hydration scientific library volume 2

Hydration Scientific Library (Volume 2)

Index

• Water turnover in children and young adults.

• Type of drink, ischaemic heart disease and stroke.

• Beverages containing glucose and caffeine help to maintain mental performance and improve mood under stressful conditions.

• Are caffeinated beverages less hydrating than pure water?.

The recent scientific opinion on water from the European Food Safety Authority (EFSA) concluded “that adequate intakes of water for children can be derived from observed intakes, corrected for a desirable water-energy relationship and corrected for inter-individual variation, particularly from those studies in which the water contribution by food has been or can be assessed” (http://www.efsa.europa.eu/en/scdocs/doc/1827.pdf).

Their suggested adequate intakes were 1,600 mL/day for boys and girls 4 to 8 years of age; 2,100 mL/day for boys 9 to 13 years of age; 1,900 mL for girls 9 to 13 years of age. Adolescents of 14 years and older were considered as adults with respect to adequate water intake and the adult values apply. Adequate total water intakes for females were identified to be 2.0 L/day and for males 2.5 L/day. These reference values for total water intake included water from drinking water, beverages of all kind, and from food moisture, but it must be recognised

that observational data based on assessments of water intake and loss are prone to large errors due to difficulties in assessing all sources of intake and loss.

The use of isotopically labelled water, however, can provide objective data on water turnover: if total body water is stable over the measurement period, intake must equal the measured loss. Rush et al measured water turnover using deuterated water in 91 healthy children (40 boys, 51 girls; age 5-14 years) and 109 healthy young adults (80 women, 29 men; age 18-27 years) with a wide range of body mass index (13.3-51.8 kg/m2) and percent body fat (6-59%). All lived in a temperate climate (Auckland, New Zealand). Total energy expenditure (TEE) and resting metabolic rate were measured by the doubly labelled water technique and indirect calorimetry, respectively. Mean (SD) water turnover was 1.77±0.57, 1.79±0.44, 2.85±0.82, and 3.90 ±0.81 L/day in girls, boys, women and men, respectively. Water turnover

indexed to body surface area did not differ significantly between girls and women but was higher in men than boys. Water turnover indexed to TEE was 0.8 mL/kcal in girls and boys and 1.0 mL/kcal in women and men. This study provides objective data on water turnover for children and young adults shows that anthropometric parameters can account for the variation between girls, boys and women but not between these groups and the more active men. Comparison of group mean intakes with the EFSA adequate intakes may not be helpful with accounting for variables such as body size, body composition and activity level.Rush EC, Chhichhia P, Kilding AE, Plank LD. Water turnover in children and young adults. Eur J Appl Physiol 2010; 110(6): 1209-14

WATER TURNOVER IN CHILDREN AND YOUNG ADULTSA review by Ronald J. Maughan - Chairman of the Science Advisory Board

www.europeanhydrationinstitute.org

HYDRATION SCIENTIFIC LIBRARY

3. EHI Update: March 2011

A recent study has investigated relationships between the types and volumes of different drinks consumed and mortality due to ischaemic heart disease (IHD) and stroke. The study was undertaken because chronic mild dehydration has been associated with fatal IHD and stroke and it has been suggested that total fluid intake is inversely associated with IHD or stroke mortality. The relationships were investigated from data initially collected from 120,852 subjects aged 55-69 years in 1986. Mortality data were then collected over a 10-year follow-up period. A total of 1789 IHD mortality cases and 708 stroke mortality cases occurred during the follow-up.

The mean daily total fluid consumption from beverages was 1462 ml/d in the males and 1341 ml/d in the females. The major beverages consumed by the males and females were coffee (mean 581 and 498 ml/d, respectively), tea (mean 319 and 384 ml/d, respectively) and milk (mean 187 and 181 ml/d, respectively). Only a very little amount of the daily total fluid intake was in the form of water consumption (mean 82 ml/d

in men and 109 ml/d in women). The results shows that a higher total fluid consumption was not associated with either IHD mortality or stroke mortality in men or women. But when analysing specific beverages, a positive association between coffee consumption and IHD mortality was observed in men (hazard ratio (HR) 1.09, 95% CI 1.00, 1.18), while an inverse relationship was observed in women (HR: 0.88, 95% CI 0.78, 1.00). For tea consumption, an inverse relationship with IHD mortality was observed in men (HR: 0.91, 95% CI 0.83, 1.00). No association with water intake was observed.

The authors concluded that total fluid intake was not associated with IHD or stroke mortality in either men or women. Coffee consumption was inversely associated with IHD mortality in women only, while a higher tea intake was associated with lower IHD mortality in men only.

Refererences:Leurs LJ, Schouten LJ, Goldbohm RA, van den Branft PA. (2010) Total fluid and specific beverage intake and mortality due to IHD and stroke in the Netherlands Cohort Study. British Journal of Nutrition, 104(8), 1212-1221.

Dr. Susan Shirreffs completed her first degree in Physiology at Aberdeen University in 1993, followed by a PhD in Exercise Physiology in the area of Post-exercise re-hydration. After completing a post-doc and lecturing for 5 years at Aberdeen University - during which time she also spent some time working at the Copenhagen Muscle Research Institute – Dr. Shirreffs moved to the School of Sport, Exercise and Health Sciences at Loughborough University, England, where she now holds the position of Reader.

The results showthat a higher total fluid consumption was not associated with either IHD mortality or stroke mortality in menor women.

TYPE OF DRINK, ISCHAEMIC HEART DISEASE AND STROKEDr. Susan Shirreffs



3. EHI Update: June 2011

acute stress has been linked to changes in cognitive performance and mood, and these have in some way been associated to an increased release of cortisol due to stress. both glucose and caffeine consumed in isolation have been shown to regulate cortisol response and affect cognitive performance and affect mood. nonetheless, there has been very little research regarding their behavioural and physiological effects when taken together. The aim of this review was to assess the effect of the two substances in combination under stressful and physically demanding conditions (such as fire-fighting training) on cognition, mood and cortisol release and to investigate the neural basis of these effects.

sünram-lea et al (1) using a double-blind design, administered a 330-ml drink to 81 participants. drinks contained either (a) 50 g glucose and 40 mg caffeine, (b) 10.25 g of fructose/ glucose and 80 mg caffeine or a placebo drink, and were tested across a range of cognitive tasks, mood and physiological measures. The results demonstrated an increase in grip strength and improved memory performance after consuming the drink containing 50 g glucose and 40 mg caffeine, and both active drinks resulted in improved outcomes on the information processing task compared to the placebo. In regards to the effect on mood, the drink containing 50 g glucose and 40 mg caffeine reduced anxiety levels and significantly decreased self-reported levels of stress following the fire-fighter training. serra-grabulosa et al (2) previously evaluated the effects of caffeine

and glucose on sustained attention, using functional magnetic resonance imaging (fMrI) in a double-blind, randomized trial with 40 young right-handed healthy, low caffeine-consuming subjects. participants who received combined caffeine and glucose showed similar performance to the others but had enhanced activation in the bilateral parietal and left prefrontal cortex, both areas being related to processes affecting sustained attention and working memory.

based on the results of both studies, in situations where stress is combined with physical performance, consumption of a drink containing glucose and caffeine may provide an easy to implement and cost effective option for maintaining mental performance levels, especially sustained attention and working memory processes, as well as ameliorating the negative effects of stress on mood.

refererences:1. sünram-lea sI, owen-lynch J, robinson sJ, Jones e, hu h. The effect of energy drinks on cortisol levels, cognition and mood during a fire-fighting exercise. psychopharmacology (berl). 2011 Jun 28. [epub ahead of print] pubMed pMId: 21710168.

2. serra-grabulosa JM, adan a, falcón c, bargalló n. glucose and caffeine effects on sustained attention: an exploratory fMrI study. hum psychopharmacol. 2010 nov;25(7-8):543-52.

beverages conTaInIng glucose and caffeIne help To MaInTaIn MenTal perforMance and IMprove Mood under sTressful condITIons a review by professor lluís serra-Majem



3. EHI Update: September 2011

Both glucose and caffeine consumed in isolation have been shown to regulate cortisol response and affect cognitive performance and mood. Nonetheless, there has been very little research regarding their behavioural and physiological effects when taken together”

Some.authors.believe. that.caffeinated.beverages.might.have. lower. hydrating. effects. compared. to. water.. This.difference. might. be. due. to. the. direct. diuretic. effect. of.caffeine,. which. would. negatively. compensate. for. the.hydrating. action. of. the. water. medium. in. which. it. is.dissolved.

In.truth,.the.diuretic.effect.of.caffeine.only.takes.place.at.high.(400-600.mg/d).doses.and.is.modest.in.magnitude..However,.based.on.this.contention,.the.hydrating.effects.of. caffeinated. beverages. such. as. tea,. coffee,. and. cola-based.products.have.been.questioned.

To.shed.light.on.this.issue,.a.recent.controlled.study.from.the.UK.has.investigated,.in.a.cross-over.protocol,.whether.identical.volumes.of.water.or.black.tea.exert.identical.or.different.hydrating.effects.in.healthy.volunteers.

The.authors.enrolled.21.healthy.male.adults,.19.of.whom.completed.the.protocol..Subjects.were.given.either.4.or.6.cups.of.tea.(prepared.in.a.standard.way.and.containing.40.mg.of.caffeine/cup).or.hot.water.(again,.4.or.6.cups).over.a. 12-hour. period.. Food. consumption. was. standardized.and. physical. activity. reduced. to. a. minimum.. The. total.amount.of.caffeine.consumed.by.the.volunteers.was.160.mg.per.day.in.the.4-cups.intervention.and.240.mg.per.day.during.the.6-cups.phase.

At. regular. intervals,. blood. was. drawn. and. a. white. cell.count,. osmolality,. electrolytes,. creatinine,. and. other.metabolites. were. determined.. In. addition,. the. total. 24-hour.urine.volume.and.urinary.osmolality.were.assessed.

This. study. did. not. report. any. difference. among. the.measured. parameters. after. the. consumption. of. either.water. of. black. tea.. In. particular,. 24-h. urinary. volumes.were. very. similar. after. the. consumption. of. 4. cups. of.tea.or.water.(1,117.vs.1,228.mL,.respectively).or.after.6.cups. of. tea. or. water. (1,498. vs. 1,458. mL,. respectively)..Creatininuria.and.renal.excretion.of.Na+.and.K+.were.also.very.similar.in.the.two.groups.

The. conclusion. of. this. study. is. that. caffeine. –. at. the.tested. doses. (higher. than. those. habitually. ingested. in.great. Britain). -. does. not. exert. any. significant. effects.on. the. studied. parameters.. Therefore,. the. contribution.to. hydration. of. the. caffeinated. beverages. studied. is.comparable.to.that.of.water..This.piece.of.information.is.useful.to.those.who.use.caffeinated.beverages.as.thirst-quenchers.

Refererence:

Carrie. H.. Ruxton. and. valerie. A.. Hart:. Black. tea. is. not. significantly.different.from.water.in.the.maintenance.of.normal.hydration.in.human.subjects:.results.from.a.randomised.controlled.trial

British.Journal.of.Nutrition.(2011),.106,.588–595.

ARE.CAFFEINATED.BEvERAgES.LESS.HYDRATINg.THAN.PURE.WATER?A.review.by.Prof..Andrea.Poli



3. EHI Update: December 2011

In truth, the diuretic effect of caffeine only takes place at high (400-600 mg/d) doses and is modest in magnitude.

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hydration scientific library volume 2

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