HydrationHydration scientific library volume 2 http://www.europeanhydrationinstitute.org/ scientific library volume 2

1.
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?

2. 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 adults
A review by Ronald J. Maughan - Chairman of the Science Advisory Board
www.europeanhydrationinstitute.org
HYDRATION SCIENTIFIC LIBRARY
3. EHI Update: March 2011

3. A recent study has investigated
relationships between the types and
volumesofdifferentdrinksconsumed
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 show
that a higher total fluid
consumption was not
associated with either
IHD mortality or stroke
mortality in men
or women.
TYPE OF DRINK, ISCHAEMIC HEART
DISEASE AND STROKE
Dr. Susan Shirreffs
www.europeanhydrationinstitute.org
HYDRATION SCIENTIFIC LIBRARY
3. EHI Update: June 2011

4. 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
www.europeanhydrationinstitute.org
HYDRATION SCIENTIFIC LIBRARY
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”

5. 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
www.europeanhydrationinstitute.org
HYDRATION SCIENTIFIC LIBRARY
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.

6.
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