The effect of drinking tea at high altitude on hydration status and mood

Abstract

The effect of drinking tea on hydration status and mood was studied in nine male and four female members of expeditions based at Mt. Everest base camp at an altitude of 5,345 m. Whilst exposed to altitude-cold diuresis, participants were subjected to a crossover experimental design comprising two 24-h dietary interventions. In the "tea" condition, hot brewed tea formed a major part of fluid intake, whereas in the "no-tea" condition tea was excluded from the diet. Subjects were prohibited in both cases from consuming other caffeinated beverages, caffeinated foods, and alcoholic drinks. Mean fluids ingested [mean (SE); tea=3,193 (259) ml versus no tea=3,108 (269) ml] and urine volume (tea=2,686 (276) ml versus no tea=2,625 (342) ml] were similar under both conditions. Statistical analysis found no difference in urine stimulated as a result of the tea intervention (P=0.81). Several markers of hydration status were also taken immediately pre and post each condition, including measures of urine specific gravity, urine electrolyte balance (K+, Na+), and urine colour. None of these measures indicated a difference in hydration status as a result of the dietary intervention in either the control or tea condition. A difference was, however, found in mood, with subjects reporting reduced fatigue when tea was included in the diet (P=0.005). The study shows therefore that even when drunk at high altitude where fluid balance is stressed, there is no evidence that tea acts as a diuretic when consumed through natural routes of ingestion by regular tea drinkers, but that it does have a positive effect on mood.

Black tea – helpful or harmful? A review of the evidence

“…This position was confirmed by a study (Scott et al, 2004) that compared regular tea consumers with non-consumers in a crossover study of fluid balance during extreme physiological stress. Participants were members of an expedition at Mount Everest Base Camp.…”

“…Evidence that tea had no diuretic effect unless the caffeine content of tea consumed at one sitting exceeded 300 mg. Maughan and Griffin (2001) No evidence that tea was dehydrating at altitude. Scott et al (2004). Dental health Little evidence to support effect of tea on plaque inhibition.…”

Behavioural effects of compounds co-consumed in dietary forms of caffeinated plants

“…However, sedation ratings were decreased by caffeine irrespective of vehicle, representing a failure to replicate earlier findings (128) . In a naturalistic study at high altitude, Scott et al (129) demonstrated that tea drinking was associated with lower fatigue ratings in regular tea drinkers. More recently De Bruin et al (130) described two randomised, controlled trials of black tea as compared with placebo tea.…”

An Investigation into Equations for Estimating Water Requirements and the Development of New Equations for Predicting Total Water Intake

“…Examples include measuring urine specific gravity or urine osmolality (Grandjean et al, 2003;Manz & Wentz, 2005;Martin et al, 2006;Popowski et al, 2001;Scott, Rycroft, Aspen, Chapman, & Brown, 2004;Wakefield et al, 2002), urine volume (Grandjean et al, 2003;Scott et al, 2004;Shirreffs et al, 2004), or urine color (Armstrong, 1994;Fletcher, Slaymaker, Bodenham & Vucevic, 1999;Mentes, Wakefield, & Culp, 2006;Scott et al, 2004;Wakefield et al, 2002). There are gender and race/ethnicity differences in some urinary indices (e.g.…”

“…Yet, evidence which supports the contribution of caffeinated and alcoholic beverages towards hydration and as a source of water has been provided in the literature (Grandjean et al, 2000;Kant, Graubard, & Atchison, 2009;Scott et al, 2004;Vivanti et al, 2010). Grandjean et al (2000) reported no change in hydration status when the TWI including caffeinated beverage intake from habitual caffeine consumers was compared to TWI from non-caffeine consumers.…”