Emerging Hydration Science
In this section, you can access commentaries and analysis of selected scientific literature that is of particular relevance to healthy hydration.
Articles included in this section contain a brief overview, a summary of key findings and perspectives from the authors on how this research/study adds to the current knowledge base on healthy hydration. Where possible an electronic PDF version of the paper is also available for download.
Armstrong et al, 2012 and Ganio et al, 2011 – Mild dehydration affects mood in healthy young women and Mild dehydration impairs cognitive performance and mood of men
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Summary provided by Harris R. Lieberman, Ph.D ,Westwood, MA, USA and Prof. Lawrence E. Armstrong, University of Connecticut, Human Performance Laboratory, Storrs, CT, USA |
FULL ARTICLE (Ganio) – FREE with H4HI membership
FULL ARTICLE (Armstrong) – FREE with H4HI membership
Ganio, M.S., Armstrong, L.E., Casa, D.J., McDermott, B.P., Lee, E.C., Yamamoto, L.M., Marzano, S., Lopez, R.M., Jimenez, L., Le Bellego, L., Chevillotte, E., and Lieberman, H.R. (2011) Mild dehydration impairs cognitive performance and mood of men. British Journal of Nutrition 106(10),1535-1543, 2011.
Armstrong, L.E., Ganio, M.S., Casa, D.J., Lee, E.C., McDermott, B.P., Klau, J.F., Jimenez, L., Le Bellego, L., Chevillotte, E., Lieberman, H.R. Mild dehydration affects mood in healthy young women. Journal of Nutrition, vol. 142 no. 2, 382-388, February 1, 2012.
Introduction
It is well known that ensuring an adequate level of hydration plays an important role in overall health, including maintaining brain function. Scientific research on dehydration induced by high heat and exercise has shown that mental function (cognition) is greatly affected by severe dehydration.
Recently two large, carefully designed studies were conducted at the University of Connecticut, USA, to examine the effects of mild dehydration on cognitive function in healthy individuals. To measure mental function, tests of cognitive performance, mood and symptoms of dehydration were used by the scientists. One study was conducted with 26 men and another with 25 women. Both studies examined the effects of mild dehydration on cognitive function using identical procedures. Men and women all took part in two mildly dehydrated conditions and a fully hydrated condition which could be directly compared using standard statistical procedures. To assess the level of dehydration, body weight was measured using special, high accuracy scales. Men on average were 1.59% dehydrated, women were 1.36% dehydrated. Most adults reach this level of dehydration one or more times during the course of a week.
Key Findings
The results showed that, in both men and women, mild dehydration had an adverse effect on mood as well as ability to concentrate. When mildly dehydrated, both men and women were more likely to feel fatigued and to have diminished cognitive performance, specifically vigilance. Men were more likely to experience short-term memory degradation when mildly dehydrated, but overall, women were more sensitive to dehydration than men. For example, women were more likely to report a headache, fatigue, confusion and lack of energy. Women also felt moderate exercise was more difficult when dehydrated.
Relevance for healthy hydration
These studies provide a better understanding of the effects of mild dehydration on cognitive function of men and women and have many practical applications. They demonstrate the importance of maintaining optimal levels of hydration during normal daily activities and during moderate exercise. Both men and women will perform better and feel better if they maintain full hydration by regularly consuming water. In addition, vulnerable populations such as elderly people and children may be more susceptible to the adverse effects of dehydration on mood and cognitive performance.
Tang C, Zelenak C et al, 2011 – Hydration-sensitive gene expression in brain
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Summary provided by Prof. Florian Lang & Dr Cai Tang, Department of Physiology, Eberhard-Karls-University of Tübingen, Tubingen, Germany |
FULL PUBLISHED ARTICLE – FREE with H4HI membership
Rationale
Dehydration profoundly influences mental performance, neuroexcitability and possibly survival of neurons. The molecular neuronal mechanisms sensitive to dehydration remained, however, incompletely understood. The present study addressed the effect of water deprivation on gene expression in the brain. To this end, mice were exposed to a 24 hours deprivation of drinking water and neuronal gene expression was determined by microarray technology with subsequent confirmation by RT-PCR and partially Western blotting.
Key Findings
Water deprivation was followed by alterations of cerebral gene expression. Specifically dehydration upregulated the transcript levels of clathrin (light polypeptide Lcb), serum/glucocorticoid-regulated kinase (SGK) 1, and protein kinase A (PRKA) anchor protein 8-like. Water deprivation led to downregulation of janus kinase and microtubule interacting protein 1, neuronal PAS domain protein 4, thrombomodulin, purinergic receptor P2Y – G-protein coupled 13 gene, gap junction protein beta 1, neurotrophin 3, hyaluronan and proteoglycan link protein 1, G protein-coupled receptor 19, CD93 antigen, forkhead box P1, suppressor of cytokine signaling 3, apelin, immunity-related GTPase family M, serine (or cysteine) peptidase inhibitor clade B member 1a, serine (or cysteine) peptidase inhibitor clade H member 1, glutathion peroxidase 8 (putative), discs large (Drosophila) homolog-associated protein 1, zinc finger and BTB domain containing 3, and H2A histone family member V. In conclusion, water deprivation influences the transcription of a wide variety of genes in the brain, which may participate in the orchestration of brain responses to water deprivation.
Relevance for healthy hydration
The observations provide novel insight into the molecular consequences of inadequate hydration. They help to understand, how inadequate hydration could possibly affect mental performance, neuroexcitability and possibly survival of neurons. An influence on neuronal survival would have lasting effects on mental health. Future studies are required to bridge the molecular knowledge to the phenomenology of the interaction between hydration status and brain function.
Péronnet et al, 2011 – Pharmacokinetic analysis of absorption, distribution and disappearance of ingested water labeled with D2O in humans
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Summary provided by Prof. François Péronnet, Département de kinesiologie, Université de Montréal, Montréal, Quebec, Canada |
FULL PUBLISHED ARTICLE – FREE with H4HI membership
Péronnet F, Mignault D, du Souich P, Vergne S, Le Bellego L, Jimenez L, Rabasa-Lhoret R. European Journal of Applied Physiology, Published Ahead-of-print, October 2011.
This study describes the rate of absorption of water in the body water pool and the volume and rate of renewal of this pool. The experiment was conducted on 36 healthy male subjects (18-35 yo, 76.9 kg, BMI = 23.3 kg/m2) drinking ad libitum, with 2 L/day of natural mineral water in their beverages. Following ingestion of natural mineral water with deuterium oxide (D2O) as tracer, the deuterium to hydrogen ratio (D/H) was measured in blood over the following hour and in urine over the following 9 days.
Pharmacokinetic analysis of D/H show that water appeared in plasma and blood cells within 5 min following ingestion and was entirely distributed in the body water pool within ~75-120 min. The volume of the body water pool was 46.6 L (60.7 % body mass) and its turnover (or water clearance, i.e., the volume added in the pool from water in food and drinks and metabolic water, and removed from the pool through urine, feces, sweat, perspiration, and respiration, was 4.58 L/day. The mean residence time of water in the body water pool was 10.3 days indicating that half of the pool (i.e., the half-life) was replaced in 7.2 days.
Water ingested under the form of natural mineral waters, with a low mineral content, appears in plasma and blood cells in less than 5 min, and is distributed in the entire body water pool in less than 2 hours. In the young healthy male subjects studied who remained well hydrated by drinking 2 L of natural mineral water/day, the entire body water pool was completely renewed in ~50 days.
de La Guéronnière et al, 2011 – Increasing daily water intake decreases the kidney stone risk, measured by an indicator, the Crystallization Risk Index
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FULL PUBLISHED ARTICLE – FREE with H4HI membership
de La Guéronnière V, Le Bellego L, Jimenez IB, Dohein O, Tack I, Daudon M, Arch Ital Urol Androl. 2011;83(1):43-50.
Introduction
Kidney stones affect around 10% of the population and the incidence is increasing in many countries. Medical expenditures due to this condition are very high and rising concomitantly. In most cases, prevention of stone recurrence is based on dietary advice. It has been observed that a sufficient water intake, producing at least 2L/d urine, dilutes urine and lowers kidney stone formation risk. The purpose of this study therefore was to measure the effects of a daily additional 2L of water on a kidney stone risk indicator, called the crystallization risk index. Forty-eight volunteers were divided into two groups, control and treated. Following a baseline observation period, the “treated group” drank an additional 2L/d water load, while the “control group” had their usual fluid intake. Treated and control volunteers were compared at the end of the study.
Key Findings
The crystallization risk index significantly decreased in the treated group with the additional water intake, compared with the control group. The absolute daily additional water intake was actually 1.3 L/d in the treated group, because volunteers decreased their other usual fluid sources.
Relevance for health
This study demonstrates that increasing daily water intake to 1.3 L/d, and thus urinary volume, reduces the crystallization risk index and thus kidney stone risk.
Kavouras et al, 2011 – Educational intervention on water intake improves hydration status and enhances exercise performance in athletic youth
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Summary provided by Stavros A Kavouras PhD - Assistant Professor, Acting Director, Laboratory of Nutrition & Clinical Dietetics, Harokopio University, Athens, Greece |
FULL PUBLISHED ARTICLE – FREE with H4HI membership
Kavouras SA, Arnaoutis G, Makrillos M, Garagouni C, Nikolaou E, Chira O, Ellinikaki E, Sidossis LS. Scand J Med Sci Sports. 2011
Introduction
It has been well documented that a large percentage of both amateur and professional athletes start their training and/or competitions inadequately hydrated. Furthermore, even in optimal conditions with water and/or sports drinks availability, athletes of all ages tend to become dehydrated during exercise. Therefore, the purpose of our study was to investigate the effect of a nutrition intervention program, emphasising water consumption on the prevention of dehydration and exercise performance in young athletes. A total of 92 young trained volleyball and basketball athletes participating in a five day training camp were randomised to either the control (CON) or the intervention (INT) group.
Key Findings
More than 90% of the participants started the training camp inadequately hydrated. Only the INT group improved hydration status, resulting in enhanced running endurance performance, as a response to the intervention. No significant improvement in hydration or performance was found in the CON group.
Relevance for health
This study showed that a simple educational program, consisting of a lecture on hydration, use of the urine color chart, improved water availability, and body weighting before and after exercise in some practices, was effective in improving hydration. We also found that improving hydration status by ad libitum consumption of water can enhance performance in young athletes exercising in the heat. Similar educational programmes can be used to effectively improve hydration and performance in free living active youth.
