Investigating the Influence of Fluid Intake on Saliva Cortisol: Diurnal Variation and Acute Response to Psychological Stress in Young Adults
Overview
- Phase
- Not Applicable
- Intervention
- Not specified
- Conditions
- Healthy
- Sponsor
- Liverpool John Moores University
- Enrollment
- 71
- Locations
- 1
- Primary Endpoint
- Cortisol awakening response (CAR)
- Status
- Completed
- Last Updated
- last year
Overview
Brief Summary
Chronic low water intake may raise the risk of morbidity and mortality by influencing key water regulating hormones (e.g., AVP), which are known to modulate glucoregulation and renal function. For example, AVP stimulates the HPA axis to release the glucocorticoid stress hormone cortisol with potentially far-reaching effects on metabolism, immunity and inflammation. One study observed elevated blood cortisol in a group of low water drinkers, albeit cortisol was measured at one time of day only. However, in the field of psychobiology, researchers have traditionally related more dynamic assessments of cortisol with health outcomes; by evoking cortisol responses to acute standardised laboratory stressors, such as The Trier social stress test. More recently, researchers have appreciated the importance of circadian variability in cortisol levels, by examining influences on, and consequences of individual differences in the diurnal variation of cortisol. The major measurable parameters of the diurnal variation are; the cortisol awakening response (CAR), which is the rise in cortisol during the first 30-45 minutes following awakening, and the diurnal cortisol slope, which is the rate of decline in cortisol levels across the day, from morning to evening. These parameters are considered to reflect different aspects of HPA axis function; with the CAR best reflecting the adrenal capacity to respond to stress and awakening and diurnal slope more indicative of daily cortisol exposure. Although distinct, both blunted CAR and a flattened diurnal cortisol slope appear to be consistent markers of HPA axis dysfunction and related to a variety of poor health outcomes. Therefore, it has been recommended that contemporary research should simultaneously estimate an individual's awakening cortisol responsiveness, and diurnal slope, thereby capturing distinct and important components of HPA axis function. The shared pathways that regulate body water, diurnal variation in cortisol and our response to stress underpin the broad aim of this research programme: to investigate the influence of low and high fluid intake on diurnal cortisol variation and the cortisol response to acute stress.
The aims of this study are to investigate:
- The influence of a change in water intake behaviour on diurnal saliva cortisol variation as assessed by the CAR (primary outcome)
- The influence of a change in water intake behaviour on biomarkers of hydration and thirst as assessed by urine osmolality, urine colour and thirst sensation.
- The influence of habitual low and high total fluid intake on saliva cortisol response to an acute psychological stress (secondary outcome)
- Investigate the influence of a change in water intake behaviour on plasma biomarkers of hydration as assessed by plasma osmolality and plasma copeptin (exploratory outcome)
Investigators
Eligibility Criteria
Inclusion Criteria
- •Participants who...
- •are free-living, who fully understands 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 (ICF) and in this protocol
- •have read and signed the study informed consent.
- •are overtly healthy men and current COC using women (taking COC for at least 3-months and should they be eligible and willing to participate, are happy to continue taking COC during their study participation) aged 18-35 years who engage in \<5 hours of physical activity per week (in accordance with previously defined classifications). 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 7-day fluid intake record.
- •have a verified UOsm aligned with the following and ≤ 28% day-to-day differences in UOsm; this will be determined during the TFI screening week and familiarisation visit 1: 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 OR 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 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/m
- •have an IOS or Android smart phone and therefore the ability to download the HidrateSpark and MyFitnessPal mobile applications.
Exclusion Criteria
- •Participants who...
- •had any surgery or intervention requiring a general anaesthesia in the preceding 4 weeks, or who plans to have one during the study.
- •have a history of chronic metabolic or gastrointestinal disease, or gastrointestinal surgery except for appendectomy.
- •has chronic or iatrogenic immunodeficiency (e.g., Chemotherapy, HIV).
- •present a severe evolutive or chronic pathology (e.g., cancer, tuberculosis, Crohn's disease, cirrhosis, multiple sclerosis, Type I diabetes...).
- •have cardiac, respiratory (including asthma) or renal insufficiency, cardiomyopathy, valvopathy and medical history of rheumatic fever.
- •are receiving (currently or in the 4 last weeks) systemic treatment or topical treatment likely to interfere with the study parameters; specifically, relating to the stress response (e.g., steroid treatment may influence cortisol response) and hydration regulation (e.g., diuretics). Other excluded medications include antibiotics, intestinal or respiratory antiseptics, anti-rheumatics, antiphlogistics (except aspirin or equivalent at doses preventing from aggregation of platelets or blood clotting), anti-inflammatory and steroids prescribed in chronic inflammatory diseases.
- •are taking any treatment for anorexia, weight loss, or any form of treatment likely to interfere with metabolism or dietary habits (e.g., diuretic, hypolipemic, hypoglycemic treatments).
- •have a clinically diagnosed psychiatric disorder.
- •have a clinically diagnosed sleeping disorder.
Outcomes
Primary Outcomes
Cortisol awakening response (CAR)
Time Frame: Assessed during the first 45 minutes after awakening
A biomarker for Hypothalamic Pituitary Adrenal activity; a naturally occurring increase in cortisol upon waking, assessed by ELISA
Secondary Outcomes
- Thirst sensation(hirst sensation will be collected for daily for a total of 15 days across the habitual and intervention periods.)
- Urine Osmolality(Mid-afternoon urine samples will be collected on days 2, 5, 6 and 7 during the habitual and on days 10, 13 and 14 of the intervention periods. T)
- Change in saliva cortisol to acute psychological stress(Delta changes (increase/ decrease) in cortisol response (calculated by subtracting the baseline cortisol value from the peak post-stress induction level (-30 minutes pre-stress minus 10 minutes post-stress))
- Urine colour(Mid-afternoon urine samples will be collected on days 2, 5, 6 and 7 during the habitual and on days 10, 13 and 14 of the intervention periods. T)