8. doi: 10.1007/s00125-013-2922-0. Epub 2013 Apr 28.

  PMID: 23624546 BACKGROUND

• Roussel R, Fezeu L, Bouby N, Balkau B, Lantieri O, Alhenc-Gelas F, Marre M, Bankir L; D.E.S.I.R. Study Group. Low water intake and risk for new-onset hyperglycemia. Diabetes Care. 2011 Dec;34(12):2551-4. doi: 10.2337/dc11-0652. Epub 2011 Oct 12.

  PMID: 21994426 BACKGROUND

• Chan J, Knutsen SF, Blix GG, Lee JW, Fraser GE. Water, other fluids, and fatal coronary heart disease: the Adventist Health Study. Am J Epidemiol. 2002 May 1;155(9):827-33. doi: 10.1093/aje/155.9.827.

  PMID: 11978586 BACKGROUND

• Allen MD, Springer DA, Burg MB, Boehm M, Dmitrieva NI. Suboptimal hydration remodels metabolism, promotes degenerative diseases, and shortens life. JCI Insight. 2019 Sep 5;4(17):e130949. doi: 10.1172/jci.insight.130949.

  PMID: 31484829 BACKGROUND

• Sontrop JM, Dixon SN, Garg AX, Buendia-Jimenez I, Dohein O, Huang SH, Clark WF. Association between water intake, chronic kidney disease, and cardiovascular disease: a cross-sectional analysis of NHANES data. Am J Nephrol. 2013;37(5):434-42. doi: 10.1159/000350377. Epub 2013 Apr 17.

  PMID: 23594828 BACKGROUND

• Clark WF, Sontrop JM, Macnab JJ, Suri RS, Moist L, Salvadori M, Garg AX. Urine volume and change in estimated GFR in a community-based cohort study. Clin J Am Soc Nephrol. 2011 Nov;6(11):2634-41. doi: 10.2215/CJN.01990211. Epub 2011 Sep 1.

  PMID: 21885793 BACKGROUND

• Ferreira-Pego C, Guelinckx I, Moreno LA, Kavouras SA, Gandy J, Martinez H, Bardosono S, Abdollahi M, Nasseri E, Jarosz A, Babio N, Salas-Salvado J. Total fluid intake and its determinants: cross-sectional surveys among adults in 13 countries worldwide. Eur J Nutr. 2015 Jun;54 Suppl 2(Suppl 2):35-43. doi: 10.1007/s00394-015-0943-9. Epub 2015 Jun 12.

  PMID: 26066354 BACKGROUND

• Kashi DS, Hunter M, Edwards JP, Zemdegs J, Lourenco J, Mille AC, Perrier ET, Dolci A, Walsh NP. Habitual fluid intake and hydration status influence cortisol reactivity to acute psychosocial stress. J Appl Physiol (1985). 2025 Sep 1;139(3):698-708. doi: 10.1152/japplphysiol.00408.2025. Epub 2025 Aug 13.

  PMID: 40803748 BACKGROUND

Study Officials

• Neil P Walsh, PhD

  Liverpool John Moores University

  PRINCIPAL INVESTIGATOR

Central Study Contacts

William J Searle, PhD

CONTACT

01519041031; w.j.searle@ljmu.ac.uk

Harry K W Bell, MSc

CONTACT

h.k.bell@ljmu.ac.uk

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: BASIC SCIENCE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: 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.

Study Record Dates

• First Submitted: July 17, 2026
• First Posted: August 27, 2026
• Study Start: June 22, 2026
• Primary Completion (Estimated): September 1, 2027
• Study Completion (Estimated): December 1, 2027
• Last Updated: August 27, 2026

Record last verified: 2026-06

Data Sharing

• IPD Sharing: Will share
• Time Frame: Beginning 3 months after publication with no end date.

Locations

GB (1)