Influence of energy drink ingredients on mood and cognitive performance

Effects of Acute Guarana (Paullinia cupana) Ingestion on Mental Performance and Vagal Modulation Compared to a Low Dose of Caffeine

Guarana (GUA), a Brazilian seed extract, contains caffeine and other bioactive compounds that may have psychoactive effects. To assess the acute effects of GUA compared to a low dose of caffeine (CAF) on cognitive and mood parameters, twenty participants completed a double-blind, crossover experiment where they ingested capsules containing the following: (1) 100 mg CAF, (2) 500 mg GUA containing 130 mg caffeine, or (3) placebo (PLA). Cognitive tests (Simon and 2N-Back Task) were performed at the baseline (pre-ingestion) and 60 min after ingestion. The response time for the cognitive tests and heart rate variability were unaffected (p > 0.05) by treatment, although 2N-Back was overall faster (p = 0.001) across time. The accuracy in the 2N-Back Task showed a significant interaction effect (p = 0.029) due to higher post-ingestion versus pre-ingestion levels (p = 0.033), but only with the PLA. The supplements also had no effect on cognitive measures following physical fatigue (n = 11). There was an interaction effect on perceived mental energy, where the pre-ingestion of GUA had lower mental pep ratings compared to post-ingestion (p = 0.006) and post-exercise (p = 0.018) levels. Neither the acute ingestion of GUA nor low dose of CAF influenced cognitive performance or provided consistent benefit on mood or mental workload through vagal modulation. Additional investigations are beneficial to determining the lowest effective dose for CAF or GUA to influence mood and/or cognitive performance.

Nootropic supplements for esports

Background: esports, or organized video game competitions, have been expanding quickly. The use of dietary supplements by esports players appears vulgarized but lacks supporting evidence. Objectives: To outline studies that tested the effects of dietary supplements on video gaming, summarize their findings, highlight knowledge gaps, and recommend future research. Eligibility criteria: Clinical trials published in English between 1990 and 2023 that assessed the effects of dietary supplements on the cognitive performance of video gamers. Sources of evidence: The Web of Science, PubMed, Scopus, and Google Scholar databases. Charting methods: PRISMA's (2020) flow diagram was used to create the data chart. Results: Sixteen studies were outlined. Thirteen were randomized, thirteen applied acute interventions, ten applied a crossover design and only three weren't placebo-controlled. Of the 10 studies that included caffeine (40-200 mg), four reported significant positive effects on cognition (attention, processing speed, working memory), two on first-person shooter video gaming performance (reaction time, hit accuracy, time to hit 60 targets), and one on Tetris game score. All 3 studies that included arginine silicate (1500 mg) reported significant improvements in one or more aspects of cognition (reaction time, attention, visual representation, and spatial planning). Two studies that tested sucrose (21 and 26.8 g) didn't report significant improvements, while one study that tested 26.1 g of glucose registered significant positive effects on processing speed and sustained attention. Conclusions: The published literature has focused on the effects of caffeine, which may exert both positive and negative effects on esports players. Additional, high-quality research is needed.

Novel Energy Drink Improves Cognitive Function and Mood, without Influencing Myocardial Oxygen Demand or Ventricular Repolarization in Adult Gamers: A Randomized, Double-Blind, Placebo-Controlled, Crossover Trial

OBJECTIVES

To examine the efficacy of acute consumption of a novel energy drink (C4S) versus placebo for improving cognitive and gaming performance and mood. Secondarily, we examined the cardiovascular safety profile of acute C4S consumption.

METHODS

Forty-five healthy, young adult video gamers completed two experimental visits in randomized order where they consumed either C4S or a placebo and then completed a validated battery of neurocognitive tests, played five video games, and completed a mood state survey. Blood pressure (BP), heart rate (HR), oxygen saturation, and electrocardiogram measurements were taken at baseline and repeated throughout each visit.

RESULTS

Acute consumption of C4S improved cognitive flexibility (absolute mean or median difference [95% CI] = +4.3 [2.2-6.4]; p < 0.001; d = 0.63), executive function (+4.3 [2.3-6.3]; p < 0.001; d = 0.63), sustained attention (+2.1 [0.6-3.6]; p = 0.01; d = 0.44), motor speed (+2.9 [0.8-4.9]; p < 0.001; d = 0.44), psychomotor speed (+3.9 [0.1-7.7]; p = 0.04; d = 0.32) working memory (+1.0 [0.1-1.9]; p = 0.02; d = 0.35), and performance in the two-dimensional visuospatial game Tetris (+463 [-419-2,065] pts; p = 0.049; d = 0.30) compared to placebo. C4S also improved Fatigue-Inertia (-1 [-3-0]; p = 0.004; d = 0.45), Vigor-Activity (+2.4 [1.3-3.6]; p < 0.001; d = 0.64), Friendliness (+0 [0-1]; p = 0.04; d = 0.32), and Total Mood Disturbance (-3 [-6-0]; p = 0.002; d = 0.44). BP increased slightly in C4S versus placebo, while HR decreased from baseline to post-drink in the C4S condition. Rate-pressure-product was higher in C4S versus placebo independent of time but did not increase from baseline. There was no effect on corrected QT interval.

CONCLUSION

Acute consumption of C4S was efficacious for cognitive performance, visuospatial gaming performance, and mood enhancement, and had no effect on myocardial oxygen demand or ventricular repolarization, despite being associated with increases in BP.

Acute Effects of Energy Drink on Autonomic and Cardiovascular Parameters Recovery in Individuals with Different Cardiorespiratory Fitness: A Randomized, Crossover, Double-Blind and Placebo-Controlled Trial

Fundamento

Tem-se sugerido que o consumo de bebidas energéticas (BEs) possa afetar a atividade cardiovascular.

Objetivos

Investigar os efeitos agudos da ingestão de BE sobre a variabilidade da frequência cardíaca (VFC) recuperação cardiovascular após exercício aeróbico moderado em homens de diferentes capacidades cardiorrespiratórias.

Métodos

Este é um estudo randomizado, duplo cego, crossover, controlado por placebo. Vinte e oito jovens adultos foram divididos em dois grupos de acordo com o pico de consumo de oxigênio (pico de VO2): (1) pico de VO2 alto (AO) – pico de VO2 > 52,15 mL/Kg/min, e (2) pico de VO2 baixo (BO) - pico de VO2 <52,15 mL/Kg/min. Os indivíduos de ambos os grupos foram submetidos a dois protocolos de exercícios em ordem aleatória: exercício moderado aeróbico (60% de pico de VO2) após a ingestão de 250 mL de água (protocolo placebo) ou 250 mL de BE (protocolo BE). Durante os testes de exercício, foram registrados valores de parâmetros cardiorrespiratórios e de VFC.

Resultados

Foram observadas diferenças significativas para o índice de LF (unidades normalizadas) entre “repouso” e “Rec1” nos grupos de AO e BO durante o protocolo BE. Para a razão LF/HF, foram observadas diferenças significativas entre “repouso” e Rec1 nos grupos AO e BO nos protocolos BE.

Conclusão

A ingestão aguda de BE retardou a recuperação da frequência cardíaca após o exercício em indivíduos com capacidade cardiorrespiratória baixa e indivíduos com capacidade cardiorrespiratória alta.

Self-Reported Emotions and Facial Expressions on Consumer Acceptability: A Study Using Energy Drinks

Emotional responses elicited by foods are of great interest for new product developers and marketing professionals, as consumer acceptance proved to be linked to the emotions generated by the product in the consumers. An emotional measurement is generally considered an appropriate tool to differentiate between the products of similar nutritional value, flavour, liking and packaging. Novel methods used to measure emotions include self-reporting verbal and visual measurements, and facial expression techniques. This study aimed to evaluate the explicit and implicit emotional response elicited during the tasting of two different brands (A and B) of energy drinks. The explicit response of consumers was assessed using liking (nine-point hedonic scale), and emotions (EsSense Profile^®—Check-All-That-Apply questionnaire), and implicit emotional responses were evaluated by studying facial expressions using the Affectiva Affdex^® software. The familiarity of the product and purchase intent were also assessed during the study. The hedonic rating shows a significant difference in liking between the two brands of energy drink during the tasting session. For the explicit emotional responses, participants elicited more positive emotions than the negative emotions for both energy drinks. However, participants expressed “happy”, “active” and “eager” emotions more frequently for energy drink A. On the other hand, the implicit emotional responses through facial expressions indicated a high level of involvement of the participants with energy drink B as compared to energy drink A. The study showed that overall liking and the explicit and implicit emotional measurements are weakly to moderately correlated.

Can Functional Beverages Serve as a Substantial Source of Macroelements and Microelements in Human Nutrition?-Analysis of Selected Minerals in Energy and Isotonic Drinks

Studies on the ingredients of energy drinks and isotonic drinks focus mainly on the evaluation of their content in terms of substances modulating the body's metabolism or those regarded as food additives. Having regard to the widespread availability of these beverages, their diversity and the limited number of studies in this area, the aim of this study was to analyse the contents of F, Al, Cd, Cr, Mn, V, Co, Ni, Zn, Bi and Na in the energy drinks and isotonic drinks available in the Polish market. Fluorine concentration was analysed using an ion-selective electrode. The other elements were analysed using ICP-OES. Obtained results showed that functional beverages need to be taken into account as a source of macroelements and microelements in human nutrition, particularly when ingested often and in large quantities (which applies particularly to the young population). Moreover, due caution needs to be maintained in consumer choices.

Investigating associations between caffeinated beverage consumption and later alcohol consumption among early adolescents

Previous research has demonstrated that caffeinated beverage consumption predicts alcohol consumption among early adolescents. This study aimed to investigate this association in two ways: (1) by examining if this association remained significant once other established risk factors for alcohol were adjusted for statistically; and (2) by considering three possible moderators of this association: gender, sensation-seeking, and parental monitoring. Data from the Camden Youth Development Study, a longitudinal, community-based study of middle-school students, were used. Youth were initially assessed in 6th and 7th grade and followed-up 16 months later. Self-reports of frequency of energy drink, coffee, and alcohol consumption, as well as sensation-seeking, perceived peer and best friend alcohol use, alcohol expectancies, and parental monitoring, were used. Results indicated that both energy drink and coffee consumption predicted later alcohol consumption, even after adjusting for other risk factors for alcohol consumption. Parental monitoring was a significant moderator of this link, such that youth who consumed energy drinks and reported low parental monitoring were particularly at risk for later alcohol consumption. These findings indicate that the link between earlier caffeine consumption and later alcohol consumption is not simply due to the co-occurrence of caffeine consumption with other risk factors for alcohol use. In addition, risk associated with early energy drink consumption appears to be particularly pronounced for youth in families characterized by low parental monitoring.

Energy drinks, caffeine, junk food, breakfast, depression and academic attainment of secondary school students

BACKGROUND

Energy drinks are widely consumed, and concerns have been raised about possible negative outcomes.

AIMS

The aim of the present research was to examine associations between consumption of energy drinks, caffeine and junk food, and academic attainment in a sample of UK secondary school students.

METHODS

A total of 3071 students agreed to participate in the study; 2677 completed the survey on one occasion (52.4% female, 47.6% male; approximately 20% of the sample from each school year) and 1660 (49.6% female, 50.4% male) completed the survey a second time, approximately six months later. The academic attainment measure was based on Key Stage 3 and Key Stage 4 grades for Maths and English.

RESULTS

In the cross-sectional analyses, logistic regressions showed that consumption of energy drinks was associated with a greater likelihood of being in the low academic achievement group. This was not found for other sources of caffeine. The effect of energy drinks was still significant when demographic, academic and health/lifestyle variables were covaried. However, inclusion of an unhealthy diet variable (junk food) removed the significant effect of energy drinks. Similar observations were made in the longitudinal study, with the poorer attainment of those who consumed energy drinks reflecting breakfast omission and depression.

DISCUSSION

The present findings indicate that consumption of energy drinks is associated with an increased likelihood of poor academic attainment that reflects energy drink consumption being part of an unhealthy diet or being associated with skipping breakfast rather than a more specific effect, such as being a source of caffeine. Although the current study extends previous research by utilising a longitudinal design, intervention studies are now required to better answer questions relating to causality and direction of effect.

Perinatal exposure to energy drink induces oxidative damage in the liver, kidney and brain, and behavioral alterations in mice offspring

The worldwide consumption of energy drinks (EDs) has increased in recent years. EDs have several side effects and can be linked to liver injury, kidney damage and risk-seeking behavior. The impact of perinatal consumption of EDs on the newborns has not been previously investigated. In this study, we evaluated the effects of perinatal exposure to a caffeinated ED on the liver, kidney, brain, locomotor activity and anxiety in mice newborns. Pregnant mice received 2.5 or 5 ml ED by oral gavage from the first day of pregnancy until day 15 after birth. Perinatal exposure to the ED induced a significant increase in lipid peroxidation and declined antioxidant defenses in the liver, kidney, cerebrum, cerebellum and medulla oblongata of the newborns at days 21 and 35 after birth. ED induced several histological alterations, including vacuolations and lipid infiltration of hepatocytes, developing and degenerated glomeruli and dilated urinary spaces in the renal cortex, pyknosis and chromatolysis of the cerebral and medullary neurons, and degenerated and abnormal Purkinje cells in the cerebellum. In addition, ED increased the locomotion and induced anxiety-like behavior in mice newborns. In conclusion, perinatal exposure to EDs induces oxidative stress, tissue injury and behavioral alterations in the mice newborns. Therefore, the consumption of EDs during pregnancy and lactation has a negative impact on the newborns and should be treated as a significant health problem that warrants attention.

A caffeine-maltodextrin mouth rinse counters mental fatigue

INTRODUCTION

Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity that has negative implications on many aspects in daily life. Caffeine and carbohydrate ingestion have been shown to be able to reduce these negative effects of mental fatigue. Intake of these substances might however be less desirable in some situations (e.g., restricted caloric intake, Ramadan). Rinsing caffeine or glucose within the mouth has already been shown to improve exercise performance. Therefore, we sought to evaluate the effect of frequent caffeine-maltodextrin (CAF-MALT) mouth rinsing on mental fatigue induced by a prolonged cognitive task.

METHODS

Ten males (age 23 ± 2 years, physical activity 7.3 ± 4.3 h/week, low CAF users) performed two trials. Participants first completed a Flanker task (3 min), then performed a 90-min mentally fatiguing task (Stroop task), followed by another Flanker task. Before the start and after each 12.5% of the Stroop task (eight blocks), subjects received a CAF-MALT mouth rinse (MR: 0.3 g/25 ml CAF: 1.6g/25 ml MALT) or placebo (PLAC: 25 ml artificial saliva).

RESULTS

Self-reported mental fatigue was lower in MR (p = 0.017) compared to PLAC. Normalized accuracy (accuracy first block = 100%) was higher in the last block of the Stroop in MR (p = 0.032) compared to PLAC. P2 amplitude in the dorsolateral prefrontal cortex (DLPFC) decreased over time only in PLAC (p = 0.017).

CONCLUSION

Frequent mouth rinsing during a prolonged and demanding cognitive task reduces mental fatigue compared to mouth rinsing with artificial saliva.

Cognitive and Mood Effects of a Nutrient Enriched Breakfast Bar in Healthy Adults: A Randomised, Double-Blind, Placebo-Controlled, Parallel Groups Study

Objectives: Few previous studies have assessed the effects of concomitant administration of multiple potentially psychoactive nutrients. Methods: 95 healthy adult participants consumed either a nutrient enriched breakfast bar (containing α-Linolenic acid, l-tyrosine, l-theanine, vitamins, minerals and 21.5 mg of caffeine) or an isocaloric, macronutrient matched control bar for 56 days. Cognitive function and mood were assessed pre-dose and at 40- and 160-min post-dose on the 1st and 56th day of the intervention period. Results: The results demonstrated acute effects of treatment across post-dose assessments on both assessment days in terms of alertness, and on tasks assessing attention, working and episodic memory and executive function, including cognitively demanding Serial subtraction and Rapid Visual Information Processing tasks. There were no evident chronic effects independent of the breakfast bars’ acute effects. Discussion: These results demonstrate that a nutrient enriched breakfast bar with low caffeine content can exert striking beneficial effects on acute cognitive function and alertness.

High stress, lack of sleep, low school performance, and suicide attempts are associated with high energy drink intake in adolescents

Objective

Although an association between energy drinks and suicide has been suggested, few prior studies have considered the role of emotional factors including stress, sleep, and school performance in adolescents. This study aimed to evaluate the association of energy drinks with suicide, independent of possible confounders including stress, sleep, and school performance.

Methods

In total, 121,106 adolescents with 13–18 years olds from the 2014 and 2015 Korea Youth Risk Behavior Web-based Survey were surveyed for age, sex, region of residence, economic level, paternal and maternal education level, sleep time, stress level, school performance, frequency of energy drink intake, and suicide attempts. Subjective stress levels were classified into severe, moderate, mild, a little, and no stress. Sleep time was divided into 6 groups: < 6 h; 6 ≤ h < 7; 7 ≤ h < 8; 8 ≤ h < 9; and ≥ 9 h. School performance was classified into 5 levels: A (highest), B (middle, high), C (middle), D (middle, low), and E (lowest). Frequency of energy drink consumption was divided into 3 groups: ≥ 3, 1–2, and 0 times a week. The associations of sleep time, stress level, and school performance with suicide attempts and the frequency of energy drink intake were analyzed using multiple and ordinal logistic regression analysis, respectively, with complex sampling. The relationship between frequency of energy drink intake and suicide attempts was analyzed using multiple logistic regression analysis with complex sampling.

Results

Higher stress levels, lack of sleep, and low school performance were significantly associated with suicide attempts (each P < 0.001). These variables of high stress level, abnormal sleep time, and low school performance were also proportionally related with higher energy drink intake (P < 0.001). Frequent energy drink intake was significantly associated with suicide attempts in multiple logistic regression analyses (AOR for frequency of energy intake ≥ 3 times a week = 3.03, 95% CI = 2.64–3.49, P < 0.001).

Conclusion

Severe stress, inadequate sleep, and low school performance were related with more energy drink intake and suicide attempts in Korean adolescents. Frequent energy drink intake was positively related with suicide attempts, even after adjusting for stress, sleep time, and school performance.

Cocaine and Caffeine Effects on the Conditioned Place Preference Test: Concomitant Changes on Early Genes within the Mouse Prefrontal Cortex and Nucleus Accumbens

Caffeine is the world's most popular psychostimulant and is frequently used as an active adulterant in many illicit drugs including cocaine. Previous studies have shown that caffeine can potentiate the stimulant effects of cocaine and cocaine-induced drug seeking behavior. However, little is known about the effects of this drug combination on reward-related learning, a key process in the maintenance of addiction and vulnerability to relapse. The goal of the present study was thus to determine caffeine and cocaine combined effects on the Conditioned Place Preference (CPP) test and to determine potential differential mRNA expression in the Nucleus Accumbens (NAc) and medial prefrontal cortex (mPFC) of immediate-early genes (IEGs) as well as dopamine and adenosine receptor subunits. Mice were treated with caffeine (5 mg/kg, CAF), cocaine (10 mg/kg, COC), or their combination (caffeine 5 mg/kg + cocaine 10 mg/kg, CAF-COC) and trained in the CPP test or treated with repeated injections inside the home cage. NAc and mPFC tissues were dissected immediately after the CPP test, after a single conditioning session or following psychostimulant injection in the home cage for mRNA expression analysis. CAF-COC induced a marked change of preference to the drug conditioned side of the CPP and a significant increase in locomotion compared to COC. Gene expression analysis after CPP test revealed specific up-regulation in the CAF-COC group of Drd1a, cFos, and FosB in the NAc, and cFos, Egr1, and Npas4 in the mPFC. Importantly, none of these changes were observed when animals received same treatments in their home cage. With a single conditioning session, we found similar effects in both CAF and CAF-COC groups: increased Drd1a and decreased cFos in the NAc, and increased expression of Drd1a and Drd2, in the mPFC. Interestingly, we found that cFos and Npas4 gene expression were increased only in the mPFC of the CAF-COC. Our study provides evidence that caffeine acting as an adulterant could potentiate reward-associated memories elicited by cocaine. This is associated with specific changes in IEGs expression that were observed almost exclusively in mice that received the combination of both psychostimulants in the context of CPP memory encoding and retrieval. Our results highlight the potential relevance of caffeine in the maintenance of cocaine addiction which might be mediated by modifying neural plasticity mechanisms that strengthen learning of the association between drug and environment.

Acute effects of caffeine-containing energy drinks on physical performance: a systematic review and meta-analysis

PURPOSE

Caffeine-containing energy drinks (EDs) are currently used as ergogenic aids to improve physical performance in a wide variety of sport disciplines. However, the outcomes of previous investigations on this topic are inconclusive due to methodological differences, especially, in the dosage of the active ingredients and the test used to assess performance.

METHODS

We performed a systematic review and meta-analysis of published studies to evaluate the effects of acute ED intake on physical performance. The search for references was conducted in the databases PubMed, ISI Web of Knowledge and SPORTDiscus until December 2015.

RESULTS

Thirty-four studies published between 1998 and 2015 were included in the analysis. Using a random-effects model, effect sizes (ES) were calculated as the standardized mean difference. Overall, ED ingestion improved physical performance in muscle strength and endurance (ES = 0.49; p < 0.001), endurance exercise tests (ES = 0.53; p < 0.001), jumping (ES = 0.29; p = 0.01) and sport-specific actions (ES = 0.51; p < 0.001), but not in sprinting (ES = 0.14; p = 0.06). The meta-regression demonstrated a significant association between taurine dosage (mg) and performance (slope = 0.0001; p = 0.04), but not between caffeine dosage (mg) and performance (slope = 0.0009; p = 0.21).

CONCLUSION

ED ingestion improved performance in muscle strength and endurance, endurance exercise tests, jumping and sport-specific actions. However, the improvement in performance was associated with taurine dosage.

Inaccurate or delayed diagnosis of hollow organ perforation by emergency physicians: using a qualitative approach to identify the causes

BACKGROUND

Mistakes or delays in the diagnosis of hollow organ perforation may be detrimental to prognosis. Nonetheless, emergency physicians (EPs) are prone to misdiagnosing this condition in specific scenarios. The factors leading to errors in their cognitive processes, however, have received little attention.

METHODS

Using a qualitative approach, we conducted in-depth semi-structured interviews with EPs in the emergency departments (EDs) of three hospitals in Taiwan. We purposively selected participants to obtain a sample that can contribute essential information about the diagnostic process. Sampling continued until new information was no longer being gathered. All interviews were audio-recorded, transcribed verbatim, and then analyzed by two investigators according to grounded theory.

RESULTS

Based on 23 cases from 20 EPs, four themes emerged from the analysis regarding the reasons for diagnostic errors: (1) atypical disease presentations (6/23; 26%), (2) cognitive process of the physicians (21/23; 91%), (3) systemic factors (14/23; 61%), and (4) composite factors (14/23; 61%).

CONCLUSIONS

These findings provide valuable insight into the factors that contribute to diagnostic error in cases of abdominal hollow organ perforation. The results offer a basis on which to build a framework for teaching physicians how to avoid misdiagnosing hollow organ perforation in the future.

Energy Drink and Coffee Consumption and Psychopathology Symptoms Among Early Adolescents: Cross-Sectional and Longitudinal Associations

Background: Little is known about possible links between energy drink use and psychopathology among youth. This study examined cross-sectional and longitudinal associations between energy drink consumption and psychopathology among early adolescents. In addition, associations between psychopathology and coffee consumption were examined to assess whether findings were specific to energy drinks or also applied to another commonly used caffeinated beverage. Methods: One hundred forty-four youth who participated in the Camden Youth Development Study (72 males; mean age 11.9 at wave 1; 65% Hispanic, 30% African American) were assessed using self-report measures of frequency of energy drink and coffee consumption and depression, anxiety, conduct disorder (CD) symptoms, and teacher reports of attention-deficit hyperactivity disorder (ADHD). Youth (92%) were reassessed 16 months later. Results: Concurrently, energy drink and coffee consumption were associated with similar psychopathology symptoms; when the other beverage was adjusted for, energy drinks remained associated with CD and coffee remained associated with panic anxiety. Initial energy drink consumption predicted increasing ADHD and CD over time, though the association with CD dropped to a trend level of significance when coffee was adjusted for. Initial levels of hyperactive ADHD predicted increasing coffee consumption over time; this association remained when energy drinks were controlled. Social anxiety was associated with less increase in energy drink consumption over time, controlling for coffee. Conclusion: Energy drink and coffee consumption among early adolescents are concurrently associated with similar psychopathology symptoms. Longitudinally, the associations between these beverages and psychopathology differ, indicating that these substances have differing implications for development over time.

Subjective Responses to Caffeine Are Influenced by Caffeine Dose, Sex, and Pubertal Stage

Background: Our previous work has shown that there are sex differences in subjective responses to acute caffeine administration in adolescents. The purpose of this study was to determine if these sex differences are dependent on pubertal development. Materials and Methods: We examined subjective responses before and after administration of 0, 1, and 2 mg/kg of caffeine in pre- and postpubertal boys and girls (n = 112). In addition, we examined differences in subjective responses to acute caffeine in both the luteal and follicular phases of the menstrual cycle in postpubertal girls. Results: Caffeine at both doses resulted in greater changes in responses on the Addiction Research Center Inventory and the Brief Assessment of Mood States compared with placebo. Girls reported greater increases from baseline to peak in feeling different and liking the feeling than boys after 2 mg/kg of caffeine regardless of pubertal stage. Postpubertal girls also had a greater decrease from baseline in reports of feeling high and greater increases from baseline in reports of wanting more than postpubertal males. Finally, girls had greater changes (both increases and decreases) in responses on the Brief Mood Questionnaire when in the follicular phase compared with the luteal phase. This was also true for reports of feeling high and feeling different on the Drug Effects Questionnaire. None of these effects varied as a function of usual caffeine use, suggesting that differences are not the result of tolerance or sensitization. Conclusions: These results suggest that subjective responses to caffeine emerge before puberty, but sex differences may be strengthened after pubertal development.

Executive summary of NIH workshop on the Use and Biology of Energy Drinks: Current Knowledge and Critical Gaps

Sales of energy drinks in the United States reached $12.5 billion in 2012. Emergency department visits related to consumption of these products have increased sharply, and while these numbers remain small relative to product sales, they raise important questions regarding biological and behavioral effects. Although some common ingredients of energy drinks have been extensively studied (e.g., caffeine, B vitamins, sugars, inositol), data on other ingredients (e.g., taurine) are limited. Summarized here are data presented elsewhere in this issue on the prevalence and patterns of caffeine-containing energy drink use, the effects of these products on alertness, fatigue, cognitive functions, sleep, mood, homeostasis, as well as on exercise physiology and metabolism, and the biological mechanisms mediating the observed effects. There are substantial data on the effects of some energy drink ingredients, such as caffeine and sugars, on many of these outcomes; however, even for these ingredients many controversies and gaps remain, and data on other ingredients in caffeine-containing energy drinks, and on ingredient interactions, are sparse. This summary concludes with a discussion of critical gaps in the data and potential next steps.

The blood pressure-elevating effect of Red Bull energy drink is mimicked by caffeine but through different hemodynamic pathways

The energy drink Red Bull (RB) has recently been shown to elevate resting blood pressure (BP) and double product (reflecting increased myocardial load). However, the extent to which these effects can be explained by the drink's caffeine and sugar content remains to be determined. We compared the cardiovascular impact of RB to those of a comparable amount of caffeine, and its sugar-free version in eight young healthy men. Participants attended four experimental sessions on separate days according to a placebo-controlled randomized crossover study design. Beat-to-beat hemodynamic measurements were made continuously for 30 min at baseline and for 2 h following ingestion of 355 mL of either (1) RB + placebo; (2) sugar-free RB + placebo; (3) water + 120 mg caffeine, or (4) water + placebo. RB, sugar-free RB, and water + caffeine increased BP equally (3-4 mmHg) in comparison to water + placebo (P < 0.001). RB increased heart rate, stroke volume, cardiac output, double product, and cardiac contractility, but decreased total peripheral resistance (TPR) (all P < 0.01), with no such changes observed following the other interventions. Conversely, sugar-free RB and water + caffeine both increased TPR in comparison to the water + placebo control (P < 0.05). While the impact of RB on BP is the same as that of a comparable quantity of caffeine, the increase occurs through different hemodynamic pathways with RB's effects primarily on cardiac parameters, while caffeine elicits primarily vascular effects. Additionally, the auxiliary components of RB (taurine, glucuronolactone, and B-group vitamins) do not appear to influence these pathways.