Diuretic potential of energy drinks

Flying high?-Exploring the effect of red bull on blood pressure after microsurgical breast reconstruction in a randomized controlled trial

BACKGROUND

A sufficiently high blood pressure (BP) is essential for flap perfusion after microsurgical breast reconstruction. However, postoperative hypotension is common after these procedures. Perioperative volume overload may increase flap-related complications, and postoperative vasopressor use may be limited depending on institutions. Red Bull has been shown to increase BP in several studies. We aimed to evaluate the effect of Red Bull on perfusion-related variables after microsurgical breast reconstruction.

METHODS

We conducted a multicenter, prospective, randomized controlled trial. Female patients undergoing unilateral microsurgical breast reconstruction from June 2020 to October 2022 were randomly assigned to the intervention or control groups. The intervention group received 250 ml of Red Bull 2 h after surgery and twice on postoperative day (POD) 1. The control group received 250 ml still water at the respective intervals. BP was measured using a 24-hour monitoring device. Vasopressor use, fluid balance, and flap outcomes were compared.

RESULTS

One hundred patients were included in the study. Both groups were comparable concerning age, body mass index, and caffeine consumption. Mean arterial and diastolic BP were significantly higher in the Red Bull group after the second drink in the morning of POD1 (p-value = 0.03 and 0.03, respectively). Vasopressor use was similar, with a tendency for less postoperative etilefrine in the Red Bull group (p-value = 0.08). No flap loss was observed.

CONCLUSIONS

We observed increased mean arterial and diastolic BP in the Red Bull group after the second drink. Red Bull may be a useful adjunct after microsurgical breast reconstruction.

LEVEL OF EVIDENCE

I, therapeutic.

Knowledge, attitude, and perception of energy drinks consumption among university students in Jordan

Energy drinks gained popularity after the launch of Red Bull in 1997. Different brands are now available and young adults mainly consume these drinks. This study assesses the knowledge, attitude, and perception of energy drink consumption among university students in Jordan. A validated online survey was used to collect the required data, extracted from Google Forms into an Excel spreadsheet and statistically analysed using Statistical Package for Social Sciences version 24.0. A nationally representative sample of university students with a mean age of 22⋅2 ± 3⋅9 years (n 749) was obtained. The participating students demonstrated a neutral level of knowledge about energy drinks, as the mean score of knowledge = 7⋅1 ± 2⋅2 (out of 12), with 66 % (n 498) of them having consumed energy drinks and experienced their effects. Generally, the study's participants demonstrated a neutral attitude towards energy drinks and 70⋅5 % (n 528) acknowledged that energy drinks increase activity, but more than 70 % of them believed that energy drinks have harmful side effects. It was found that there is a significant (P-value <0⋅5) positive correlation between knowledge score and female gender, studying a medical major, and monthly income. The main reasons for consuming energy drinks were reported to be: to stay awake for longer, help study, and become more energetic. There is a need for more structured awareness campaigns to warn students about the possible side effects of these products in order to reduce the consumption and popularity of these drinks among students.

Effect of the Red Bull Energy Drink on Perfusion-Related Variables in Women Undergoing Microsurgical Breast Reconstruction: Protocol and Analysis Plan for a Prospective, Multicenter Randomized Controlled Trial

BACKGROUND

Maintaining a sufficiently high systolic blood pressure is essential for free flap perfusion after microsurgical breast reconstruction. Yet, many women undergoing these procedures have low postoperative systolic blood pressure. Intravenous volume administration or vasopressors may be needed to maintain systolic blood pressure above a predefined threshold. However, excessive volume administration may lead to volume overload and flap stasis, and the postoperative use of vasopressors may be limited depending on institutional standards. Additional nonpharmacological measures to raise blood pressure might be beneficial. Evidence suggests that the Red Bull energy drink could raise blood pressure. It has been shown to increase systolic and diastolic blood pressure in healthy volunteers and athletes.

OBJECTIVE

The primary objective of this study is to determine the difference in systolic blood pressure between an intervention group receiving Red Bull and a control group receiving still water after microsurgical breast reconstruction. Secondary objectives include postoperative heart rate, 24-hour fluid balance, pain level, or necessity for revision surgery due to flap complications.

METHODS

The Red Bull study is a prospective, multicenter randomized controlled trial comparing the effect of postoperative ingestion of Red Bull energy drink against still water in female patients undergoing unilateral microsurgical breast reconstruction. A total of 250 mL of Red Bull (intervention group) or 250 mL of still water (control group) will be administered to the study participants 2 hours postoperatively as well as for breakfast and lunch on postoperative day 1, amounting to a total volume of 750 mL per 24 hours. Female patients between 18 and 70 years of age undergoing unilateral microsurgical breast reconstruction will be included. Exclusion criteria are a history of arterial hypertension, cardiac rhythm disorder, diabetes mellitus, gastric or duodenal ulcer, thyroid disease, and current use of antihypertensive or antiarrhythmic drugs or thyroid hormones, as well as intolerance to Red Bull.

RESULTS

Recruitment for the study started in June 2020 and was completed in December 2022. There is evidence that the Red Bull energy drink increases blood pressure in healthy volunteers and athletes. We hypothesize that postoperative ingestion of Red Bull will increase systolic blood pressure in women after microsurgical breast reconstruction. Red Bull could hence be used as a nonpharmacological adjunct to vasopressors or volume administration in women with hypotensive blood pressure after microsurgical breast reconstruction.

CONCLUSIONS

This paper describes the Red Bull study trial protocol and analysis plan. The information will increase the transparency of the data analysis for the Red Bull study.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04397419; https://clinicaltrials.gov/ct2/show/NCT04397419.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/38487.

Prevalence of Voice Problems and Associated Risk Factors Among Tamil-Speaking Imams

PURPOSE

Voice of Professional Voice Users (PVUs) are of particular interest to practicing Speech-Language Pathologists. There is a dearth of studies concerning the prevalence of voice disorders and the associated risk factors among Tamil-speaking Imams. We address this research gap using non-experimental survey research.

METHODS

A questionnaire was framed by reviewing earlier literature. The derived questionnaire was administered to one hundred Tamil-speaking Imams actively involved in religious service in Tamil Nadu. We analyzed the obtained responses quantitatively and qualitatively. We also examined the effect of age on the prevalence of voice disorders and associated risk factors.

RESULTS

Based on survey responses, the career prevalence of voice problems among Tamil-speaking Imams was as high as 89%, and the point prevalence was 64%. The general health status of the Imams were good. However, vocal health was not satisfactory. This study identified several factors that contribute to voice problems, such as constant use of loud voice, acid reflux, unhealthy vocal habits, and insufficient hydration. A positive aspect observed during this study was the absence of smoking and consumption of alcohol among Imams. Even though the Imams presented good awareness of the voice production mechanism, they reported not seeking medical help when facing a voice problem. Current findings report a minimal impact of age-related differences on associated risk factors for voice disorders among the Imams.

CONCLUSIONS

Voice disorders are prevalent among Tamil-speaking Imams. Several risk factors leading to voice disorders among these individuals need to be addressed.

Effects of roasting on bioavailability and bioactivities of Vigna angularis and potential of coffee-like beverage

Containing similar aroma and flavor profile of coffee after roasting, Vigna angularis have potential to be a caffeine-free coffee-like beverage. Microwave roasting process was conducted in a microwave oven at 600 W for 7, 14, and 21 min at 2-min intervals, and fluidized bed roasting process was conducted in a fluidized bed roaster at 200°C for 9, 18, and 27 min. In order to compare the roasted beans, color, fat, ash, crude protein, crude fiber, antioxidant activity, and total phenolic content measurements were performed. In addition, effects of roasting methods on protein bioavailability and antinutritional factors were investigated. Sensory test was conducted to compare the coffee and coffee-like beverages. Fluidized-bed roasted beans had higher scores than microwave roasted beans in terms of sensory acceptability (p ≤ 0.05). Roasting process increased the total phenolic contents up to 25.32 (mg GAE/g) and the protein bioavailability up to 89.82 ± 0.11%. The results of this study revealed that roasting can be used as a tool to increase nutritive value, bioavailability, antioxidant activity, and potential of coffee-like beverage of V. angularis. PRACTICAL APPLICATION: Since Vigna angularis beans contain similar aroma and flavor profile of the coffee after roasting, they have a potential to be a caffeine-free coffee alternative. Although coffee is very popular in demand, most of the coffee drinkers think that caffeine is very harmful. Having similar sensory scores as coffee beverages in certain roasting degrees, V. angularis beverages could be a delicious caffeine-free alternative.

Acute caffeine supplementation improves jumping, sprinting, and change-of-direction performance in basketball players when ingested in the morning but not evening

This study compared the effects of acute caffeine supplementation (3 mg/kg) administered in the morning and evening on performance-related variables in basketball players. Eleven, national-level, adolescent male basketball players underwent field-based fitness testing on four occasions: morning (10:00) with caffeine ingestion (AM_CAFF), morning (10:00) with placebo ingestion (AM_PLAC), evening (21:00) with caffeine ingestion (PM_CAFF), and evening (21:00) with placebo ingestion (PM_PLAC). Fitness testing included of a countermovement jump without arm swing (CMJ), CMJ with arm swing (CMJAS), squat jump (SJ), Lane Agility Drill (LAD), 20-m linear sprint, and Suicide Run with (SRD) and without dribbling (SR). Data were analysed using two-way repeated measures analyses of variance and paired t-tests, with effect sizes (ES) also determined for all pairwise comparisons. Follow-up t-test comparisons revealed that AM_CAFF produced small-moderate, significant (p<0.001), improvements in CMJ (ES = 0.51), CMJAS (ES = 0.40), SJ (ES = 0.51), and SR (ES = -0.45) compared to AM_PLAC. AM_CAFF also produced a moderate, significantly (p<0.001) faster LAD (ES = -0.61) compared to PM_CAFF. PM_PLAC demonstrated small-moderate, significant (p<0.05) improvements in CMJ (ES = 0.43), CMJAS (ES = 0.48), and 20-m sprint (ES = -0.63) compared to AM_PLAC. In contrast, AM_PLAC resulted in large, significantly (p<0.001), faster SRD (ES = -1.46) and SR (ES = -1.59) compared to PM_PLAC. Given the ergogenic effects of caffeine during basketball-specific fitness tests appear to be influenced by time of ingestion, basketball practitioners should consider administering caffeine only to players in the morning to improve vertical jump, sprinting, and change-of-direction performance, with no beneficial effects observed with caffeine ingestion in the evening.Highlights The effect of caffeine supplementation on basketball-specific performance related variables were mediated by ingestion time in elite, adolescent basketball players.AMCAFF produced small-moderate improvements in vertical jump, change-of-direction, 20-m linear sprint, and repeated-sprint performance compared to AMPLAC while PMCAFF produced trivial differences in each performance-related variable compared to PMPLAC.Comparisons between ingestion times in the placebo condition revealed vertical jump height and 20-m sprint speed were impaired in the morning compared to the evening, but these time-dependent differences were eliminated when caffeine was consumed in the morning.Basketball practitioners should consider administering caffeine only to players in the morning to improve vertical jump, sprinting, and change-of-direction performance, with no beneficial effects observed with caffeine ingestion in the evening.

Impact of food and drinks on urine production: A systematic review

CONTEXT

The impact of food and drinks on body fluid metabolism is of direct clinical relevance but current evidence remains fragmented.

AIM

Synthesise current evidence on the role of food and drinks in urine production.

METHODS

Systematic review as per PRISMA guidelines using MEDLINE and EMBASE databases (completed October 2019). Studies reporting on the effect of food, food constituents, and drinks on urine production were included. Two authors performed an independent extraction of relevant articles using predetermined data sets and completed quality-of-study indicators.

RESULTS

A total of 49 studies were included, of which 21 enroled human subjects, and 28 were clinically relevant animal studies (all of which utilised rodent models). The included studies were determined to be of variable quality. High dietary sodium, as well as wine, spirits, high-caffeine coffee, and caffeinated energy drinks, increased urine production in human studies. Decreased urine production was associated with low dietary sodium and consumption of milk, orange juice, and high-salt/high-sugar drinks. In animal models, a variety of fruits, vegetables, herbs, spices, and honey were associated with increased urine production.

CONCLUSION

Current evidence suggests that although several types of food and drinks may impact body fluid metabolism, the quality of the data is variable. Urine production appears to be influenced by multiple factors including composition (ie, moisture, macronutrients, and electrolytes), metabolite load, and the presence of specific diuresis-promoting substances (eg, caffeine, alcohol) and other bioactive phytochemicals. Future research is needed to support current evidence and the physiologic mechanisms underlying these findings.

An interprofessional approach to managing children with treatment-resistant enuresis: an educational review

Enuresis (intermittent urinary incontinence during sleep in a child aged ≥ 5 years) is commonly seen in paediatric practice. Despite the availability of effective interventions, treatment resistance is encountered in up to 50% of children. In this educational review we attempt to provide insight into the causes of treatment resistance, and offer practical suggestions for addressing this condition using an interprofessional approach. We explore the pathophysiology of and standard treatments for enuresis and discuss why standard treatments may fail. An interprofessional approach to treatment resistance is proposed which utilises the expertise of professionals from different disciplines to address the problems and barriers to treatment. The two interprofessional approaches include a multidisciplinary approach that involves the patient being sent to experts in different disciplines at different times to address their treatment resistance utilising the skills of the respective experts, and an interdisciplinary approach that involves a patient being managed by members of interdisciplinary team who integrate their separate discipline perspectives into a single treatment plan. Although an interdisciplinary approach is ideal, interdisciplinary teams may not be available in all circumstances. Understanding the roles of other disciplines and engaging clinicians from other disciplines when appropriate can still be helpful when treatment resistance is encountered.

Tips for managing treatment-resistant enuresis

Enuresis (bedwetting) is common in school-aged children and can impact health, psychosocial well-being and quality of life. Although effective treatment is available, treatment resistance is encountered in about 50%. This paper discusses the management of treatment-resistant enuresis from a multidisciplinary perspective. Causes of treatment resistance include lower urinary tract problems, constipation, incorrect alarm training techniques, sleep disorders including sleep apnoea and psychological comorbidities. Practical suggestions to address treatment resistance are offered utilising expertise from clinicians from different disciplines.

Pharmacological potential of methylxanthines: Retrospective analysis and future expectations

Methylated xanthines (methylxanthines) are available from a significant number of different botanical species. They are ordinarily included in daily diet, in many extremely common beverages and foods. Caffeine, theophylline and theobromine are the main methylxanthines available from natural sources. The supposedly relatively low toxicity of methylxanthines, combined with the many beneficial effects that have been attributed to these compounds through time, generated a justified attention and a very prolific ground for dedicated scientific reports. Methylxanthines have been widely used as therapeutical tools, in an intriguing range of medicinal scopes. In fact, methylxanthines have been/were medically used as Central Nervous System stimulants, bronchodilators, coronary dilators, diuretics and anti-cancer adjuvant treatments. Other than these applications, methylxanthines have also been hinted to hold other beneficial health effects, namely regarding neurodegenerative diseases, cardioprotection, diabetes and fertility. However, it seems now consensual that toxicity concerns related to methylxanthine consumption and/or therapeutic use should not be dismissed. Taking all the knowledge and expectations on the potential of methylxanthines into account, we propose a systematic look at the past and future of methylxanthine pharmacologic applications, discussing all the promise and anticipating possible constraints. Anyways, methylxanthines will still substantiate considerable meaningful research and discussion for years to come.

Exposure and perceptions of marketing for caffeinated energy drinks among young Canadians

OBJECTIVE

To examine exposure to energy drink marketing among youth and young adults, and test perceptions of energy drink advertisements (ads) regarding target audience age and promoting energy drink use during sports.

DESIGN

A between-group experiment randomly assigned respondents to view one of four energy drink ads (sport-themed or control) and assessed perceptions of the ad. Regression models examined marketing exposure and perceptions.

SETTING

Online survey (2014).

SUBJECTS

Canadians aged 12-24 years (n 2040) from a commercial panel.

RESULTS

Overall, 83 % reported ever seeing energy drink ads through at least one channel, including on television (60 %), posters/signs in stores (49 %) and online (44 %). Across experimental conditions, most respondents (70·1 %) thought the ad they viewed targeted people their age or younger, including 42·2 % of those aged 12-14 years. Two sport-themed ads were more likely to be perceived as targeting a younger audience (adjusted OR (95 % CI): 'X Games' 36·5 %, 4·16 (3·00, 5·77); 'snowboard' 19·2 %, 1·50 (1·06, 2·13)) v. control (13·3 %). Participants were more likely to believe an ad promoted energy drink use during sports if they viewed any sport-themed ad ('X Games' 69·9 %, 8·29 (6·24, 11·02); 'snowboard' 76·7 %, 11·85 (8·82, 15·92); 'gym' 66·8 %, 7·29 (5·52, 9·64)) v. control (22·0 %). Greater reported exposure to energy drink marketing was associated with perceiving study ads as promoting energy drink use during sports.

CONCLUSIONS

Energy drink marketing has a high reach among young people. Ads for energy drinks were perceived as targeting youth and promoting use during sports. Such ads may be perceived as making physical performance claims, counter to Canadian regulations.

The Safety of Ingested Caffeine: A Comprehensive Review

Caffeine is the most widely consumed psychoactive drug in the world. Natural sources of caffeine include coffee, tea, and chocolate. Synthetic caffeine is also added to products to promote arousal, alertness, energy, and elevated mood. Over the past decade, the introduction of new caffeine-containing food products, as well as changes in consumption patterns of the more traditional sources of caffeine, has increased scrutiny by health authorities and regulatory bodies about the overall consumption of caffeine and its potential cumulative effects on behavior and physiology. Of particular concern is the rate of caffeine intake among populations potentially vulnerable to the negative effects of caffeine consumption: pregnant and lactating women, children and adolescents, young adults, and people with underlying heart or other health conditions, such as mental illness. Here, we review the research into the safety and safe doses of ingested caffeine in healthy and in vulnerable populations. We report that, for healthy adults, caffeine consumption is relatively safe, but that for some vulnerable populations, caffeine consumption could be harmful, including impairments in cardiovascular function, sleep, and substance use. We also identified several gaps in the literature on which we based recommendations for the future of caffeine research.

Caffeine Consumption and General Health in Secondary School Children: A Cross-sectional and Longitudinal Analysis

Although caffeine is sometimes associated with beneficial effects in adults, the substance may be dangerous if intake is too high. This concern is particularly relevant in regards to children and adolescents, as consumption of energy drinks may be particularly high in such populations. For this reason, the current study examined data from the Cornish Academies Project to determine whether caffeine intake in secondary school children was related to responses to a single-item measure of general health. Two cross-sections of data were available: questionnaires were completed by 2030 at baseline, by 2307 at 6-month follow-up, and by 1660 at both time-points. Relationships were, therefore, explored both cross-sectionally and longitudinally. High caffeine consumption (i.e., 1000 mg/week) was associated with low general health in both cross-sections of data, and analyses of individual caffeine sources suggested that the effects related specifically to cola and energy drinks. However, after controlling for additional aspects of diet, demography, and lifestyle, total weekly intake only remained significantly associated with general health at the latter time-point. Further to this, null findings from cross-lag and change-score analyses suggest that caffeine and general health were unlikely to be causally linked in this sample. However, due to methodological limitations, such as the two cross-sections of data being collected only 6 months apart, it is suggested that further longitudinal and intervention studies are required in order for firm conclusions to be drawn.

Effect of energy drink intake before exercise on indices of physical performance in untrained females

Objectives:

To determine the effect of energy drink consumption before exercise on indices of physical performance in untrained females.

Methods:

This single blind placebo controlled experimental study was carried out at the Physiology Department, University of Dammam, Dammam, Kingdom of Saudi Arabia from September 2011 to May 2012, on 32 healthy female students, in a crossover design. They were given either a standardized energy drink or the placebo 45 minutes before the exercise. Time to exhaustion and the stages of Bruce protocol achieved were noted. Heart rate, blood pressure, peripheral capillary oxygen saturation, and blood lactate were recorded before and after the exercise. Maximum oxygen consumption (VO₂max) was calculated by formula. Paired sample t-test was used for statistics.

Results:

The mean age was 19.93±0.8 years, mean height 156.40±3.83 cm, and the mean weight 51.73±3.65 kg. Time to exhaustion in the placebo group was 11.67±1.51 minutes and 11.41±1.56 in the energy drink group (p<0.157). The VO₂max in the placebo group was 34.06±6.62, while it was 32.89±6.83 in the energy drink group (p<0.154). There were no significant differences between the placebo and the energy drinks groups in regards to heart rate, blood pressure, and blood lactate levels, before or after the exercise. However, there were significant differences before, immediately, and 30 minutes post exercise for all parameters between each group.

Conclusion:

The effects of energy drinks intake on physical performance during the exercise in our small sample does not significantly differ from placebo.

Knowledge, Attitudes, and Practices on Energy Drink Consumption and Side Effects in a Cohort of Medical Students

The purpose of this study was to evaluate knowledge, attitudes, and practices concerning energy drink consumption and the prevalence of side effects among medical students. Twenty-two percent of respondents were regular users, particularly men (p < .0005). Users were younger (p = .027) and drank alcohol more frequently (p = .008) than "non-users." Forty-nine percent consumed alcohol associated with energy drinks. Forty-five percent of medical students declared side effects after energy drink consumption, such as palpitations (35%), insomnia (21%), and irritability (20%). The study confirms a large use of energy drinks among students and the occurrence of side effects. The use of energy drinks may influence the ingestion of large amounts of alcohol.

Performance outcomes and unwanted side effects associated with energy drinks

Energy drinks are increasingly popular among athletes and others. Advertising for these products typically features images conjuring great muscle power and endurance; however, the scientific literature provides sparse evidence for an ergogenic role of energy drinks. Although the composition of energy drinks varies, most contain caffeine; carbohydrates, amino acids, herbs, and vitamins are other typical ingredients. This report analyzes the effects of energy drink ingredients on prolonged submaximal (endurance) exercise as well as on short-term strength and power (neuromuscular performance). It also analyzes the effects of energy drink ingredients on the fluid and electrolyte deficit during prolonged exercise. In several studies, energy drinks have been found to improve endurance performance, although the effects could be attributable to the caffeine and/or carbohydrate content. In contrast, fewer studies find an ergogenic effect of energy drinks on muscle strength and power. The existing data suggest that the caffeine dose given in studies of energy drinks is insufficient to enhance neuromuscular performance. Finally, it is unclear if energy drinks are the optimal vehicle to deliver caffeine when high doses are needed to improve neuromuscular performance.

Caffeine-induced diuresis and natriuresis is independent of renal tubular NHE3

Caffeine is one of the most widely consumed behavioral substances. We have previously shown that caffeine- and theophylline-induced inhibition of renal reabsorption causes diuresis and natriuresis, an effect that requires functional adenosine A1 receptors. In this study, we tested the hypothesis that blocking the Gi protein-coupled adenosine A1 receptor via the nonselective adenosine receptor antagonist caffeine changes Na(+)/H(+) exchanger isoform 3 (NHE3) localization and phosphorylation, resulting in diuresis and natriuresis. We generated tubulus-specific NHE3 knockout mice (Pax8-Cre), where NHE3 abundance in the S1, S2, and S3 segments of the proximal tubule was completely absent or severely reduced (>85%) in the thick ascending limb. Consumption of fluid and food, as well as glomerular filtration rate, were comparable in control or tubulus-specific NHE3 knockout mice under basal conditions, while urinary pH was significantly more alkaline without evidence for metabolic acidosis. Caffeine self-administration increased total fluid and food intake comparably between genotypes, without significant differences in consumption of caffeinated solution. Acute caffeine application via oral gavage elicited a diuresis and natriuresis that was comparable between control and tubulus-specific NHE3 knockout mice. The diuretic and natriuretic response was independent of changes in total NHE3 expression, phosphorylation of serine-552 and serine-605, or apical plasma membrane NHE3 localization. Although caffeine had no clear effect on localization of the basolateral Na(+)/bicarbonate cotransporter NBCe1, pretreatment with DIDS inhibited caffeine-induced diuresis and natriuresis. In summary, NHE3 is not required for caffeine-induced diuresis and natriuresis.

[Abuse of energy drinks: does it pose a risk?]

BACKGROUND

Energy drinks designate "any product in the form of a drink or concentrated liquid containing a mixture of ingredients having the property to raise the level of energy and liveliness". Their introduction has raised many reluctance and reserves after numerous cardiovascular and neurological injuries among regular consumers.

OBJECTIVE

This article attempts to synthesize the existing literature on energy drinks. The review focuses to show that excessive energy drinks consumption cause many complications.

METHODS

The literature review was conducted from 2001 to 2014, using PubMed, Google Scholar, EMBASE, and PsycInfo, using the following keywords alone or combined: energy drinks, caffeine, taurine, toxicity, dependence, complications.

RESULTS

Occasional or moderate consumption of these cans seem to present little risk to healthy adults. However, their repeated consumption in proportions that far exceed the recommendations for recommended use by the manufacturers, combined with the use of alcohol or illicit drugs consumption increases the risk of occurrence of somatic and psychiatric complications, especially among underage, and subjects with cardiovascular and neurological history.

CONCLUSION

Repeated consumption of energy drinks increases the risk of somatic and psychiatric complications. Further studies must be controlled to improve our understanding of other possible negative consequences on health.

Adenosine, type 1 receptors: role in proximal tubule Na+ reabsorption

Adenosine type 1 receptor (A1 -AR) antagonists induce diuresis and natriuresis in experimental animals and humans. Much of this effect is due to inhibition of A1 -ARs in the proximal tubule, which is responsible for 60-70% of the reabsorption of filtered Na(+) and fluid. Intratubular application of receptor antagonists indicates that A1 -AR mediates a portion of Na(+) uptake in PT and PT cells, via multiple transport systems, including Na(+) /H(+) exchanger-3 (NHE3), Na(+) /PO4(-) co-transporter and Na(+) -dependent glucose transporter, SGLT. Renal microperfusion and recollection studies have shown that fluid reabsorption is reduced by A1 -AR antagonists and is lower in A1 -AR KO mice, compared to WT mice. Absolute proximal reabsorption (APR) measured by free-flow micropuncture is equivocal, with studies that show either lower APR or similar APR in A1 -AR KO mice, compared to WT mice. Inhibition of A1 -ARs lowers elevated blood pressure in models of salt-sensitive hypertension, partially due to their effects in the proximal tubule.

Energy drink usage among university students in a Caribbean country: Patterns of use and adverse effects

Objective: There has been little inquiry addressing whether or not concerns about adverse effects of energy drink usage are relevant in the Caribbean. This survey investigated energy drink usage and adverse consequences among tertiary level students in Trinidad and Tobago.

Methods: A cross-sectional survey of 1994 students from eight institutions was conducted using a de novo questionnaire based on findings from a focus group of students. Chi-squared analyses and logistic regression were used to assess relationships between energy drink usage, adverse effects and other factors affecting energy drink use, and to verify predictors of energy drink use.

Results: Prevalence of use was 86%; 38% were current users. Males were more likely to use, used more frequently and at an earlier age. Energy drinks were used most commonly to increase energy (50%), combat sleepiness (45%) and enhance academic performance (40%), and occurred during sports (23%) and mixed with alcohol (22.2%). The majority (79.6%) consumed one energy drink per sitting; 62.2% experienced adverse effects, most commonly restlessness (22%), jolt and crash (17.1%) and tachycardia (16.6%). Awareness of adverse effects was associated with no use (p = 0.004), but adverse effects were not a deterrent to continued use.

Conclusion: Energy drink usage is prevalent among students. The use is not excessive, but associated with high rates of adverse effects and occurs in potentially dangerous situations like during exercise and with alcohol. There is a need to educate students about the potential adverse effects of energy drinks.

The effect of caffeine on postoperative urinary retention after joint replacement surgery

BACKGROUND

Review of data on complications following joint replacement surgery revealed that urinary retention is a potential cause of increased morbidity. Repeat catheterizations, urinary tract infections, and possible infection of the prosthetic joint can result in a prolonged hospital length of stay. This study examined the effect of warm caffeinated coffee on a patient's ability to spontaneously void after indwelling catheter removal and the correlation between bladder volume and the ability to void spontaneously.

METHODS

This was a randomized, controlled, pilot study of subjects who underwent unilateral total knee arthroplasty or total hip arthroplasty. The indwelling catheter was removed postoperative day 1. If unable to void within 3 hours, participants were randomized into a control group and an intervention group. At scheduled intervals, the control group consumed 8 oz of warm water and the intervention group consumed 8 oz of caffeinated coffee.

RESULTS

Thirty subjects were randomized; 14 were randomized to the water group and 16 to the caffeine group. Twenty-four subjects spontaneously voided after ingestion of fluid and six required straight catheterization. Of these six, five of the subjects had ingested water and one subject had ingested coffee. For those who spontaneously voided, there was not a significant difference between the caffeine group and the water group. There was a significant difference between caffeine ingestion and the volume of the void.

DISCUSSION

Findings from this study suggest that ingestion of caffeine after removal of an indwelling urinary catheter in the postoperative patient may increase the amount of voiding volumes initially, therefore avoiding the need for straight catheterization. To accurately assess this, extending the study into postoperative day 2 would allow us to evaluate whether lower voiding volumes lead to the need for catheterization.

Effect of taurine and potential interactions with caffeine on cardiovascular function

The major impetus behind the rise in energy drink popularity among adults is their ability to heighten mental alertness, improve physical performance and supply energy. However, accompanying the exponential growth in energy drink usage have been recent case reports and analyses from the National Poison Data System, raising questions regarding the safety of energy drinks. Most of the safety concerns have centered on the effect of energy drinks on cardiovascular and central nervous system function. Although the effects of caffeine excess have been widely studied, little information is available on potential interactions between the other active ingredients of energy drinks and caffeine. One of the active ingredients often mentioned as a candidate for interactions with caffeine is the beta-amino acid, taurine. Although taurine is considered a conditionally essential nutrient for humans and is thought to play a key role in several human diseases, clinical studies evaluating the effects of taurine are limited. However, based on this review regarding possible interactions between caffeine and taurine, we conclude that taurine should neutralize several untoward effects of caffeine excess. In agreement with this conclusion, the European Union's Scientific Committee on Food published a report in March 2003 summarizing its investigation into potential interactions of the ingredients in energy drinks. At the cardiovascular level, they concluded that "if there are any interactions between caffeine and taurine, taurine might reduce the cardiovascular effects of caffeine." Although these interactions remain to be further examined in humans, the physiological functions of taurine appear to be inconsistent with the adverse cardiovascular symptoms associated with excessive consumption of caffeine-taurine containing beverages.

No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population

It is often suggested that coffee causes dehydration and its consumption should be avoided or significantly reduced to maintain fluid balance. The aim of this study was to directly compare the effects of coffee consumption against water ingestion across a range of validated hydration assessment techniques. In a counterbalanced cross-over design, 50 male coffee drinkers (habitually consuming 3–6 cups per day) participated in two trials, each lasting three consecutive days. In addition to controlled physical activity, food and fluid intake, participants consumed either 4×200 mL of coffee containing 4 mg/kg caffeine (C) or water (W). Total body water (TBW) was calculated pre- and post-trial via ingestion of Deuterium Oxide. 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 to end of either trial and no differences between trials (51.5±1.4 vs. 51.4±1.3 kg, for C and W, respectively). No differences were observed between trials across any haematological markers or in 24 h urine volume (2409±660 vs. 2428±669 mL, for C and W, respectively), USG, osmolality or creatinine. Mean urinary Na⁺ excretion was higher in C than W (p = 0.02). No significant differences in BM were found between conditions, although a small progressive daily fall was observed within both trials (0.4±0.5 kg; p<0.05). Our data show that there were no significant differences across a wide range of haematological and urinary markers of hydration status between trials. These data suggest that coffee, when consumed in moderation by caffeine habituated males provides similar hydrating qualities to water.

Assessment of pattern for consumption and awareness regarding energy drinks among medical students

BACKGROUND

Energy drink is a type of beverage which contains stimulant drugs chiefly caffeine and marketed as mental and physical stimulator. Coffee, tea, soft drinks and other caffeinated beverages are not considered as energy drinks. Purpose of our study was to evaluate the awareness of medical students regarding energy drinks and their pattern and reason of energy drinks consumption.

METHODS

This was a cross sectional and observational study conducted during the period of January - December 2012 at four Medical Colleges (Dow Medical College, Sindh Medical College, Jinnah Medical College and Liaquat National Medical College) of Karachi, Pakistan. Over all 900 M.B.B.S students were invited to participate after taking written consent but viable questionnaire was submitted by 866 students, estimated response rate of 96%. All data was entered and analyzed through SPSS version 19.

RESULT

Out of 866 participants, majority were females 614 (70.9%) and only 252 (28.5%) were males, with a mean age of 21.43 ± 1.51 years. Energy drinks users were 350 (42.89%) and non users were 516 (59.58%). Only 102 (29.3%) users and 159 (30.7%) non users know the correct definition of Energy drinks. Regarding awareness, mostly user and non users thought that usage of energy drinks had been on rise due to its usefulness in reducing sleep hours [users193 (43.9%), nonusers 247 (56.1%) (p < 0.05)], for studying or completing major projects [users184 (45.0%), nonusers 225 (55.0%) (p < 0.05)] and for refreshment purposes [users179 (44.9%), nonusers 220 (55.1%) (p < 0.05)]. Two main reasons of not using energy drinks by non-users were "awareness from its side effects" 247 (47.8%) and "have no specific reason" 265 (51.3%). Most common side effects reported by users were fatigue 111 (31.7%) and weight gain 102 (29.4%).

CONCLUSION

In sum, the fact that despite serious side effects of weight gaining and fatigue, practice of consuming energy drinks is highly prevalent among medical students, particularly because they are ever ready to boost their energy level and reduce sleep hours due to stress of exams and projects. This warrants the creation of continued public health awareness about the appropriate use of caffeinated beverages, their potential benefits, side effects and correction of wrong perceptions.

Caffeinated Alcoholic Beverages - An Emerging Trend in Alcohol Abuse

Alcohol use disorders are pervasive in society and their impact affects quality of life, morbidity and mortality, as well as individual productivity. Alcohol has detrimental effects on an individual’s physiology and nervous system, and is associated with disorders of many organ and endocrine systems impacting an individual’s health, behavior, and ability to interact with others. Youth are particularly affected. Unfortunately, adolescent usage also increases the probability for a progression to dependence. Several areas of research indicate that the deleterious effects of alcohol abuse may be exacerbated by mixing caffeine with alcohol. Some behavioral evidence suggests that caffeine increases alcohol drinking and binge drinking episodes, which in turn can foster the development of alcohol dependence. As a relatively new public health concern, the epidemiological focus has been to establish a need for investigating the effects of caffeinated alcohol. While the trend of co-consuming these substances is growing, knowledge of the central mechanisms associated with caffeinated ethanol has been lacking. Research suggests that caffeine and ethanol can have additive or synergistic pharmacological actions and neuroadaptations, with the adenosine and dopamine systems in particular implicated. However, the limited literature on the central effects of caffeinated ethanol provides an impetus to increase our knowledge of the neuroadaptive effects of this combination and their impact on cognition and behavior. Research from our laboratories indicates that an established rodent animal model of alcoholism can be extended to investigate the acute and chronic effects of caffeinated ethanol.

Mechanism of the protective action of taurine in toxin and drug induced organ pathophysiology and diabetic complications: a review

Taurine (2-aminoethanesulfonic acid), a conditionally essential amino acid, is found in large concentrations in all mammalian tissues and is particularly abundant in aquatic foods. Taurine exhibits membrane stabilizing, osmoregulatory and cytoprotective effects, antioxidative properties, regulates intracellular Ca(2+) concentration, modulates ion movement and neurotransmitters, reduce the levels of pro-inflammatory cytokines in various organs and controls blood pressure. Recently, emerging evidence from the literature shows the effectiveness of taurine as a protective agent against several environmental toxins and drug-induced multiple organ injuries as the outcome of hepatotoxicity, nephrotoxicity, neurotoxicity, testicular toxicity and cardiotoxicity in several animal models. Besides, taurine is also effective in combating diabetes and its associated complications, including cardiomyopathy, nephropathy, neuropathy, retinopathy and atherosclerosis. These beneficial effects appear to be due to the multiple actions of taurine on cellular functions. This review summarizes the mechanism of the prophylactic role of taurine against several environmental toxins and drug-induced organ pathophysiology and diabetes.

Does conservative management really benefit patients with OAB?

The benefit that patients with overactive bladder (OAB) experience with conservative management is an important aspect in the evaluation of this therapy. The first-line options include behavioral interventions, and several techniques are available. Clinical research indicates amelioration of individual symptoms with these techniques, but few studies have shown a positive effect on health-related quality-of-life parameters. After failure of behavioral therapy or in combination with a training program, pharmacological therapy with anticholinergics is the next step. Extensive clinical research into different pharmacological compounds has shown significant effects on the symptomatic elements of OAB. The clinical relevance and the effects on quality-of-life parameters with pharmacological therapy have also been evaluated and show a significant effect on specific aspects. Recently, clinical research in conservative management of patients with OAB has focused more on evaluating patients' perceptions of their condition and the effects of treatment with patient-reported outcome instruments. Future studies should include these tools in the evaluation of any therapy in OAB.

Hypertension in a young boy: an energy drink effect

BACKGROUND

Use of energy drinks has significantly increased in recent times. Besides athletes, teenagers and students are among the most common consumers. However, popularity is also increasing among the younger and older age groups. Most of the users believe that they are a good source of instant energy and are unaware of its high Caffeine content resulting in harmful effects on health.

CASE PRESENTATION

We report the case of a young boy who presented with palpitations and high blood pressure as a result of energy drinks usage. He had been consuming a "Sting" energy drink on regular basis while studying for long hours during his O' level Exams. His medical examination revealed Sinus tachycardia and high blood pressure. Rest of the examination and lab workup was within normal limits. His pulse and blood pressure returned to normal range after discontinuing Sting usage.

CONCLUSION

Several studies have reported numerous health hazards including cardiac effects associated with energy drinks. Warning labeling should be done on these drinks regulating the content of Caffeine and its harmful effects on health.

The effects of energy beverages on cultured cells

The popularity and prevalence of energy beverages makes it essential to examine the interactions between the ingredients and their effects on the safety of these beverages. In this study, we used in vitro assays to examine the effects of two energy beverages on mesenchymal, epithelial and neuronal cells. Our results showed that treatment of epithelial and mesenchymal cells with either energy beverage resulted in a dose dependent delay in wound closure, in a scratch wound healing assay. In rat embryonic fibroblasts, treatment with the energy beverages led to decreased lamellipodia formation and decreased proliferation/viability; whereas in MDCK cells, energy beverage treatment resulted in actin disorganization without any effects on cell proliferation. This suggests that the mechanisms underlying delayed wound healing might be different in the two cell types. Interestingly, the delays in both cell types could not be mimicked by treatment of caffeine, taurine and glucose alone or in combinations. Furthermore, treatment of chick forebrain neuronal cultures with energy beverages resulted in a dose dependent inhibition of neurite outgrowth. The cellular assays used in this study provide a consistent, qualitative and quantitative system for examining the combinatorial effects of the various ingredients used in energy beverages.

Caffeine and urinary incontinence in US women

INTRODUCTION AND HYPOTHESIS

The goal of this study was to characterize associations between caffeine consumption and severity of urinary incontinence (UI) in US women. We hypothesized that moderate and high caffeine intake would be associated with UI in US women when controlling for other factors associated with UI.

METHODS

US women participated in the 2005-2006 and 2007-2008 National Health and Nutrition Examination Survey (NHANES), a cross-sectional, nationally representative survey. Using the Incontinence Severity Index, UI was categorized as "any" and "moderate/severe". Types of UI included stress, urge, mixed, and other. Food diaries were completed, and average water (grams/day), total dietary moisture (grams/day), and caffeine (milligrams/day) intake were calculated into quartiles. Stepwise logistic regression models were constructed adjusting for sociodemographics, chronic diseases, body mass index, self-rated health, depression, physical activity, alcohol use, dietary water and moisture intake, and reproductive factors.

RESULTS

From the 4,309 nonpregnant women (aged ≥20 years) who had complete UI and dietary data, UI prevalence for any UI was 41.0 % and 16.5 % for moderate/severe UI, with stress UI the most common type (36.6 %). Women consumed a mean caffeine intake of 126.7 mg/day. After adjusting for multiple factors, caffeine intake in the highest quartile (≥204 mg/day) was associated with any UI [prevalence odds ratio (POR) 1.47, 95 % confidence interval (CI) 1.07-2.01], but not moderate/severe UI (POR 1.42, 95 % CI 0.98-2.07). Type of UI (stress, urgency, mixed) was not associated with caffeine intake.

CONCLUSIONS

Caffeine intake ≥204 mg/day was associated with any UI but not with moderate/severe UI in US women.

A survey of energy drinks consumption practices among student -athletes in Ghana: lessons for developing health education intervention programmes

BACKGROUND

Globally, young adults and college athletes are primary targets of the marketing campaigns of energy drink companies. Consequently, it is reported that young adults and college athletes consume energy drinks frequently. The purpose of this study was to determine the prevalence of energy drink consumption among student-athletes selected from seven public universities in Ghana. The study assessed the energy drink consumption patterns, types usually consumed, frequency of consumption and reasons why athletes consumed energy drinks.

METHODS

A total number of 180 student-athletes gave their consent to participate in the study and completed a questionnaire which was administered during an inter-university sports competition.

RESULTS

Most of the participants (62.2%) reported consuming at least one can of energy drink in a week. A high proportion (53.6%) of the respondents who drink energy drinks indicated that they did so to replenish lost energy after training or a competition. Other reasons given as to why energy drinks were consumed by the study participants included to provide energy and fluids to the body (25.9%), to improve performance (9.8%) and to reduce fatigue (5.4%).

CONCLUSION

These results suggest the need to plan health education programmes to particularly correct some wrong perceptions that athletes have regarding the benefits of energy drinks and also create awareness among student-athletes about the side effects of excessive intake of energy drinks.

Methylxanthines and the kidney

This chapter describes the effects of the natural methylxanthines caffeine and theophylline on kidney function. Theophylline in particular was used traditionally to increase urine out put until more potent diuretics became available in the middle of the last century. The mildly diuretic actions of both methylxanthines are mainly the result of inhibition of tubular fluid reabsorption along the renal proximal tubule. Based upon the use of specific adenosine receptor antagonists and the observation of a complete loss of diuresis in mice with targeted deletion of the A1AR gene, transport inhibition by methylxanthines is mediated mainly by antagonism of adenosine A1 receptors (A1AR) in the proximal tubule. Methylxanthines are weak renal vasodilators, and they act as competitive antagonists against adenosine-induced preglomerular vasoconstriction. Caffeine and theophylline stimulate the secretion of renin by inhibition of adenosine receptors and removal of the general inhibitory brake function of endogenous adenosine. Since enhanced intrarenal adenosine levels lead to reduced glomerular filtration rate in several pathological conditions theophylline has been tested for its therapeutic potential in the renal impairment following administration of nephrotoxic substances such as radiocontrast media, cisplatin, calcineurin inhibitors or following ischemia-reperfusion injury. In experimental animals functional improvements have been observed in all of these conditions, but available clinical data in humans are insufficient to affirm a definite therapeutic efficacy of methylxanthines in the prevention of nephrotoxic or postischemic renal injury.

Energy beverages: content and safety

Exercise is making a resurgence in many countries, given its benefits for fitness as well as prevention of obesity. This trend has spawned many supplements that purport to aid performance, muscle growth, and recovery. Initially, sports drinks were developed to provide electrolyte and carbohydrate replacement. Subsequently, energy beverages (EBs) containing stimulants and additives have appeared in most gyms and grocery stores and are being used increasingly by "weekend warriors" and those seeking an edge in an endurance event. Long-term exposure to the various components of EBs may result in significant alterations in the cardiovascular system, and the safety of EBs has not been fully established. For this review, we searched the MEDLINE and EMBASE databases from 1976 through May 2010, using the following keywords: energy beverage, energy drink, power drink, exercise, caffeine, red bull, bitter orange, glucose, ginseng, guarana, and taurine. Evidence regarding the effects of EBs is summarized, and practical recommendations are made to help in answering the patient who asks, "Is it safe for me to drink an energy beverage when I exercise?"

Energy Drinks: An Assessment of Their Market Size, Consumer Demographics, Ingredient Profile, Functionality, and Regulations in the United States

  The consumption of energy drinks is rapidly increasing, as demonstrated by their large market growth. The targeted demographic group is teenagers, young adults, 18 to 34 y old; although expansion into nontraditional markets is also occurring. It is claimed that energy drinks can offer an increased energy boost related to their ingredient profile of caffeine, taurine, herbal extracts, and vitamins. Research suggests that energy drink formulations, in addition to increasing energy utilization, may also improve mood, enhance physical endurance, reduce mental fatigue, and increase reaction time. However, in most cases, the corresponding mechanisms of action are not clear. In addition, concerns have been raised over their safety and with a currently weak regulatory environment, efforts need to be made to ensure consumer safety. The objective of this article is to review the current U.S. energy drink market with emphasis on its market size, target demographic, active ingredients, potential benefits, safety, and regulations.

Practical aspects of lifestyle modifications and behavioural interventions in the treatment of overactive bladder and urgency urinary incontinence

Behavioural interventions are effective treatments for overactive bladder (OAB) and urgency urinary incontinence (UUI). They are in part aimed at improving symptoms with patient education on healthy bladder habits and lifestyle modifications, including the establishment of normal voiding intervals, elimination of bladder irritants from the diet, management of fluid intake, weight control, management of bowel regularity and smoking cessation. Behavioural interventions also include specific training techniques aimed at re-establishing normal voiding intervals and continence. Training techniques include bladder training, which includes a progressive voiding schedule together with relaxation and distraction for urgency suppression, and multicomponent behavioural training, which, in conjunction with pelvic floor muscle (PFM) exercises, includes PFM contraction to control urgency and increase the interval between voids. Guidelines for the conservative treatment of OAB and UUI have been published by several organisations and the physiological basis and evidence for the effectiveness of behavioural interventions, including lifestyle modifications, in the treatment of OAB and UUI have been described. However, many primary care clinicians may have a limited awareness of the evidence supporting the often straight-forward treatment recommendations and guidance for incorporating behavioural interventions into busy primary care practices, because most of this information has appeared in the specialty literature. The purpose of this review is to provide an overview of behavioural interventions for OAB and UUI that can be incorporated with minimal time and effort into the treatment armamentarium of all clinicians that care for patients with bladder problems. Practical supporting materials that will facilitate the use of these interventions in the clinic are included; these can be used to help patients understand lifestyle choices and voiding behaviours that may improve function in patients experiencing OAB symptoms and/or UUI as well as promote healthy bladder behaviours and perhaps even prevent future bladder problems. Interventions for stress urinary incontinence are beyond the scope of this review.

A survey of energy drink consumption patterns among college students

Background

Energy drink consumption has continued to gain in popularity since the 1997 debut of Red Bull, the current leader in the energy drink market. Although energy drinks are targeted to young adult consumers, there has been little research regarding energy drink consumption patterns among college students in the United States. The purpose of this study was to determine energy drink consumption patterns among college students, prevalence and frequency of energy drink use for six situations, namely for insufficient sleep, to increase energy (in general), while studying, driving long periods of time, drinking with alcohol while partying, and to treat a hangover, and prevalence of adverse side effects and energy drink use dose effects among college energy drink users.

Methods

Based on the responses from a 32 member college student focus group and a field test, a 19 item survey was used to assess energy drink consumption patterns of 496 randomly surveyed college students attending a state university in the Central Atlantic region of the United States.

Results

Fifty one percent of participants (n = 253) reported consuming greater than one energy drink each month in an average month for the current semester (defined as energy drink user). The majority of users consumed energy drinks for insufficient sleep (67%), to increase energy (65%), and to drink with alcohol while partying (54%). The majority of users consumed one energy drink to treat most situations although using three or more was a common practice to drink with alcohol while partying (49%). Weekly jolt and crash episodes were experienced by 29% of users, 22% reported ever having headaches, and 19% heart palpitations from consuming energy drinks. There was a significant dose effect only for jolt and crash episodes.

Conclusion

Using energy drinks is a popular practice among college students for a variety of situations. Although for the majority of situations assessed, users consumed one energy drink with a reported frequency of 1 – 4 days per month, many users consumed three or more when combining with alcohol while partying. Further, side effects from consuming energy drinks are fairly common, and a significant dose effect was found with jolt and crash episodes. Future research should identify if college students recognize the amounts of caffeine that are present in the wide variety of caffeine-containing products that they are consuming, the amounts of caffeine that they are consuming in various situations, and the physical side effects associated with caffeine consumption.

Caffeine, fluid-electrolyte balance, temperature regulation, and exercise-heat tolerance

Dietitians, exercise physiologists, athletic trainers, and other sports medicine personnel commonly recommend that exercising adults and athletes refrain from caffeine use because it is a diuretic, and it may exacerbate dehydration and hyperthermia. This review, contrary to popular beliefs, proposes that caffeine consumption does not result in the following: (a) water-electrolyte imbalances or hyperthermia and (b) reduced exercise-heat tolerance.