Hydration scientific library volume 2

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

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Hydration scientific library volume 2

  1. 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. 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. 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. 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. 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. 6.             http://www.europeanhydrationinstitute.org/    

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