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No Evidence of Dehydration with Moderate Daily CoffeeIntake: A Counterbalanced Cross-Over Study in a Free-Living Population Sophie C. Killer¤, Andrew K. Blannin*, Asker E. Jeukendrup¤ School of Sport and Exercise Sciences, University of Birmingham, Birmingham, West Midlands, United Kingdom It is often suggested that coffee causes dehydration and its consumption should be avoided or significantly reduced tomaintain fluid balance. The aim of this study was to directly compare the effects of coffee consumption against wateringestion across a range of validated hydration assessment techniques. In a counterbalanced cross-over design, 50 malecoffee drinkers (habitually consuming 3–6 cups per day) participated in two trials, each lasting three consecutive days. Inaddition to controlled physical activity, food and fluid intake, participants consumed either 46200 mL of coffee containing4 mg/kg caffeine (C) or water (W). Total body water (TBW) was calculated pre- and post-trial via ingestion of DeuteriumOxide. Urinary and haematological hydration markers were recorded daily in addition to nude body mass measurement(BM). Plasma was analysed for caffeine to confirm compliance. There were no significant changes in TBW from beginning toend of either trial and no differences between trials (51.561.4 vs. 51.461.3 kg, for C and W, respectively). No differenceswere observed between trials across any haematological markers or in 24 h urine volume (24096660 vs. 24286669 mL, forC and W, respectively), USG, osmolality or creatinine. Mean urinary Na+ excretion was higher in C than W (p = 0.02). Nosignificant differences in BM were found between conditions, although a small progressive daily fall was observed withinboth trials (0.460.5 kg; p,0.05). Our data show that there were no significant differences across a wide range ofhaematological and urinary markers of hydration status between trials. These data suggest that coffee, when consumed inmoderation by caffeine habituated males provides similar hydrating qualities to water.Citation: Killer SC, Blannin AK, Jeukendrup AE (2014) No Evidence of Dehydration with Moderate Daily Coffee Intake: A Counterbalanced Cross-Over Study in aFree-Living Population. PLoS ONE 9(1): e84154. doi:10.1371/journal.pone.0084154 Editor: Dylan Thompson, University of Bath, United Kingdom Received August 14, 2013; Accepted November 12, 2013; Published January 9, 2014 Copyright: ß 2014 Killer et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permitsunrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: Funding for this study was provided by the Institute for Scientific Information on Coffee (ISIC). ISIC is a non-profit organisation, devoted to the studyand disclosure of science related to coffee and health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation ofthe manuscript.
Competing Interests: S.C. Killer and A.K. Blannin have declared that no competing interests exist. A.E. Jeukendrup is currently employed by PepsiCo Inc. and isan adjunct Professor at the University of Birmingham. The views expressed here are the views of the authors and not those of PepsiCo Inc. The currentemployment of Professor Asker Jeukendrup by PepsiCo Inc. does not alter the authors' adherences to all the PLOS ONE policies on sharing data and materials.
* E-mail: [email protected] ¤ Current address: School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, East Midlands, United Kingdom fractional sodium reabsorption in both the proximal tubule anddistal nephron. When consumed in large doses ($500 mg), Maintenance of fluid balance is essential to sustain human life.
caffeine elicits a diuretic effect [8–10]. The diuretic potential of Water intake balances fluid losses to achieve adequate hydration of caffeine in humans has been researched for many years, with the bodily tissues. Although there are widespread guidelines in first scientific report published over 80 y ago [11]. The authors of scientific literature and media for achieving optimal hydration these early findings suggested that whilst caffeine causes acute status and about the effects that various caffeinated beverages may diuresis, regular caffeine consumption may lead to a tolerance have on fluid balance, there is no clear consensus about how much developing against its diuretic effect. It has since been suggested fluid an individual should consume [1]. One study found total that caffeine withdrawal of as little as 4 days is sufficient for daily fluid intake observed in healthy adults varied from 0.416– tolerance to be lost [12]. Following the work of Eddy & Downs 4.316 L/day [2]. The current EFSA dietary references values for [11], there has been a range of studies that have investigated the water intakes for male adults is 2.5 L/day [3]. However, published effects of caffeine on hydration status (Table 1). These studies guidelines range from 1.5 L/day [4] to 3.7 L/day [5] for adult report observations across a range of caffeine forms and doses on males. It has been suggested that caffeinated beverages should not various markers of hydration status in either caffeine-habituated or be included in daily fluid requirement guidelines [6] and that a caffeine-naive populations (individuals who do not habitually glass of water should be consumed with every cup of coffee or tea consume caffeine, or those who have abstained from caffeine to ensure hydration is maintained [7].
consumption for $4 days). Although the data are somewhat Caffeine (1, 3, 7-trimethylxanthine) is a naturally occurring varied, the general trend is that higher doses of caffeine in caffeine- methylxanthine which can be found in coffee, tea and chocolate.
naive individuals will elicit an acute increase in urine volume, yet a Caffeine acts as an adenosine receptor antagonist to reduce PLOS ONE www.plosone.org January 2014 Volume 9 Issue 1 e84154 Coffee Ingestion and Fluid Balance Table 1. Effect of caffeine consumption on urine production.
Caffeine Dose (mg) 4 mg/d (200–700 mg) Habituated caffeine users Yes –during first dayonly 490–680 (8.7 mg/kg bw) Caffeine powder added to carbohydrate Caffeine naı¨ve (Habitual coffee electrolyte drink Vs carbohydrate drinkers – 4 day pre-trial deprivation) electrolyte drink Caffeinated coffee Caffeine naı¨ve (Habitual coffee drinkers – 5 day pre-trial deprivation) Habitual caffeine users – 98617 mg/day Habitual coffee drinkers – 8 h pre-trial deprivation Caffeine beverage Caffeine naı¨ve (Non-coffee drinkers – 3 week caffeine deprived) Caffeine naı¨ve (1 week caffeine deprived) Yes –during first houronly Caffeine beverage Caffeine habituated users Caffeine capsules Habitual caffeine users – 98617 mg/day Caffeine users – 12 h deprived Caffeinated carbonated cola, Caffeinated Caffeine habituated (61–464 mg/day) carbonated, non-caloric cola, Instant coffee low to moderate dose of caffeine does not induce a diuretic effect the caffeine or placebo group. The authors suggested that a moderate dose of caffeine does not alter TBW in healthy men. To Coffee is comprised of many bioactive compounds in addition date, no studies have investigated the effects of moderate coffee to caffeine. These active compounds may interact with each other consumption on TBW in caffeine-habituated adults using the and therefore coffee consumption cannot be directly compared to doubly labelled water dilution technique.
caffeine consumption in its purest form (1,3,7-trimethyl xanthine) It is estimated that 1.6 billion cups of coffee are consumed [18]. Interestingly, only two studies have specifically investigated worldwide every day [20], thus it is of interest to know whether the effects of caffeine in the form of coffee on hydration status.
coffee contributes to daily fluid requirement, or whether it causes One study investigated the effects of six cups of coffee (624 mg low-level chronic dehydration. In the present study, our aim was to caffeine) on urine excretion following a five day caffeine directly compare the effects of a moderate intake of coffee in deprivation period [10]. Over the 24 h period, authors report a caffeine-habituated adults against equal amounts of water across a 2.7% decrease in total body water and a 41% increase in urine wide range of hydration markers, including the gold standard excretion, with a subsequent 66% and 28% increase in urinary TBW measure.
sodium and potassium excretion, respectively. Due to the studydesign, which only included caffeine habituated participants who abstained from caffeine for 5 days prior to testing, the results of thestudy should be interpreted with caution before applying to habitual moderate-intake coffee drinkers. Another study investi- All participants were informed of the purposes of the study and gated the effects of consuming equal amounts of water, caffeinated the risks associated with the procedures. Written informed consent cola and caffeinated coffee (3.160.4 mg/kg caffeine/day) against was obtained from all participants before the study commenced.
water with a mixture of caffeinated colas (1.460.2 mg/kg The study was approved by the Science, Technology, Engineering caffeine/day) or non-caffeinated beverages [13]. The authors and Mathematics (STEM) Ethical Review Committee at the found no effects of coffee consumption compared with non- University of Birmingham, UK.
caffeinated beverages across a range of hydration markers incaffeine-habituated participants. Whilst the authors concluded that the advice to exclude caffeinated beverages from daily fluid Fifty-two healthy non-smoking males aged 18–46 y were requirement was not supported by their findings, the study did not accepted to participate in the study following the screening of measure total body water. Total body water (TBW) estimations over 100 volunteers. Inclusion criteria required participants to be using the doubly labelled water dilution technique is considered weight stable, pass a general health questionnaire, be free from the gold standard method for assessing body water fluctuations medications containing caffeine or those that might influence over time [14]. One recent study investigated the effects of caffeine weight or fluid-electrolyte balance, live and work in an environ- on TBW using deuterium oxide [19]. Thirty participants classified ment of ambient temperature with no significant temperature or as low caffeine users (,100 mg/day) consumed caffeine (5 mg/ humidity fluctuations, consume a diet with no extreme food, kg/day) or placebo tablets for 4 consecutive days. Although these beverage or dietary supplement intakes and be free from chronic participants could not be classified as ‘caffeine-habituated', no illnesses. Females were excluded from the study due to possible changes in TBW measured on day 1 and 4 were found between disruptions to fluid balance by the menstrual cycle. Participants PLOS ONE www.plosone.org January 2014 Volume 9 Issue 1 e84154 Coffee Ingestion and Fluid Balance were moderate coffee drinkers consuming 3–6 cups per day (300– Participants were $10 h fasted and had not consumed any fluids 600 mg/day caffeine) assessed by a 3-day weighed food diary.
since 21:30 the previous evening. Participants produced a first Two participants could not complete the study due to individual morning void (MV) (trial days 1–3) and a separate 24 h urine circumstances preventing them from visiting the laboratory.
collection (trial days 2–3). Nude body weight was recorded and avenous blood sample collected. Meals and snacks were consumed at standardised times (630 min); breakfast at 07:30–09:00 Participants reported to the School of Sport and Exercise (immediately post testing), morning snack at 10:30, lunch at Sciences, Human Performance Laboratory at the University of 13:30, afternoon snack at 16:30 and evening meal at 19:30.
Birmingham on two occasions prior to testing. Trials ran fromTuesdays to Fridays during the months of February to December.
On their first visit, participants were instructed how to complete a As there is no clear consensus on how much fluid an individual 3-day weighed diet diary and were provided with a set of digital should consume, yet fluid intake was required to be standardised scales (Electronic Scales; Salter Arc) to weigh their food and fluid for each participant, daily fluid intake was calculated based on intake accurately to 0.1 g. On their second visit, participants mean individual fluid intakes recorded over the 3-day diet dairy.
returned their completed diet diary and baseline body weight was Daily fluid intake was provided with bottled water and divided into recorded. Each participant completed two treatments each lasting six equal bottles, measured to the nearest gram using digital scales.
four consecutive days. Each trial was separated by a 10 day wash Participants consumed water at pre-determined time points; out period during which time participants were instructed to between 07:30–09:00 (post testing), 10:30, 13:30, 16:30, 19:30 consume their normal diet and daily caffeine intake. See figure 1 and 21:30. Test beverages were consumed at predetermined time for a schematic overview.
points; immediately after testing (07:30–09:00), 10:30, 13:30 and16:30. Each participant was provided with a mug marked at 200 mL. During trial C, participants received four pre-weighedcontainers of Nescafe´ Original coffee to provide 4 mg/kg BM of Each trial was undertaken in a counter balanced cross-over caffeine per day (2.360.4 g Nescafe´ Original per cup) and were design and participants were randomly allocated to a treatment instructed to make the beverage with boiled tap water to the group. The coffee trial (C) involved participants consuming four 200 mL marker in the mug provided. During trial W, participants mugs (200 mL) of black coffee per day (Nescafe´ Original) equating were instructed to consume 200 mL tap water in the same mug.
to a caffeine intake of 4 mg/kg BM. The water control trial (W) Total test beverage intake was 800 mL/day.
involved participants consuming four mugs of water (200 mL) perday. Participants were required to abstain from alcohol and all Measures and Analysis physical activity 24 h prior to and for the duration of each trial,with the exception of walking for transport.
Diet was controlled and provided to participants throughout Fasted blood samples (approximately 15 mL) were drawn from each testing period, including the control days. The same diet was a superficial vein (21G Venisystem short butterfly, NU Care), replicated and provided for each participant's second trial. Food typically from the median cubital vein by a trained phlebotomist and fluid intake recorded in the 3-day weighed food diary was following a 5 min resting period by participants in the supine analysed for macronutrients, sodium and potassium and food fluid position. Fasted blood samples were collected on the mornings of content using nutrition analysis software (Nutritionist Pro, Axxya test days 1–3. Blood for serum and plasma analysis were collected Systems). Diets were designed and prescribed on an individual directly into two separate tubes; one with clotting agent for basis to replicate mean energy and fluid intakes from the food analysis of serum sodium (Na+), potassium (K+), osmolality, diary. Diets were a standard weight-maintaining composition of creatinine, blood urea nitrogen (BUN) and deuterium oxide 50%:35%:15% for carbohydrate, fat and protein respectively. A (D2O) for total body water (TBW) calculation and one with compliance booklet was completed by participants on the morning K2EDTA for analysis of haematocrit, total plasma protein (TPP) of each trial day to ensure all food and beverages from the and caffeine. Haematocrit was analysed using a haematocrit previous day were consumed at the correct times and that no centrifuge (Micro Haematocrit Centrifuge, Hawksley & Sons Ltd.) unplanned exertions, fluid losses or nutritional variations had and ruler (Micro Haematocrit Tube Reader, Hawksley & Sons occurred. Participants were instructed to complete the Bristol Ltd.). All other samples were centrifuged at 3500 RPM for 15 min Stool Chart each morning for indications of disruption to fluid at 4uC. Plasma and serum were frozen at 220uC for later analysis.
balance [21]. On the morning of each trial, participants reported All samples were analysed in duplicate, with the exception of D2O.
to the laboratory at a standardised time between 07:00–09:00.
Serum osmolality was determined via freeze point depression via Figure 1. Overview of study design.
doi:10.1371/journal.pone.0084154.g001 PLOS ONE www.plosone.org January 2014 Volume 9 Issue 1 e84154 Coffee Ingestion and Fluid Balance the Advanced Osmometer Model 765 (Advanced Instruments Inc kilograms, the following equation was applied: TBW (kg) = TBW Norwood MA). TPP, serum creatinine and BUN were analysed (moles)618.02/1000 g. It is known that some deuterium binds to using the iLab 650 (Instrumentation Laboratory, UK). Plasma acidic amino acids of proteins or other non-exchangeable sites and caffeine was analysed for participant compliance using a reversed it has been experimentally determined that deuterium oxide High Performance Liquid Chromatography (HPLC) – UV overestimates TBW by 4% [24]. Therefore, to correct for the non- method, following the protocol described elsewhere [22] (City exchange of deuterium in the body, the TBW measurement was Hospital, Sandwell and West Birmingham Hospitals NHS Trust).
divided by 1.04.
Na+ and K+ were analysed using Ion Specific Electrodes on theiLab 600 (Midland Pathology Services). Samples were loaded into cuvettes and place into the iLab without pre-preparation and A total of five urine samples were collected during each trial; two 24 h collections (24 h) and three morning voids (V). V was collectedseparately each day and analysed for urine specific gravity (USG) Total Body Water and Body Mass using a hand held refractometer (Pocket Refractometer, PAL-105.
Nude body mass (BM) was recorded each morning (trial days 1– Atago, Japan) and volume using digital scales (measured to 0.01 g) 3) following the participants' first morning void. Participants were (Sartorius, AG Germany), applying the formula to correct for USG fasted and had not consumed any water since the previous (V = (M bottle plus urine collection2M empty bottle)/(USG6rH2O): V is volume (mL), M are masses (g) and rH2O = 1 g/mL is density of Labelled isotope D 2O, was provided for each participant to drink to enable the calculation of TBW (99.9 atom % D, Aldrich Twenty four hour urine collections were analysed for USG and Chemistry, Sigma-Aldrich). TBW was calculated on days 1 and 3 total volume using the methodology outlined above. In addition, of each trial to ensure participants began the study in a state of 24 h collections were further analysed for osmolality via freeze euhydration and to assess any disruptions to fluid balance over the point depression using the Advanced Osmometer Model 765 duration of the each trial.
(Advanced Instruments Inc. Norwood MA), creatinine on the iLab Participants were provided with 0.1 g/kg BM D 650 (Instrumentation Laboratory UK) and sodium (Na+) and to the nearest 0.001 g on day 0 (control day) and trial day 2.
potassium (K+) on the iLab 600 (Midlands Pathology Services Participants were instructed to consume the D Ltd.). The MV volume was added to the 24 h collection to give 2O between 20:30– 21:30 with their evening water allowance. No additional fluids total 24 h volume data (V24). Following the initial measures of were permitted following D urine volume and USG, urine samples were stored at 220uC for 2O ingestion until after the fasted blood sample was collected the next morning (trial days 1 and 3) later analysis.
approximately 10–12 h later. Participants were instructed to The numbers of urine samples reported throughout the paper continue to collect all urine losses. An additional blood sample are: Volume (n = 50), USG (n = 50), urine osmolality (n = 46), urine was taken on the evening of day 2 (between 17:00–18:00) prior to creatinine (n = 48), urine Na+ (n = 46) and urine K+ (n = 42). The the consumption of their second dose of D numbers of blood samples reported throughout the paper are: 2O to establish new blood deuterium enrichment baseline.
haematocrit (n = 48), serum osmolality (n = 49), total plasma protein (n = 48), serum creatinine (n = 46), serum sodium (n = 45) 2O enrichment was analysed using the Gas-Bench II (Thermo Electron, Bremen, Germany) – isotope mass spectrom- and serum potassium (n = 45). Sample sizes less than 50 are the etry (Finnigan, Delta XP, Bremen, Germany) following the result of missing samples or technical error.
protocol described elsewhere [23]. Briefly, 200 mL of plasma wasadded to a vacutainer (Labco, High Wycombe, England) with a Statistical Analysis platinum catalyst (Thermo Electron, Bremen, Germany). The All data were analysed using statistical software (SPSS. 18 for vacutainer was flushed by an automated autosampler-assisted Windows). Two-way repeated measures ANOVA with pairwise flushing procedure, using 2%H2 in Helium gas for 5 min.
comparisons post hoc were applied to each data set to look for Following this, a 40 min equilibrium period occurred whereby significant main effects. Delta values were calculated and Student's the hydrogen isotopes in the aqueous solution exchanged with t-tests were used to analyse changes overtime in each condition.
hydrogen ions in the headspace. A sample of the headspace gas The level of significance was set at p,0.05.
was then injected into the Isotope Ratio Mass Spectrometer(IRMS) (Thermo Electron, Bremen, Germany). A mean of the four middle measurements was taken as the measure for eachsample. The isotopic enrichment was expressed as d0 the international water standard Vienna Standard Mean Ocean Fifty of the fifty two participants recruited for this study fully Water (V-SMOW). The coefficient of variation of the measure- completed the two trials. The characteristics of the study ment was 0.027%. Results of the isotope ratio analysis were population are presented in table 2.
reported relative to the working reference gas versus V-SMOWand as atom percentage excess (APE).
The delta between sample and reference gas is defined as: Delta The habitual caffeine intake questionnaire and three day D = [(Ratio of Sample - Ratio of Reference)/(Ratio of Reference)]61000.
weighed diet diaries ensured participants were habitual moderate The delta deuterium values for the pre-dose (dpre) and post-dose coffee drinkers with estimated mean intakes of between 300– samples (dpos) were determined. The deuterium dose was diluted 600 mg caffeine per day from coffee. Any participant whose with tap water. The deuterium content of tap water (dtap) and the caffeine intake from coffee fell outside of this range was not dose (ddose) was measured. TBW in moles could then be included in the study.
calculated from the dilution of the heavy water isotope using the During trial C, participants consumed 4 mg/kg day caffeine equation: TBW (moles) = A/(18.02a)6[ddose - dtap/(dpost2dpre)]. A provided in the form of Nescafe´ Original, divided into four equal is the amount of dose (g) administered to participants and a is servings of 200 mL. During trial W, participants consumed amount of dose (g) diluted for analysis. To convert TBW to 200 mL tap water on four occasions each day. Total test beverage PLOS ONE www.plosone.org January 2014 Volume 9 Issue 1 e84154 Coffee Ingestion and Fluid Balance Table 2. Participant characteristics and pre-trial dietaryintakes.
Total Calorific Intake (Kcal) Dietary carbohydrate (%) Dietary Protein (%) Total Water Intake Figure 2. Mean total body water estimates from Day 1–Day 3.
Total Coffee Intake (mL) n = 25.
doi:10.1371/journal.pone.0084154.g002 however mean Na+ excretion was significantly higher on both days intake was 800 mL/day during both conditions. Mean caffeine in the coffee trial than the water trial (p = 0.02). K+ concentration consumption during trial C was 308 mg, and ranged from 204.4– was significantly higher on day 2 in both conditions (p = 0.02), but 453.0 mg caffeine.
no between-condition difference was found.
Compliance booklets suggest that all participants consumed the Neither urine void volume nor urine void USG were between foods and fluids that they were provided with. In addition, no conditions; p = 0.86 and p = 0.95, respectively (table 4).
participants partook in any physical activity, with the exception ofwalking for transport, 24 h prior to and throughout the duration of each trial. The Bristol Stool Chart monitored any unusual faecallosses. No participants reported unexpected fluid losses from Means and standard deviations of haematological measures diarrhoea or vomiting during either trial.
recorded on trial days 1, 2 and 3 are presented in table 5.
Haematological markers did not differ between conditions across Serum caffeine was measured on day two of each trial to check all measures: serum osmolality, haematocrit, total plasma protein, for participant compliance. Results of caffeine analysis, performed serum sodium, serum potassium (p,0.05). Student's t-test analysis by high performance liquid chromatography showed that, as showed no significant differences between conditions in the delta expected, serum caffeine was significantly higher in the coffee trial change from day 1 to day 3 for all haematological measures.
than the water trial (p,0.01). These findings support participantcompliance to the diet and test beverage during each trial.
Renal function was normal throughout each trial as assessed by urine creatinine (Table 3), serum creatinine and BUN (Table 5).
Dietary macronutrient intake was calculated individually for Neither urine or serum creatinine differed between conditions or each participant, based on energy from their food diary. Mean time points (p.0.05).
energy intake during the trials was 24256413 Kcal. Mean waterconsumption during the trials was 19536642 mL.
Body Mass Variables Individual daily fluid requirements, intakes and beverage Figure 2 illustrates the results of TBW estimates, based on preferences vary extensively within and across populations.
deuterium oxide analysis performed by gas chromatography mass Despite the lack of a consensus for how much fluid an individual spectrometry. Fluctuations in TBW were not significantly different should consume and the effects of various beverages on fluid between the two conditions (p = 0.90). There were no significant balance, there are widespread guidelines for optimal hydration changes in TBW from beginning to end of either trial (p.0.05) that are considered common knowledge [13]. Healthy adults are suggesting that participants maintained a stable fluid balance often advised to avoid caffeinated beverages due to the potential throughout the study. This is further confirmed by statistical negative impact they may have on hydration status [7]. These analysis showing no significant effect of trial day on either opinions and advisories are based upon a relatively small collection condition (p = 0.43).
of caffeine studies that have been publicised in both scientific and Figure 3 illustrates daily body mass measurements. Mean body lay literature and in the media over the past few decades [10,17,25]. Interestingly however, there is a lack of data that has 76.97612.15 kg. Mean body mass did not differ between the specifically investigated moderate doses of coffee in free living two conditions (p = 0.45), however a small but progressive daily fall healthy adults. Thus, the question of whether moderate coffee in BM occurred within both conditions (p,0.05). Mean decrease consumption can contribute to daily fluid requirement remains in BM from day 1 to day 3 across both trials was 0.3960.5 kg.
To our knowledge, this is the first study to directly compare the chronic effects of coffee ingestion with water against a wide range Means and standard deviations of 24 h urinary measures of hydration assessment techniques. We hypothesised that when recorded on trial days 1 and 2 are presented in table 3. Urine void ingested in moderation; coffee would contribute to daily fluid volume and USG are presented collected on trial days 1–3 are requirement and would not result in progressive dehydration over presented in table 4. Twenty four hour urine volume, USG, urine the course of 72 h. Our data shows no significant differences in the osmolality or urine creatinine did not differ between conditions hydrating properties of coffee or water across a wide range of (p.0.05). Urinary Na+ was not different between trials days, hydration assessment indices. No significant differences were PLOS ONE www.plosone.org January 2014 Volume 9 Issue 1 e84154 Coffee Ingestion and Fluid Balance Figure 3. Mean body mass. * Significant difference between days. n = 50.
doi:10.1371/journal.pone.0084154.g003 observed between conditions in any of the haematological free' water [30], particularly when producing a relatively large markers. No differences in blood urea nitrogen or serum creatinine volume of dilute urine as in the current study. Baseline urinary suggest renal function was normal throughout both trials. Analysis potassium was significantly elevated on day one of the coffee trial of urinary data showed no significant differences between compared to day one of the water trial. The potassium content in a conditions in 24 h urine volume, urine void volume, USG or cup of instant coffee (200 mL and ,2 g coffee) is approximately urine osmolality. Small daily fluctuations in TBW were observed 80 mg [30], thus participants consumed ,320 mg additional during both trials; however this did not reach significance in either potassium during the coffee trial than during the water trial. No condition. A very recent study investigated the effects of caffeine differences were observed between the conditions on day two, provided in capsules (5 mg/kg/day) on the TBW of 30 male which may suggest adaptive renal handling.
participants classified as ‘low-caffeine users' (,100 mg/day) [19].
Interestingly, although no changes were observed in TBW, the No differences in TBW were observed between the caffeine and data showed a small fall in body mass of 1906120 g/day in both placebo control group. Our data confirms the author's conclusions conditions (0.2% BM). Clinical dehydration is reported to be a that a moderate consumption of caffeine does not disrupt TBW.
body mass loss of between 1–3%, therefore whilst the 0.2% BM Urinary sodium was significantly higher in the coffee trial than decrease observed in this study did reach significance; participants the water trial on both days. The increased sodium excretion in were not near the level of clinical dehydration. These findings are the coffee trial falls in line with previous studies that have observed similar to the results of Grandjean et al who assessed hydration that both theophylline and caffeine enhance sodium excretion at status in 18 healthy adults consuming a mean caffeine intake of the proximal and distal renal tubules [26–28]. The increase in between 1.40–3.13 mg/kg BM [13]. The authors reported a mean sodium excretion is due to methyxanthine-induced natriuresis loss of 0.30% 0.39 BM across all test conditions. Authors suggested caused by inhibition of salt transport along the proximal that the loss was due to normal divergence or that their method of convoluted tubule [29]. While sodium excretion is an important determining treatment volumes caused a small level of dehydra- determinant of urine production, it is not the only driver of urine tion to occur. One strength of our study was that the individual volume. Some of the water in urine is derived from ‘osmotically fluid intake during the trials was based on three-day diet diaries Table 3. Twenty four hour urine collection.
Urine K excretion ± Urine Osmolality ± Urine Creatinine ± Urine Na excretion ± SD (total mmol/24 h) Values are means 6 SD.
*Coffee significantly higher than water.
{Day 2 significantly higher than day 1.
doi:10.1371/journal.pone.0084154.t003 PLOS ONE www.plosone.org January 2014 Volume 9 Issue 1 e84154 Coffee Ingestion and Fluid Balance Table 4. Urine void volume and USG.
Urine Void Volume Values are means 6 SD.
instead of a fixed volume for everyone. Furthermore, if partici- pants felt they were not allocated a sufficient volume of water atany point during the first trial or indeed if they had too much water, they were permitted to return to the laboratory to have their fluid allocation amended. The adjusted fluid intake was recorded and repeated during the second trial. The small losses inbody mass observed in this study are likely to be multifactorial. Assuggested by Grandjean et al [13], it is also possible that part of themass loss observed in this study was due to natural divergence orthat participants were not provided with sufficient water during the trials. The urinary data in the current study shows participants were producing relatively large amounts of dilute urine (urine osmolality,serum osmolality), which suggests dehydration isunlikely to be the cause of the fall in body mass. One otherpossible cause of the body mass loss could be due to unmeasuredfaecal losses. Participants completed a compliance booklet eachday which included questions regarding faecal losses and includedthe validated Bristol Stool Chart. Data collected from this booklet would highlight any unusual stool production, but as samples were not weighed it is not possible to know how much volume was excreted. No unusual faecal losses were reported by any of theparticipants.
This study is limited by the nature of its design. To achieve optimal results, a metabolic ward would have provided the mostcontrol of the environment and of the participants; however in an attempt to understand the effects of coffee consumption in a ‘free- living' setting, some control will always be lost. Furthermore, it may have been beneficial to continue the 24 h urine collection on the third day however this was not possible due to time constraintsand demands on the participants. It may have been interesting to include a decaffeinated coffee condition as this would haveidentified any differences specifically caused by caffeine in coffee and not any of the other bioactive components, however as we found minimal differences between coffee and water we believethat it is unlikely that we would have found any significant differences if we had included a decaffeinated coffee condition.
With acknowledgement of the study's limitations, results suggest that coffee did not result in dehydration when provided in amoderate dose of 4 mg/kg BW caffeine in four cups per day.
Thus, these data suggest that coffee, when consumed in moderation by caffeine habituated males contributes to daily fluid requirement and does not pose a detrimental effect to fluid balance. The advice provided in the public health domain regarding coffee intake and hydration status should therefore be updated to reflect these findings.
PLOS ONE www.plosone.org January 2014 Volume 9 Issue 1 e84154 Coffee Ingestion and Fluid Balance Author Contributions We would like to offer our gratitude to Charlie Matthews, Hayley Weaver Conceived and designed the experiments: SCK AEJ. Performed the and Yasmin Elhadidi for their support, dedication and diligence with data experiments: SCK. Analyzed the data: SCK AEJ AKB. Contributed collection during this study. We would also like to thank all participants for reagents/materials/analysis tools: SCK AEJ AKB. Wrote the paper: SCK.
their patience and compliance throughout this time consuming study.
Statistical analysis: SCK AKB AEJ. Editing of final paper: AKB AEJ.
Disclaimer: The research paper reflects the work and opinions of theauthors only.
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PLOS ONE www.plosone.org January 2014 Volume 9 Issue 1 e84154
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Available online @ www.actasatech.com acta SATECH 3(1): 25 - 28 (2009) Comparative study of Albendazole and Papaya seed in the control of Gastrointestinal Nematodes in Goats *Anaeto, M., G. O. Tayo, G. O. Chioma & A. A. Afolabi Department of Agriculture and Industrial Technology, Babcock University,