Search

This review aimed to conduct a meta-analysis of studies examining the effects of caffeine on rate of force development (RFD). Ten databases were searched to find relevant studies. Risk of bias (RoB) of the included studies was evaluated. Data were analyzed in a random-effects meta-analysis. Eleven studies with “some concerns” regarding RoB were included. In the main meta-analysis, there was a significant ergogenic effect of caffeine ingestion on RFD (Hedges’ g = 0.37 ; 95% confidence interval [CI]: 0.21, 0.52 ; p < 0.0001). An ergogenic effect of caffeine was also found on RFD during resistance exercises (Hedges’ g = 0.49 ; 95% CI: 0.30, 0.67 ; p < 0.0001), but not during the countermovement jump test (Hedges’ g = 0.18 ; 95% CI: –0.02, 0.39 ; p = 0.08), with a significant difference between the subgroups (p = 0.03). Small-to-moderate (3–5 mg/kg ; Hedges’ g = 0.25 ; 95% CI: 0.09, 0.41 ; p = 0.002) and moderate-to-high caffeine doses (6–10 mg/kg) enhanced RFD (Hedges’ g = 0.57 ; 95% CI: 0.30, 0.85 ; p < 0.0001), even though the effects were larger with higher caffeine doses (p = 0.04). Overall, caffeine ingestion increases RFD, which is relevant given that RFD is commonly associated with sport-specific tasks. From a practical perspective: (1) individuals interested in the acute enhancement of RFD in resistance exercise may consider supplementing with caffeine ; and (2) given that evaluation of RFD is most commonly used for testing purposes, caffeine ingestion (3–10 mg/kg 60 min before exercise) should be standardized before RFD assessments.

Purpose The main goal of this study was to evaluate the effectiveness of two different doses of caffeine (3 and 6 mg/kg) to enhance bar velocity during the bench press in women habituated to caffeine. Methods Twelve recreationally trained women (age: 23.3 ± 0.8 years, body mass: 60.7 ± 5.7 kg, bench press one-repetition maximum (1RM): 44.3 ± 7.8 kg, daily caffeine ingestion: 5.7 ± 2.0 mg/kg/day) participated in a randomized double-blind experimental design. Each participant performed four different experimental sessions: after no supplementation (control, CON), after ingesting 3 and 6 mg/kg of caffeine (CAF-3 and CAF-6, respectively), or after ingesting a placebo (PLAC). In each experimental session, the participants performed 3 sets of 3 repetitions of the bench press exercise at 50% 1RM. Results A two-way repeated-measures ANOVA with subsequent post hoc analyses indicated significant increases in peak velocity (p p Conclusion These results suggest that 6 mg/kg of caffeine can be an effective dose to improve power-specific training outcomes in women habituated to caffeine. However, the ergogenic effect of 6 mg/kg of caffeine may be derived from a combination of biological effects and expectancy, as this dose was only superior to the control condition with no differences over the placebo.

Summary Objective The purpose of this study is to examine differences in visual and audial reaction times after the consumption of various doses of caffeine. Methods By means of a double-blind experimental design, changes in reaction times were observed with regard to various caffeine doses (100 mg or ∼ 3 mg·kg− 1) and different times from consumption (30 min or 60 min). The research sample consisted of 28 (15 men, 22.2 ± 0.8 years old; 13 women, 22.6 ± 1.7 years old) sports active students. The levels of simple and choice reaction times on visual stimuli and audial reaction times were monitored. Results The results showed a significant decrease in audial reaction time after 30 min and 60 min, and in choice reaction time after 60 min in the case of 100 mg of caffeine consumption. Furthermore, the influence of a higher dose (∼ 3 mg·kg− 1) of caffeine was also apparent. Conclusion Based on these results, it is possible to conclude that increasing amounts of caffeine can cause a decrease in visual and audial reaction times. These results may be useful in everyday human activities (extensive time driving a car) as well as being useful to sports coaches in preparation for sports where both audial and visual reaction times play an important role in overall sport performance (swimming, athletics, combat sports).

Although caffeine is a widely used ergogenic resource, some information regarding its effects on resistance exercises is still lacking. The objective of the present study was to verify the acute effect of the ingestion of two different doses of caffeine on performance during a session of resistance exercises and to analyze the perception of the subjects in relation to the intake of caffeine. Following a double-blind, randomised, cross-over, controlled, and non-placebo design, 14 trained and healthy men (24.7 ± 6.8 years; 79.8 ± 9.8 kg; 177.3 ± 8.5 cm) performed a training session in chest-press, shoulder-press, and biceps curl exercises (3 sets until exhaustion; 70% 1RM; 3 min rest interval; 2 s for each concentric and eccentric phase) on three non-consecutive days after ingestion of 3 mg.kg

To determine whether intermittent hypoxia (IH) persisting after 36 weeks postmenstrual age (PMA) can be attenuated using caffeine doses sufficient to maintain caffeine concentrations >20 μg ml−1. Twenty-seven infants born 20 μg ml−1 on study caffeine doses. IH was significantly attenuated through 38 weeks PMA compared with the control group. Caffeine doses of 14 to 20 mg kg−1 day−1 were sufficient to maintain caffeine concentrations >20 μg ml−1 and reduce IH in preterm infants at 36 to 38 weeks PMA.

The objectives of this study were to estimate the impact of\ud chewing time on caffeine release from gum and to understand\ud caffeine pharmacokinetics. Caffeine release increased with\ud chewing time (2 min < 5 min < 10 min). Furthermore, two plasma\ud caffeine concentration peaks were observed suggesting that\ud caffeine absorption occurs both through the oral mucosa and\ud gastrointestinal tract. This is of practical relevance to maximise\ud caffeine doses and to synchronise effort with peak caffeine\ud concentration.

Purpose: To explore the effects of 3 doses of caffeine on muscle strength and muscle endurance. Methods: Twenty-eight resistance-trained men completed the testing sessions under 5 conditions: no-placebo control, placebo control, and with caffeine doses of 2, 4, and 6 mg·kg−1. Muscle strength was assessed using the 1-repetition-maximum test; muscle endurance was assessed by having the participants perform a maximal number of repetitions with 60% 1-repetition maximum. Results: In comparison with both control conditions, only a caffeine dose of 2 mg·kg−1 enhanced lower-body strength (d = 0.13–0.15). In comparison with the no-placebo control condition, caffeine doses of 4 and 6 mg·kg−1 enhanced upper-body strength (d = 0.07–0.09) with a significant linear trend for the effectiveness of different doses of caffeine (P = .020). Compared with both control conditions, all 3 caffeine doses enhanced lower-body muscle endurance (d = 0.46–0.68). For upper-body muscle endurance, this study did not find significant effects of caffeine. Conclusions: This study revealed a linear trend between the dose of caffeine and its effects on upper-body strength. The study found no clear association between the dose of caffeine and the magnitude of its ergogenic effects on lower-body strength and muscle endurance. From a practical standpoint, the magnitude of caffeine’s effects on strength is of questionable relevance. A low dose of caffeine (2 mg·kg−1)—for an 80-kg individual, the dose of caffeine in 1–2 cups of coffee—may produce substantial improvements in lower-body muscle endurance with the magnitude of the effect being similar to that attained using higher doses of caffeine.

In 2016–2017, we conducted and published a systematic review on caffeine safety [1] that set out to determine whether conclusions presented in the heavily cited Health Canada assessment, Nawrot et al. [2], remain supported by more recent data. To that end, we reviewed data from 380 studies published between June 2001 and June 2015, which were identified from an initial batch of over 5,000 articles through a stringent search and evaluation process [1]. In the current paper, we use plain language to summarize our process and findings, with the intent of sharing additional context for broader reach to the general public. We addressed whether caffeine doses previously determined not to be associated with adverse effects by Health Canada (400 mg/day for healthy adults, 300 mg/day for pregnant women, 2. 5 mg/kg body weight/day for adolescents and children, and 10 g/day for acute effects) remain appropriate for five outcome areas (acute toxicity, cardiovascular toxicity, bone & calcium effects, behavior, and development and reproduction) in healthy adults, pregnant women, adolescents, and children. We used a weight-of-evidence approach to draw conclusions for each of the five outcomes, as well as more specific endpoints within those outcomes, which considered study quality, consistency, level of adversity, and magnitude of response. In general, updated evidence confirms the levels of intake put forth by Nawrot et al., as not being associated with any adverse health effects, and our results support a shift in caffeine research from healthy to sensitive populations.

The stimulant properties of caffeine are often promoted in pre-workout supplements (PWS) to assist with training, reduce the perception of fatigue, and for some brands, assist body fat loss. While manufacturers of PWS often indicate the inclusion of significant amounts of caffeine, no independent verification of the caffeine content of these products exists. The aim of this investigation was to independently assess the caffeine content of popular PWS in Australia and compare these values to nutrition information panel data. Fifteen PWS were tested for their caffeine content (both within and between batches of the same product). The caffeine content of selected PWS ranged from 91 to 387 mg·serve-1 . Only 6 of the 15 PWS nutrition information panels included details on caffeine content. The percent of caffeine present ranged from 59% to 176% of packaging claims. All but one PWS contained a variation of caffeine within and between batches that was considered "practically" significant (ie, ≥40 mg·serve-1 variation). Consumers are likely to be exposed to large and variable caffeine doses if ingesting PWS. Product information panels do little to improve consumer awareness of likely caffeine intakes.

Caffeine is a popular and widely consumed sporting ergogenic aid. Over the years, the effects of different caffeine doses have been researched, with the general consensus being that 3 to 6 mg/kg of caffeine represents the optimal dose for most people. Recently, there has been increased attention placed on lower (≤3 mg/kg) caffeine doses, with some research suggesting these doses are also ergogenic. However, a critical consideration for athletes is not merely whether caffeine is ergogenic at a given dose, but whether the consumed dose provides an optimized performance benefit. Following this logic, the aim of this review was to identify a potential oversight in the current research relating to the efficacy of lower caffeine doses. Although low caffeine doses do appear to bestow ergogenic effects, these effects have not been adequately compared with the currently accepted best practice dose of 3 to 6 mg/kg. This methodological oversight limits the practical conclusions we can extract from the research into the efficacy of lower doses of caffeine, as the relative ergogenic benefits between low and recommended doses remains unclear. Here, we examine existing research with a critical eye, and provide recommendations both for those looking to use caffeine to enhance their performance, and those conducting research into caffeine and sport. [Abstract copyright: Copyright © 2019 Elsevier Inc. All rights reserved.]

Insight into caffeine's equivocal effects on memory can be derived from work suggesting both emotional arousal and psychosocial stress increase false memory rates without increasing veridical memory. This study investigated how a range of caffeine doses affect veridical and false memory formation in nonhabitual consumers. A double-blind, repeated-measures design with caffeine (0 mg, 100 mg, 200 mg, 400 mg caffeine) was used to examine memory using the Deese-Roediger-McDermott (DRM) paradigm. Results showed that caffeine modulated arousal levels, peaking at 200 mg and returning to near baseline levels at 400 mg. Main effects of caffeine demonstrated higher critical lure recall and recognition ratings (i.e., false memory) as a function of dose, again peaking at 200 mg. Those who showed the highest arousal increases as a function of caffeine also tended to produce the highest false recall and recognition rates. Veridical memory was not affected. Results demonstrate that consumption of as little as 100 mg of ...

Made available in DSpace on 2013-09-27T14:53:45Z (GMT). No. of bitstreams: 1 WOS000291623600017.pdf: 397510 bytes, checksum: dd12033b1849c933defe8e898b98873f (MD5) Previous issue date: 2011-06-25 Made available in DSpace on 2013-09-30T18:08:02Z (GMT). No. of bitstreams: 1 WOS000291623600017.pdf: 397510 bytes, checksum: dd12033b1849c933defe8e898b98873f (MD5) Previous issue date: 2011-06-25 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:25:36Z No. of bitstreams: 1 WOS000291623600017.pdf: 397510 bytes, checksum: dd12033b1849c933defe8e898b98873f (MD5) Made available in DSpace on 2014-05-20T13:25:36Z (GMT). No. of bitstreams: 1 WOS000291623600017.pdf: 397510 bytes, checksum: dd12033b1849c933defe8e898b98873f (MD5) Previous issue date: 2011-06-25 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Caffeine is the psychostimulant drug most consumed in the world. This drug is present in food, beverages and medicines marketed for individuals of all ages. In spite of this, caffeine effects on adolescents are poorly understood. The aim of this study was to evaluate the differences on caffeine-induced locomotor stimulant or depressant effects in adolescent and adult rats. Adolescent (37-40 days old) or adult (70-74 days old) Wistar rats were tested for stimulant and depressant caffeine effects in two different experiments. The first was designed to evaluate the locomotor effect of caffeine in habituated rats. To this end, rats were previously habituated to test environment and had their locomotor activity registered following i.p. injections of vehicle or caffeine (3, 10, 30, 60 or 120 mg/kg). In the second experiment adolescent or adult rats were not habituated to the test environment and their locomotor activity was registered following i.p. injections of vehicle or caffeine (30, 60 or 120 mg/kg). In both experiments caffeine-induced a biphasic effect, with stimulation in small to moderate drug doses and no effect or locomotor depression in higher caffeine doses. Moreover, caffeine-induced locomotor stimulation was higher in adolescent than adult rats. Also, locomotor depression was only revealed in adult rats non-habituated to the test environment. These results suggest that adult and adolescent respond differently to caffeine indicating the need of more studies on the effects of caffeine in animals' models of adolescence. (C) 2011 Elsevier B.V. All rights reserved. Univ Estadual Paulista, Sch Pharmaceut Sci, Pharmacol Lab, UNESP, BR-14801902 Araraquara, SP, Brazil Universidade Federal de Uberlândia (UFU), Inst Biomed Sci, BR-38400902 Uberlandia, MG, Brazil Universidade Federal de São Carlos (UFSCar), Interinst Grad Program Physiol Sci, BR-13560 São Carlos, SP, Brazil Univ Estadual Paulista, Sch Pharmaceut Sci, Pharmacol Lab, UNESP, BR-14801902 Araraquara, SP, Brazil

The purpose of the present study was to examine the acute effects of a caffeine-containing supplement (SUPP) on one-repetition maximum (1-RM) bench press strength and time to running exhaustion (TRE) at a velocity that corresponded to 85% of the peak oxygen uptake ([latin capital V with dot above]O2peak). The study used a double-blinded, placebo-controlled, crossover design. Thirty-one men (mean +/- SD age = 23.0 +/- 2.6 years) were randomly assigned to take either the SUPP or placebo (PLAC) first. The SUPP contained 201 mg of caffeine, and the PLAC was microcrystalline cellulose. All subjects were tested for 1-RM bench press strength and TRE at 45 minutes after taking either the SUPP or PLAC. After 1 week of rest, the subjects returned to the laboratory and ingested the opposite substance (SUPP or PLAC) from what was taken during the previous visit. The 1-RM bench press and TRE tests were then performed in the same manner as before. The results indicated that the SUPP had no effect on 1-RM bench press strength or TRE at 85% [latin capital V with dot above]O2peak. It is possible that the acute effects of caffeine are affected by differences in training status and/or the relative intensity of the exercise task. Future studies should examine these issues, in addition to testing the acute effects of various caffeine doses on performance during maximal strength, power, and aerobic activities. These findings do not, however, support the use of caffeine as an ergogenic aid in untrained to moderately trained individuals.

In this work, the effects of different caffeine doses on cardiac activity have been evaluated by frequency domain analysis of laser Doppler flowmetry signal. Using different data acquisition units, the blood perfusion on human forearm middle finger tip has been recorded. Blood perfusion has been recorded before and immediately after the consumption of all caffeine doses. Different caffeine doses contain different amount of caffeine but approximately same amount of sugar. Recorded and pre-processed data have been analyzed using frequency spectrum within the frequency range of cardiac activity. It is found that the consumption of caffeine free dose increases the cardiac activity. Besides, the consumption of caffeinated doses decreases the cardiac activity with respect to normal condition (before consumption). As the amount of caffeine consumed increases, the cardiac activity improves. Result shows 42.9%, 32.2% and 39.4% decrement in cardiac activity due to the consumption of 27 mg, 48 mg, and 64 mg caffeine respectively. The consumption of 80 mg caffeine dose significantly increases the cardiac activity. The outcome indicates the reduction of heart functions due to the consumption of lower caffeine dose.

This review documents two opposing effects of caffeine and caffeine-containing energy drinks, i.e., their positive effects on athletic performance and their negative impacts on glucose tolerance in the sedentary state. Analysis of studies examining caffeine administration prior to performance-based exercise showed caffeine improved completion time by 3.6%. Similar analyses following consumption of caffeine-containing energy drinks yielded positive, but more varied, benefits, which were likely due to the diverse nature of the studies performed, the highly variable composition of the beverages consumed, and the range of caffeine doses administered. Conversely, analyses of studies administering caffeine prior to either an oral glucose tolerance test or insulin clamp showed a decline in whole-body glucose disposal of ~30%. The consequences of this resistance are unknown, but there may be implications for the development of a number of chronic diseases. Both caffeine-induced performance enhancement and insulin resistance converge with the primary actions of caffeine on skeletal muscle.

It has been suggested that mixing alcohol with energy drinks or other caffeinated beverages may alter the awareness of (or 'mask') intoxication. The proposed reduction in subjective intoxication may have serious consequences by increasing the likelihood of engaging in potentially dangerous activities while intoxicated. A literature search was conducted to collect all studies measuring subjective intoxication after administration of alcohol with energy drinks, or with other caffeinated alcoholic drinks compared with alcohol alone. The studies were critically reviewed and, where possible, included in a meta-analysis in order to determine whether masking exists after mixing alcohol with caffeinated beverages. Sixteen articles were identified, of which nine could be used for the meta-analysis. When including the higher caffeine dose studies, the meta-analysis revealed no significant masking effect (p=0.404). Similarly, when including the lower caffeine dose studies, no significant masking effect was found (p=0.406). Despite the large range of caffeine doses (2.0-5.5 mg/kg resulting in absolute levels of 46-383 mg) and alcohol levels 0.29-1.068 g/kg (resulting in blood alcohol concentration (BAC) from 0.032 to 0.12%) investigated, caffeine had no effect on the judgement of subjective intoxication.

Following an application from SmithKline Beecham Limited, submitted for authorisation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924/2006 via the Competent Authority of United Kingdom, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver an opinion on the scientific substantiation of a health claim related to caffeine and increased alertness. The food constituent, caffeine, which is the subject of the health claim, is sufficiently characterised. Increased alertness might be a beneficial physiological effect. A claim on caffeine and increased alertness, in the general adult population, for products containing at least 75 mg of caffeine per serving, has already been assessed by the Panel with a favourable outcome. In the present application, the applicant proposed that, in order to bear the claim, a product should contain at least 40 mg of caffeine per serving. In weighing the evidence, the Panel took into account that most studies which measured reaction time in various cognitive tasks found no effect of caffeine at doses < 75 mg. In the particular dose range between 40 and < 75 mg, no effect of caffeine was found on the majority of outcome measures of reaction time. The Panel notes that the majority of studies with caffeine doses of 75 mg or higher showed a significant reduction in measures of reaction time. On the basis of the evidence provided, the Panel reiterates its previous conclusion that, in order to bear the claim, a product should contain at least 75 mg caffeine per serving. The Panel concludes that a cause and effect relationship has not been established between the consumption of caffeine and increased alertness under the conditions of use proposed by the applicant.

Information processing is generally biased toward global cues, often at the expense of local information. Equivocal extant data suggests that arousal states may accentuate either a local or global processing bias, at least partially dependent on the nature of the manipulation, task, and stimuli. To further differentiate the conditions responsible for such equivocal results we varied caffeine doses to alter physiological arousal states and measured their effect on tasks requiring the retrieval of local versus global spatial knowledge. In a double-blind, repeated-measures design, non-habitual (Experiment 1; N = 36, M = 42.5 ± 28.7 mg/day caffeine) and habitual (Experiment 2; N = 34, M = 579.5 ± 311.5 mg/day caffeine) caffeine consumers completed four test sessions corresponding to each of four caffeine doses (0, 100, 200, 400 mg). During each test session, participants consumed a capsule containing one of the three doses of caffeine or placebo, waited 60 min, and then completed two spatial tasks, one involving memorizing maps and one spatial descriptions. A spatial statement verification task tested local versus global spatial knowledge by differentially probing memory for proximal versus distal landmark relationships. On the map learning task, results indicated that caffeine enhanced memory for distal (i.e., global) compared to proximal (i.e., local) comparisons at 100 (marginal), 200, and 400 mg caffeine in non-habitual consumers, and marginally beginning at 200 mg caffeine in habitual consumers. On the spatial descriptions task, caffeine enhanced memory for distal compared to proximal comparisons beginning at 100 mg in non-habitual but not habitual consumers. We thus provide evidence that caffeine-induced physiological arousal amplifies global spatial processing biases, and these effects are at least partially driven by habitual caffeine consumption.

PALLARES, J. G., V. E. FERNANDEZ-ELIAS, J. F. ORTEGA, G. MUNOZ, J. MUNOZ-GUERRA, and R. MORA-RODRIGUEZ. Neuromuscular Responses to Incremental Caffeine Doses: Performance and Side Effects. Med. Sci. Sports Exerc., Vol. 45, No. 11, pp. 2184-2192, 2013. Purpose: The purpose of this study was to determine the oral dose of caffeine needed to increase muscle force and power output during all-out single multijoint movements. Methods: Thirteen resistance-trained men underwent a battery of muscle strength and power tests in a randomized, double-blind, crossover design, under four different conditions: (a) placebo ingestion (PLAC) or with caffeine ingestion at doses of (b) 3 mgIkg j1 body weight (CAFF3mg), (c) 6 mgIkg j1 (CAFF6mg), and (d) 9 mgIkg j1 (CAFF9mg). The muscle strength and power tests consisted in the measurement of bar displacement velocity and muscle power output during free- weight full-squat (SQ) and bench press (BP) exercises against four incremental loads (25%, 50%, 75%, and 90% one-repetition maxi- mum (1RM)). Cycling peak power output was measured using a 4-s inertial load test. Caffeine side effects were evaluated at the end of each trial and 24 h later. Results: Mean propulsive velocity at light loads (25%-50% 1RM) increased significantly above PLAC for all caffeine doses (5.4%-8.5%, P = 0.039-0.003). At the medium load (75% 1RM), CAFF3mg did not improve SQ or BP muscle power or BP velocity. CAFF9mg was needed to enhance BP velocity and SQ power at the heaviest load (90% 1RM) and cycling peak power output (6.8%-11.7%, P = 0.03-0.05). The CAFF9mg trial drastically increased the frequency of the adverse side effects (15%-62%). Conclusions: The ergogenic dose of caffeine required to enhance neuromuscular performance during a single all-out contraction depends on the magnitude of load used. A dose of 3 mgIkg j1 is enough to improve high-velocity muscle actions against low loads, whereas a higher

Objective To analyse the distribution of caffeine doses obtainable from espresso coffee sold by a sample of commercial coffee vendors located on the Gold Coast, Qld, Australia. Design A cross section of “Espresso/short black” coffee samples were purchased and analysed for their caffeine content using micellar electrokinetic capillary chromatography (MEKC). Coffees were collected using systematic cluster sampling across five major retail centres. Results Ninety-seven espresso samples were analysed. The mean (±SD) quantity of caffeine was 106 ± 38 mg/serve with a concentration of 2473 ± 1092 mg/l. There was considerable variation in caffeine content. The range per serve was 25–214 mg whilst the concentration range was 580–7000 mg/l. Twenty-four samples (24.7%) contained 120 mg of caffeine or higher and 12 samples (12.3%) exceeded 167 mg per serve. Conclusions and implications The number of heavily caffeinated samples differentiates these findings from frequently cited caffeine values and supports similar data recently collected throughout the United Kingdom. As a result, the accuracy of any previous intake modelling regarding caffeine use in the Australian population is in doubt. The present data suggests that the probability of consumer exposure to high caffeine doses is greater than previously anticipated. Greater sample numbers from a broader selection of venues is required to confirm the extent of caffeine content variance within retail ground coffees.

Introduction It has been suggested that mixing alcohol with energy drinks (AMED) and other caffeinated beverages may alter the awareness of intoxication. The proposed reduction in subjective intoxication, also called “the masking effect”, may have serious consequences by increasing the likelihood of engaging in potentially dangerous activities such as driving while intoxicated. Aim The aim of this meta-analysis was to determine if mixing alcohol with caffeinated beverages alters subjective intoxication. Methods A literature search was conducted (August 21st, 2012) to collect all studies measuring subjective intoxication after administration of AMED, or other caffeinated alcoholic drinks compared to alcohol only. To this extent, PubMed and Embase were searched using the key words “alcohol”, “caffeine”, “energy drinks” and “intoxication”. The studies were critically reviewed and, where possible, included in a meta-analysis in order to determine whether masking exists after mixing alcohol with caffeinated beverages. Results Twelve studies were identified of which 8 could be used for the meta-analysis. When including higher caffeine doses (4 mg/kg) the meta-analysis revealed no significant masking effect (p= 0.477). Similarly, when including lower caffeine doses (2 mg/kg) no significant masking effect was found (p=0 .434). Despite the large range of caffeine content (46 - 383 mg) and alcohol levels (0.03% - 0.12% BAC) investigated, caffeine had no effect on the correct judgment of subjective intoxication. Conclusion Mixing alcohol with energy drink or other caffeinated beverages does not alter subjective intoxication.

The study investigated the independent and interactive effects of caffeine and expectancy on caffeine-related symptoms. High- and low-caffeine consumers were randomly assigned to either an expectancy or nonexpectancy instructional set and one of four caffeine doses. Subjects were administered the State-Trait Anxiety Inventory, (SpielbergerGorsuch, 1970) and a Symptom Questionnaire (Christensen, White, Krietsch,Steele, 1990) prior to and 45 min following consumption of one of the four caffeine doses. An analysis of covariance identified a significant main effect for the State-Trait Anxiety Inventory scores and significant main and interaction effects for four Symptom Questionnaire items. However, when the alpha levels were corrected for the increased probability of Type I error, using the Bonferroni procedure, these effects failed to achieve significance. These results suggest that previous reports of subjective caffeine effects are also suspect because of their failure to control for the increased probability of Type I error.

Background and Aims:Some previous studies have demonstrated an early effect of caffeine administration on subjective state, but none of them has explored its existence after the administration of decaffeinate coffee, nor the possible differences according to the gender. The aim of the present work was to investigate, using a realistic design (non-research settings and naturalistic administration of the drug), the early effects (10-30 min post-consumption) of a single low-moderate dose of caffeine (100 mg) and decaffeinate coffee on sleepiness and subjective activation.Methods:A random double-blind informed placebo controlled procedure was applied to a group of 688 healthy undergraduate volunteers (238 men) mean age 22.03 ± 2.21 years. Measures were recorded in two experimental sessions: morning 11:00-13:00h or afternoon 16:00-18:00h, in three moments before (30, 20 and 10 min.) averaged as a stable baseline, and three after (10, 20 and 30 min.) consumption.Results:Caffeine administration induces fewer somnolence (F= 159.776, p

It has previously been assumed that levels of caffeine typically found in decaffeinated beverages have no behavioural effects. However, recent findings from our laboratory indicate that caffeine doses as low as 9 mg have psychoactive properties which can endure for several hours. The current study aimed to establish the lowest active dose of caffeine and to ascertain the duration of any effects. Twenty participants took part in this randomised, placebo-controlled, double-blind, balanced-crossover study assessing the effects of three different doses of caffeine (2.5, 5, and 10 mg) administered in fruit juice. Cognitive performance, mood, autonomic activity and salivary caffeine were assessed pre-dose and at 1, 3, 6 and 9 h post-dose. Compared with placebo, performance was impaired by 2.5 mg, whilst 5 mg had negative effects on mood and mixed effects on performance and 10 mg improved performance. A number of these effects were apparent at 9 h post-treatment. Given that the average cup of decaffeinated coffee contains 3–5 mg caffeine, these results demonstrate that decaffeinated coffee is not inert as previously believed and this has implications for research which utilises decaffeinated coffee as placebo. Effects of caffeine are also longer-lasting than previously thought with effects apparent 9 h post-dose. This finding may offer an alternative explanation to withdrawal models for differing results in the literature pertaining to baseline performance in consumers and non-consumers of caffeine.

Novel tastes preceded a range of caffeine doses (10-80 mg/kg) in a taste aversion training trial. One week later rats which had doses of 30 mg or higher showed strong aversions as measured by a single bottle consumption test. The 10 and 20 mg dose produced the most hyperactivity and apparently enhanced intake of the taste paired with caffeine. During the training trial, rats receiving the 80 mg dose exhibited copious gapes and chin-rubs, mimetic responses to noxious tastes. Gapes also occurred in these subjects during the aversion test. Consumption was more sensitive than mimetic responding as a measure of the aversive effects of caffeine. Only the 80 mg dose produced neophobia. Tests with isotonic injections indicated that tonicity was not the source of the aversions.

Caffeine pretreatment was studied for its effects on d-amphetamine-induced locomotor activity. Caffeine (30 mg/kg) was given either simultaneously with or at one of several intervals (0.5, 1.5, 4.5, 12, and 13.5 hours) before d-amphetamine (1.5 mg/kg). Enhancement of d-amphetamine activity occurred with simultaneous and 30 min caffeine pretreatment. However, when given 12 or 13.5 hours before d-amphetamine, caffeine diminished the activity, measured in stabilimeter cages. Several doses of caffeine (7.5, 15, 30, and 60 mg/kg) were given in multiple treatments ending 12 hours before d-amphetamine (1.5 mg/kg) to determine the effective doses for attenuation of d-amphetamine-induced activity. Only 30 and 60 mg caffeine doses reduced d-amphetamine activity while also interfering with body weight gain.

Non-germinating barley seeds were treated with N -methyl- N -nitrosourea (MNU), methyl methanesulphonate (MMS) or ethyl methanesulphonate (EMS) and then exposed either to non-toxic caffeine doses ( i.e. doses having no biological effect and inducing no DNA single-strand breaks when applied alone) or to toxic doses ( i.e. doses reducing seed germination and seedling height but inducing no DNA single-strand breaks). Non-toxic doses of caffeine, applied to MNU, MMS and EMS treated seeds enhanced the mutagen-induced reduction of germination and seedling height but did not disturb the recovery from this damage, achieved by storage of the seeds at 30% water content. At the DNA level, these doses of caffeine did not increase the amount of mutagen-induced single-strand breaks in the treated (preformed) DNA and did not inhibit repair of mutagen-induced single-strand breaks during seed storage. However, non-toxic doses of caffeine affected the size of DNA strands, newly synthesized during 3 days of seed germination. Whereas the size of DNA strands after MMS and EMS treatment approached the size of the newly synthesized DNA in the controls, the DNA strands from treatment with MMS or EMS plus non-toxic caffeine doses were considerably smaller. Thus, it seems likely that caffeine, although applied before the DNA-synthesis, enhanced the biological damage by acting in the S-phase and inhibiting the repair of DNA damage in the newly synthesized DNA strands. Interaction of toxic caffeine doses with MNU led both to the potentiation of the mutagen-induced reduction of germination and seedling height, and to the inhibition of recovery from this damage during seed storage. On the DNA level. even toxic doses of caffeine did not increase the amount of MNU-induced single-strand breaks in the preformed DNA but inhibited completely the repair of these breaks during the seed storage.

Acute toxic dosage-dependent behavioral effects of caffeine were compared in adult males from seven inbred mouse strains (A/J, BALB/cJ, CBA/J, C3H/HeJ, C57BL/6J, DBA/2J, SWR/J). C57BL/6J, chosen as a "prototypic" mouse strain, was used to determine behavioral responses to a broad range (5-500 mg/kg) of caffeine doses. Five phenotypic characteristics--locomotor activity, righting ability, clonic seizure induction, stress-induced lethality, death without external stress--were scored at various caffeine doses in drug-naive animals under empirically optimized, rigidly constant experimental conditions. Mice (n = 12 for each point) received single IP injections of a fixed volume/g body weight of physiological saline carrier with or without caffeine in doses ranging from 125-500 mg/kg. Loss of righting ability was scored at 1, 3, 5 min post dosing and at 5 min intervals thereafter for 20 min. In the same animals the occurrence of clonic seizures was scored as to time of onset and severity for 20 min after drug administration. When these proceeded to tonic seizures, death occurred in less than 20 min. Animals surviving for 20 min were immediately stressed by a swim test in 25 degrees C water, and death-producing tonic seizures were scored for 2 min. In other animals locomotor activity was measured 15 or 60 min after caffeine administration. By any single behavioral criterion or a combination of these criteria, marked differences in response to toxic caffeine doses were observed between strains. These results indicate that behavioral toxicity testing of alkylxanthines in a single mouse strain may be misleading and suggest that toxic responses of the central nervous system to this class of compounds are genetically influenced in mammals.

Larvae of Drosophila melanogaster were fed with caffeine, and the induced lethality was recorded using two different methods. Wild a wild-type strain a whole dose-response curve was obtained. The two sexes were equally sensitive. Four genetically different strains, showing different MMS sensitivities, were tested with two caffeine doses. The strains differed significantly in their caffeine sensitivity, but there existed no correlation between MMS and caffeine sensitivity.

Male C3H inbred mice and male (101xC3H) F1 hybrids were treated with various caffeine doses over a long period. After the end of treatment the animals were dissected and the metaphase I figures of the cycle of spermatogenesis were analysed. The experiments revealed no distinct evidence for the induction of chromosomal aberrations in the cycle of spermatogenesis caused by caffeine up to metaphase I.

Summary We studied the role of caffeine in action monitoring as expressed by the error-related negativity (ERN), an event-related brain component that reflects anterior cingulate cortex (ACC) activity. In a double-blind, placebo-controlled, within-subjects experiment, two caffeine doses (3 and 5 mg/kg BW) and a placebo were dissolved in a cup of decaffeinated coffee and administered to 15 habitual coffee drinkers. Compared with placebo, both caffeine doses enlarged the ERN. The P2 and P3 amplitudes were not affected by caffeine. Thus, the enlarged ERN after caffeine reflects a specific effect on action monitoring. We conclude that consumption of a few cups of coffee intensifies central information processing, specifically the monitoring of ongoing cognitive processes for signs of erroneous outcomes. We also studied the effects of caffeine on task switching in alternated task (AABB) blocks and single-task (AAAA) blocks. Participants alternated between two tasks (A and B) in a predictable manner. Reaction time switch costs were reduced compared to placebo. ERPs revealed a negative deflection that developed within the preparatory interval, which was more negative for switch compared to repeat trials. This switch-related difference was increased under caffeine compared to placebo. These results suggest that a few cups of coffee improve task-switching performance by enhancing anticipatory processing such as task-set updating.