Effect of caffeine ingestion on time trial performance in cyclists: a systematic review and meta-analysis.

BACKGROUND: Caffeine, widely recognized as an ergogenic aid, has undergone extensive research, demonstrating its effectiveness to enhance endurance performance. However, there remains a significant gap in systematically evaluating its effects on time trial (TT) performance in cyclists. PURPOSE: This meta-analysis aimed to determine the efficacy of caffeine ingestion to increase cycling TT performance in cyclists and to evaluate the optimal dosage range for maximum effect. METHODS: A search of four databases was completed on 1 December 2023. The selected studies comprised crossover, placebo-controlled investigations into the effects of caffeine ingestion on cycling TT performance. Completion time (Time) and mean power output (MPO) were used as performance measures for TT. Meta-analyses were performed using a random-effects model to assess the standardized mean differences (SMD) in individual studies. RESULTS: Fifteen studies met the inclusion criteria for the meta-analyses. Subgroup analysis showed that moderate doses of caffeine intake (4-6 mg/kg) significantly improved cycling performance (SMD Time = -0.55, 95% confidence interval (CI) = -0.84 ~ -0.26, p < 0.01, I2 = 35%; SMD MPO = 0.44, 95% CI = 0.09 ~ 0.79, p < 0.05, I2 = 39%), while the effects of low doses (1-3 mg/kg) of caffeine were not significant (SMD Time = -0.34, 95% CI = -0.84 ~ 0.17, p = 0.19, I2 = 0%; SMD MPO = 0.31, 95% CI = -0.02 ~ 0.65, p = 0.07, I2 = 0%). CONCLUSION: A moderate dosage (4-6 mg/kg) of caffeine, identified as the optimal dose range, can significantly improve the time trial performance of cyclists, while a low dose (1-3 mg/kg) does not yield improvement. In addition, the improvements in completion time and mean power output resulting from a moderate dose of caffeine are essentially the same in cycling time trails.

The association of caffeine intake and prevalence of obesity among children and adolescents: A cross-sectional survey from NHANES 2011-2020 March.

BACKGROUND: Many studies have demonstrated the beneficial health effects of caffeine. However, its association with obesity prevalence and caffeine intake remains controversial. Notably, the impact of caffeine on children and adolescents needs to be more adequately represented in large-scale epidemiological investigations. OBJECTIVE: This study examines the association between caffeine intake and obesity prevalence in children and adolescents aged 2 to 19. METHODS: This study used the database from the National Health and Nutrition Examination Survey (NHANES, 2011-2020 March) to perform a cross-sectional study. A total of 10,001 classified children and adolescents were included in this analysis. All data were survey-weighted, and corresponding logistic regression models were performed to examine the associations between caffeine intake and the prevalence of obesity. RESULTS: In a fully adjusted model, a per-quartile increase in caffeine intake was associated with a 0.05% increased prevalence of obesity. In the subgroup analysis, the multivariate-adjusted ORs (95% CIs) of the prevalence of obesity for per-quartile 1.3497 (1.2014, 1.5163) increments in caffeine intake were 1.5961 (1.3127, 1.9406) for boys and 1.4418 (1.1861, 1.7525) for girls, 1.5807 (1.3131, 1.9027) for white race and 1.3181 (1.0613, 1.6370), 1.0500 (0.6676, 1.6515) for the age of 2-5, 1.4996 (1.1997, 1.8745) for the age of 6-12, and 1.2321 (0.9924, 1597) for the age of 13-19. CONCLUSION: The study suggested that higher caffeine intake may have a protective effect against obesity in specific subgroups, particularly among no overweight individuals. However, the association was not significant in other groups, indicating the need for a nuanced understanding of caffeine's impact on obesity in diverse populations.

Repeated caffeine intake suppresses cerebral grey matter responses to chronic sleep restriction in an A1 adenosine receptor-dependent manner: a double-blind randomized controlled study with PET-MRI.

Evidence has shown that both sleep loss and daily caffeine intake can induce changes in grey matter (GM). Caffeine is frequently used to combat sleepiness and impaired performance caused by insufficient sleep. It is unclear (1) whether daily use of caffeine could prevent or exacerbate the GM alterations induced by 5-day sleep restriction (i.e. chronic sleep restriction, CSR), and (2) whether the potential impact on GM plasticity depends on individual differences in the availability of adenosine receptors, which are involved in mediating effects of caffeine on sleep and waking function. Thirty-six healthy adults participated in this double-blind, randomized, controlled study (age = 28.9 ± 5.2 y/; F:M = 15:21; habitual level of caffeine intake < 450 mg; 29 homozygous C/C allele carriers of rs5751876 of ADORA2A, an A2A adenosine receptor gene variant). Each participant underwent a 9-day laboratory visit consisting of one adaptation day, 2 baseline days (BL), 5-day sleep restriction (5 h time-in-bed), and a recovery day (REC) after an 8-h sleep opportunity. Nineteen participants received 300 mg caffeine in coffee through the 5 days of CSR (CAFF group), while 17 matched participants received decaffeinated coffee (DECAF group). We examined GM changes on the 2nd BL Day, 5th CSR Day, and REC Day using magnetic resonance imaging and voxel-based morphometry. Moreover, we used positron emission tomography with [18F]-CPFPX to quantify the baseline availability of A1 adenosine receptors (A1R) and its relation to the GM plasticity. The results from the voxel-wise multimodal whole-brain analysis on the Jacobian-modulated T1-weighted images controlled for variances of cerebral blood flow indicated a significant interaction effect between caffeine and CSR in four brain regions: (a) right temporal-occipital region, (b) right dorsomedial prefrontal cortex (DmPFC), (c) left dorsolateral prefrontal cortex (DLPFC), and (d) right thalamus. The post-hoc analyses on the signal intensity of these GM clusters indicated that, compared to BL, GM on the CSR day was increased in the DECAF group in all clusters  but decreased in the thalamus, DmPFC, and DLPFC in the CAFF group. Furthermore, lower baseline subcortical A1R availability predicted a larger GM reduction in the CAFF group after CSR of all brain regions except for the thalamus. In conclusion, our data suggest an adaptive GM upregulation after 5-day CSR, while concomitant use of caffeine instead leads to a GM reduction. The lack of consistent association with individual A1R availability may suggest that CSR and caffeine affect thalamic GM plasticity predominantly by a different mechanism. Future studies on the role of adenosine A2A receptors in CSR-induced GM plasticity are warranted.

Quality and fertilizing ability of frozen-thawed porcine sperm separated using a migration sedimentation method.

We evaluated the quality and fertilizing ability of frozen-thawed porcine sperm that were selected using a commercially available device (MIGLIS, Menicon Life Science) consisting of three parts: an outer lid, an inner lid, and a tube. Firstly, to determine an adequate concentration of caffeine for separation, frozen-thawed sperm were incubated with different concentrations of caffeine (0, 1, 2.5, 5, and 10 mM) in a MIGLIS device. To determine the appropriate incubation time for separating sperm in the MIGLIS device, frozen-thawed sperm were incubated with 2.5 mM caffeine for 5, 10, 15, or 20 min. To evaluate the fertilization and embryo development of oocytes fertilized with frozen-thawed sperm separated into two regions (outer and inner) in the MIGLIS device, the separated sperm from the three boars was used to fertilize in vitro-matured oocytes and cultured in vitro for 7 days. Sperm quality parameters of sperm collected from the inner tube after incubation with 2.5 mM caffeine were superior to sperm incubated without caffeine. Moreover, sperm collected from the inner tube after incubation for 10 min had a higher progressive motility. The rate of blastocyst produced from spermatozoa collected from the inner tube after incubation with 2.5 mM caffeine for 10 min significantly increased compared to that produced from spermatozoa from the outer tube, regardless of the boar. In conclusion, sperm sorting using the MIGLIS device may be useful for separating high-quality sperm after incubation with 2.5 mM caffeine for 10 min to improve blastocyst formation.

Quality of Arabica coffee grown in Brazilian Savannah and impact of potassium sources.

Located in Brazil's Central Plateau, the Cerrado Savannah is an emerging coffee-growing region with significant potential for the national coffee market. This study investigated the impact of potassium fertilization on Arabica coffee quality in the Cerrado, using three potassium sources (K2SO4, KCl, and KNO3) and five cultivars (Arara, Aranãs, IPR103, Catiguá and Topázio) across two consecutive harvests. We focused on productivity, granulometry, chemical composition, and sensory characteristics. No significant difference in productivity across the cultivars studied or potassium sources as isolated factors were observed. Regarding chemical parameters, potassium sources only affected NO3- and SO42- levels in the grains. Cultivar-specific differences were noted in caffeine (CAF), citric acid (CA), and sucrose (SUC), highlighting a strong genetic influence. K2SO4 improved productivity in Arara (15 %) and IPR103 (11 %), while KNO3 reduced flat grain percentage to 70 % in Catiguá. Sensory evaluation showed that all potassium sources and cultivars produced specialty coffees, with the Arara cultivar treated with K2SO4 achieving the highest SCA score (83.3) while IPR 103 treated with KCl scored the lowest at 78. Only three treatments were below but very close to the threshold (80). Multivariate analysis indicated a trend where specific treatments correlated with higher productivity and quality. Despite the subtle differences in productivity and quality among potassium sources, a cost-benefit analysis may favor KCl due to its affordability, suggesting its viability as a potassium fertilization option in coffee cultivation. Future research is needed to confirm these trends and optimize potassium source selection to enhance coffee quality in the Cerrado.

Active ischemic pre-conditioning does not additively improve short-term high-intensity cycling performance when combined with caffeine ingestion in trained young men.

We investigated the effect of ischemic preconditioning (IPC) with and without caffeine supplementation on mean power output (MPO) during a 4-min cycling time-trial (TT). In a double-blinded, randomized, crossover-design, 11 trained men performed a TT on 4 days separated by ∼1 week. One hour before TT, participants ingested either caffeine (3 mg kg bw-1) or placebo pills, after which femoral blood-flow was either restricted with occlusion cuffs inflated to ∼180 mmHg (IPC), or sham-restricted (0-10 mmHg; Sham) during 3 × 2-min low-intensity cycling (10% of incremental peak power output). Then, participants performed a standardized warm-up followed by the TT. Plasma lactate and K+ concentrations and ratings of perceived exertion (RPE) were measured throughout trials. TT MPO was 382 ± 17 W in Placebo + Sham and not different from Placebo + IPC (-1 W; 95% CI: -9 to 7; p = 0.848; d: 0.06), whereas MPO was higher with Caffeine + Sham (+6W; 95% CI: -2 to 14; p = 0.115; d: 0.49) and Caffeine + IPC (+8 W; 95% CI: 2-13; p = 0.019; d: 0.79) versus Placebo + Sham. MPO differences were attributed to caffeine (caffeine main-effect: +7 W; 95% CI: 2-13; p = 0.015; d: 0.54. IPC main-effect: 0 W; 95% CI: -6 to 7; p = 0.891; d: 0.03; caffeine × IPC interaction-effect: p = 0.580; d: 0.17). TT RPE and plasma variables were not different between treatments. In conlcusion, IPC with co-ingestion of placebo does not improve short-term high-intensity performance in trained men versus a double-placebo control (Placebo + Sham) and does not additively enhance performance with caffeine. These data do not support IPC as a useful strategy for athletes prior to competition but confirms caffeine's performance-enhancing effect.

The influence of temperature on the impacts of caffeine in mussels: Evaluating subcellular impacts and model predictions.

In aquatic ecosystems, the presence of pharmaceuticals, particularly caffeine (CAF), has been linked to wastewater discharge, hospital waste, and the disposal of expired pharmaceutical products containing CAF. Additionally, rising temperatures due to climate change are anticipated in aquatic environments. This study aimed to assess the toxicity of various CAF concentrations under current (17 °C) and projected (21 °C) temperature conditions, using the mussel Mytilus galloprovincialis as a bioindicator species. Subcellular impacts were evaluated following 28 days of exposure to four CAF concentrations (0.5; 1.0; 5.0; 10.0 µg/L) at the control temperature (17 °C). Only effects at an environmentally relevant CAF concentration (5.0 µg/L) were assessed at the highest temperature (21 °C). The overall biochemical response of mussels was evaluated using non-metric Multidimensional Scaling (MDS) and the Integrated Biomarker Response (IBR) index, while the Independent Action (IA) model was used to compare observed and predicted responses. Results showed that at 17 °C, increased CAF concentrations were associated with higher metabolism and biotransformation capacity, accompanied by cellular damage at the highest concentration. Conversely, under warming conditions (21 °C), the induction of antioxidant enzymes was observed, although insufficient to prevent cellular damage compared to the control temperature. Regarding neurotoxicity, at 17 °C, the activity of the acetylcholinesterase enzyme was inhibited up to 5.0 µg/L; however, at 10.0 µg/L, activity increased, possibly due to CAF competition for adenosine receptors. The IA model identified a synergistic response for most parameters when CAF and warming acted together, aligning with observed results, albeit with slightly lower magnitudes.

Predicting gastric emptying of drug substances taken under postprandial conditions by combination of biorelevant dissolution and mechanistic in silico modeling.

Physiologically based pharmacokinetic (PBPK) models can help to understand the effects of gastric emptying on pharmacokinetics and in particular also provide a platform for understanding mechanisms of food effects, as well as extrapolation between different postprandial conditions, whether standardized clinical or patient-oriented, non-clinical conditions. By integrating biorelevant dissolution data from the GastroDuo dissolution model into a previously described mechanistic model of fed-state gastric emptying, we simulated the effects of a high-calorie high-fat meal on the pharmacokinetics of sildenafil, febuxostat, acetylsalicylic acid, theobromine and caffeine. The model was able to simulate the variability in Cmax and tmax caused by the presence of the stomach road. The main influences investigated to affect the gastric emptying process were drug solubility (theobromine and caffeine), tablet dissolution rate (acetylsalicylic acid) and sensitivity to gastric motility (sildenafil and febuxostat). Finally, we showed how PBPK models can be used to extrapolate pharmacokinetics between different prandial states using theobromine as an example with results from a clinical study being presented.

Timing Matters: Time of Day Impacts the Ergogenic Effects of Caffeine-A Narrative Review.

Caffeine has attracted significant attention from researchers in the sports field due to its well-documented ergogenic effects across various athletic disciplines. As research on caffeine continues to progress, there has been a growing emphasis on evaluating caffeine dosage and administration methods. However, investigations into the optimal timing of caffeine intake remain limited. Therefore, this narrative review aimed to assess the ergogenic effects of caffeine administration at different times during the morning (06:00 to 10:00) and evening (16:00 to 21:00). The review findings suggest that circadian rhythms play a substantial role in influencing sports performance, potentially contributing to a decline in morning performance. Caffeine administration has demonstrated effectiveness in mitigating this phenomenon, resulting in ergogenic effects and performance enhancement, even comparable to nighttime levels. While the specific mechanisms by which caffeine regulates circadian rhythms and influences sports performance remain unclear, this review also explores the mechanisms underlying caffeine's ergogenic effects, including the adenosine receptor blockade, increased muscle calcium release, and modulation of catecholamines. Additionally, the narrative review underscores caffeine's indirect impact on circadian rhythms by enhancing responsiveness to light-induced phase shifts. Although the precise mechanisms through which caffeine improves morning performance declines via circadian rhythm regulation necessitate further investigations, it is noteworthy that the timing of caffeine administration significantly affects its ergogenic effects during exercise. This emphasizes the importance of considering caffeine intake timing in future research endeavors to optimize its ergogenic potential and elucidate its mechanisms.

Modafinil Subjectively Does Not Impair Sleep in Aviators After a Period of Extended Wakefulness.

INTRODUCTION: Modafinil is used as a countermeasure to limit the effects of fatigue in military aviation. However, literature is conflicting about its negative effects on subsequent sleep.METHODS: This randomized placebo-controlled trial conducted by the Center of Man in Aviation of the Royal Netherlands Airforce is part of a larger study. It included 32 subjects (mean age 35 yr old, 84% male) who followed a normal daily routine and stayed awake the subsequent night. At midnight, all subjects received either 300 mg caffeine, 200 mg modafinil, or placebo. At the end of the test night, subjects were awake for a median period of 26 h. Afterwards, sleep questionnaires containing qualitative (Groningen Sleep Quality Scale) and quantitative parameters of sleep for the subsequent day (recovery sleep) and consecutive night (post-test sleep) were completed and statistically analyzed using Friedman and Wilcoxon signed rank tests.RESULTS: A statistically significant difference in the reported recovery sleep was observed. The modafinil group slept 30% shorter than placebo, but sleep efficiency was not statistically different. Quantitatively post-test sleep did not vary statistically significantly between the three groups. However, Groningen Sleep Quality Scale scores were lower post-test than pre-test in the modafinil group, while this was not the case in the caffeine and placebo group.DISCUSSION:This study found that modafinil subjectively does not negatively impact recovery sleep or subsequent nighttime sleep after an extended period of wakefulness and suggests it may decrease the need for recovery sleep compared to placebo or caffeine.Wingelaar-Jagt YQ, Wingelaar TT, Riedel WJ, Ramaekers JG. Modafinil subjectively does not impair sleep in aviators after a period of extended wakefulness. Aerosp Med Hum Perform. 2024; 95(6):290-296.

Caffeine Improves Sprint Time in Simulated Freestyle Swimming Competition but Not the Vertical Jump in Female Swimmers.

Caffeine (CAF) has been shown to be an effective ergogenic aid in enhancing sports performance, including vertical jump (VJ), sprint, balance, agility, and freestyle swimming performance (FSP). However, whether acute CAF supplementation improves FSP in moderately trained female swimmers has not been well documented. Therefore, this study aimed to investigate the effects of CAF intake on vertical jump, balance, auditory reaction time (ART), and swimming performance in female swimmers. In a double-blind, cross-over design, eight moderately trained female swimmers (age: 21.3 ± 1.4 years, height: 161.2 ± 7.1 cm, body mass: 56.3 ± 6.7 kg, body mass index (BMI): 21.9 ± 1.3 kg/m2, and habitual CAF intake: 246.4 ± 111.4 mg/day) ingested caffeine (CAF) (6 mg/kg) or a placebo (PLA) 60 min before completing VJ, balance, ART, and 25/50 m FSP. CAF supplementation resulted in a significantly lower time both in 25m (p = 0.032) and 50m (p = 0.033) FSP. However, CAF resulted in no significant difference in VJ, ART, and RPE (p > 0.05). Balance test results showed a non-significant moderate main effect (d = 0.58). In conclusion, CAF seems to reduce time in short-distance swimming performances, which could be the determinant of success considering the total time of the race. Thus, we recommend coaches and practitioners incorporate CAF into swimmers' nutrition plans before competitions, which may meet the high performance demands.

Caffeinated Chewing Gum Improves Basketball Shooting Accuracy and Physical Performance Indicators of Trained Basketball Players: A Double-Blind Crossover Trial.

(1) Background: This study investigated the effects of caffeinated chewing gum on the basketball-specific performance of trained basketball players. A double-blind, randomized crossover design was employed. (2) Methods: Fifteen participants (age: 20.9 ± 1.0 years; height: 180.9 ± 5.4 cm; mass: 77.2 ± 7.5 kg; training age: 8.2 ± 0.3 years) were recruited and divided into a caffeine trial (CAF) and placebo trial (PL). The participants in the CAF trial chewed gum containing 3 mg/kg of caffeine for 10 min, while those in the PL trial chewed a placebo gum without caffeine. Following a 15 min rest, all the participants completed basketball-specific performance tests. (3) Results: The free throw accuracy for the CAF trial was significantly higher than that for the PL trial (CAF: 79.0 ± 4.31%; PL: 73.0 ± 9.16%; p = 0.012; Cohen's d = 0.94). Additionally, the CAF trial demonstrated significantly better performance in the 20 m segmented dash (CAF: 2.94 ± 1.12 s; PL: 3.13 ± 0.10 s; p < 0.001; Cohen's d =1.8) and squats (p < 0.05), and exhibited lower fatigue indexes (CAF: 3.6 ± 1.6%; PL: 5.2 ± 1.6%; p = 0.009; Cohen's d =1.0). (4) Conclusions: These findings suggest that chewing gum containing 3 mg/kg of caffeine offers moderate-to-large improvements in key performance aspects relevant to professionally trained basketball players.

Polyphenols vs. Caffeine in Coffee from Franchise Coffee Shops: Which Serving of Coffee Provides the Optimal Amount of This Compounds to the Body.

The scientific literature indicates that there is a limited number of data on the content of bioactive components in coffees consumed "on the go". Therefore, this study examined the polyphenol and caffeine content of different types of coffee from franchise coffee shops, and the caffeine/total polyphenol ratio. The five most popular types of coffee purchased in six franchise coffee shops in Warsaw were analysed. A total of 120 coffee samples were tested. A significant positive (r = 0.7407, p < 0.001) correlation was found between the total polyphenol and caffeine content in all coffee types tested. Per unit volume, espresso coffee had the highest significant (p < 0.005) average total polyphenol and caffeine contents (232.9 ± 63.9 mg/100 mL and 198.6 ± 68.3 mg/100 mL, respectively). After taking into account the coffee's serving size, a serving of Americano provided significantly (p < 0.05) the most total polyphenol (average 223.5 ± 81.5 mg), while the highest caffeine content was provided by a serving of ice latte/latte frappe (average 136 ± 57.0 mg). The most favourable ratio of caffeine to total polyphenols (0.56) was found in a serving of Americano coffee; therefore, it seems that this coffee can be considered optimal in terms of the content of both compounds. These findings demonstrate that the polyphenol and caffeine contents of coffees offered in franchise coffee shops are closely related to the serving size.

Placebo Effect of Caffeine on Physiological Parameters and Physical Performance.

This study aimed to analyse the placebo effect associated with a high dose of caffeine (9 mg/kg) on heart rate and its variability and on strength tests. METHODS: 18 participants experienced in strength training (19.7 ± 2.3 years; 72.2 ± 15.0 kg; 169.6 ± 9.0 cm) performed two days of trials (caffeine-informed/placebo-ingested (placebo) and non-ingested (control)). Firstly, heart rate and its variability were measured while participants lay down for 15 min. After that, bench press and squat tests were performed at 3 different loads (50%, 75% and 90% of 1RM). Perception of performance, effort and side effects were also evaluated. RESULTS: no differences were found in the vast majority of strength variables analysed. Resting heart rate decreased in the placebo trial (60.39 ± 10.18 bpm control vs. 57.56 ± 9.50 bpm placebo, p = 0.040), and mean RR increased (1020.1 ± 172.9 ms control vs. 1071.5 ± 185.7 ms placebo, p = 0.032). Heart rate variability and perception of performance and effort were similar between conditions (p > 0.05 in all cases). Side effects such as activeness and nervousness were reported while consuming the placebo. CONCLUSIONS: the placebo effect did not modify performance in the majority of the strength test variables, HRV and perception of performance and effort. However, resting heart rate was reduced, mean RR increased, and some side effects appeared in the placebo trial.

Comparing the number of outdoor sugar-sweetened beverage and caffeinated beverage advertisements near schools by school type and school-level economic advantage.

INTRODUCTION: Sugar-sweetened beverage and caffeinated beverage consumption are associated with a variety of health issues among youth. Food and beverage marketing has been shown to affect youth's preferences, purchases, and consumption of marketed products. Previous research suggests that outdoor food and beverage marketing differs by community demographics, with more advertisements in lower-income communities and near schools. The purpose of this study is to examine the density of sugar-sweetened and caffeinated beverage advertisements near schools by school type (middle vs. high school) and by school-level SES. METHODS: Data are from the Outdoor Measuring and Evaluating the Determinants and Influence of Advertising (MEDIA)study, which documented and described all outdoor food and beverage advertisements near 47 middle and high schools in 2012. Beverage advertisements were categorized as: sugar-sweetened/caffeinated, sugar-sweetened/non-caffeinated, non-sugar-sweetened/caffeinated, or non-sugar-sweetened/non-caffeinated. Schools were categorized by type (middle vs high) and by SES as determined by the percentage of students qualifying for free or reduced-price lunch. Bootstrapped non-parametric Mann-Whitney U tests compared the number of advertisements in each category by school type and school-level SES (higher vs lower). RESULTS: Compared to schools with higher SES, schools with lower SES had significantly more advertisements for sugar-sweetened/non-caffeinated beverages (Medianlow = 28.5 (IQR 17-69), vs Medianhigh = 10.5 (IQR 4-17) (p = 0.002)., sugar-sweetened non-caffeinated (Medianlow = 46 (IQR 16-99) vs Medianhigh = 13.5 (IQR 6-25), p = 0.002), -sugar-sweetened caffeinated (Medianlow = 12 (IQR 8-19) vs Medianhigh = 6 (IQR 2-8), p = 0.000), and non-sugar-sweetened non-caffeinated (Medianlow = 30 (IQR 13-65) vs Medianhigh = 14 (IQR 4-29), p = 0.045).There were no significant differences by school type. CONCLUSION: This study adds to the literature demonstrating pervasive marketing of unhealthy products in lower-income communities. Disproportionate exposure to sugar-sweetened and caffeinated beverage advertisements in lower-income communities may contribute to the disparities in associated health outcomes by economic status.

Caffeine Expectancy Does Not Influence the Physical Working Capacity at the Fatigue Threshold.

ABSTRACT: Ambrozy, CA, Hawes, NE, Hayden, OL, Sortzi, I, and Malek, MH. Caffeine expectancy does not influence the physical working capacity at the fatigue threshold. J Strength Cond Res 38(6): 1056-1062, 2024-The placebo effect occurs when a desired outcome is experienced due to the belief that a treatment is effective, even in the absence of an active ingredient. One explanation for this effect is based on a person's expectations of a drug or supplement. Although caffeine's effects on sports performance have been studied, little is known about how expectations of caffeine affect neuromuscular fatigue during continuous muscle action. The physical working capacity at the fatigue threshold (PWCFT) can be used to assess neuromuscular fatigue noninvasively using surface electromyography. Thus, the purpose of this study was to investigate whether caffeine expectancy influences PWCFT. We hypothesized that regardless of expectancy, caffeine consumption would delay neuromuscular fatigue. The study involved 8 healthy college-aged men (mean ± SEM: age, 25.6 ± 1.0 years) who visited the laboratory on 4 occasions, each separated by 7 days. The subjects completed 4 experimental conditions, in random order, where they were told that they were consuming caffeine or placebo and either received caffeine or placebo. After consuming the drink, the subjects remained in the laboratory for an hour and then performed an incremental exercise test. The results showed that the condition where subjects were told that they were consuming caffeine and received caffeine had significantly higher mean values for maximal power output (F(3, 21) = 11.75; p < 0.001), PWCFT (F(3, 21) = 12.28; p < 0.001), PWCFT (%maximal power output; F(3, 21) = 8.75; p < 0.001), and heart rate at end exercise (%predicted; F(3, 21) = 3.83; p = 0.025) compared with the 2 conditions where placebo was received. However, no statistically significant mean differences were found from the condition where subjects were told that they were consuming placebo but consuming caffeine. This suggests that a person's expectancy and potential somatic response may serve as a cue for how an ergogenic aid or placebo could affect subsequent performance.

Enteric-Coated Capsules Providing Reliable Site-Specific Drug Delivery to the Distal Ileum.

Nefecon, a targeted-release capsule formulation of budesonide approved for the reduction of proteinuria in adults with primary immunoglobulin A nephropathy, targets overproduction of galactose-deficient immunoglobulin A type 1 in the Peyer's patches at the gut mucosal level. To investigate whether the commercial formulation of Nefecon capsules reliably releases budesonide to the distal ileum, a human study was conducted with test capsules reproducing the delayed-release function of Nefecon capsules. Caffeine was included in the test capsules as a marker for capsule opening in the gut since it appears rapidly in saliva after release from orally administered dosage forms. Magnetic resonance imaging with black iron oxide was used to determine the capsule's position in the gut at the time caffeine was first measured in saliva and additionally to directly visualize dispersion of the capsule contents in the gut. In vitro dissolution results confirmed that the test capsules had the same delayed-release characteristics as Nefecon capsules. In 10 of 12 human volunteers, the capsule was demonstrated to open in the distal ileum; in the other two subjects, it opened just past the ileocecal junction. These results compared favorably with the high degree of variability seen in other published imaging studies of delayed-release formulations targeting the gut. The test capsules were shown to reliably deliver their contents to the distal ileum, the region with the highest concentration of Peyer's patches.

Development of a novel UPLC approach to co-prediction of four active compounds in a multi-component pharmaceutical preparation.

In this work, a new ultra-performance liquid chromatography method based on photodiode array detection (UPLC-PDA) was first developed for the quantitative analysis of the quaternary mixture of ascorbic acid (AA), paracetamol (PAR), caffeine (CAF) and chlorpheniramine maleate (CPA) in a commercial dosage form. The developed UPLC-PDA method offered a new possibility for the co-determination of four active ingredients in a drug combination with short run time and simple sample preparation. The successful chromatographic separation of the four drugs was performed using a Waters Acquity UPLC BEH C18 column (1.7 µm 2.1 × 100 mm) (Mildford, USA) and a mobile phase consisting of water (12 %), acetonitrile (13 %) and 0.1 M H3PO4 (75 %) at a flow rate of 0.25 mL/min. The validation of the proposed UPLC-PDA approach was verified by analyzing synthetic mixtures, inter- and intra-day experiments, and commercial powder samples and provided satisfactory results.

Effects of caffeine on temporal perception in Rattus norvegicus.

We report two studies that tested the effects of caffeine, the world's most widely used psychoactive drug, on temporal perception. We trained Wistar rats using the Bisection Procedure (Experiment 1) or the Stubbs' Procedure (Experiment 2) to discriminate between short and long light stimuli. Once training finished, we administered caffeine orally (0, 9.6, and 96.0 mg/kg for Experiment 1 and 0, 9.6, 19.2, and 38.4 mg/kg for Experiment 2) 15 minutes prior to testing. Relative to the control condition, the 9.6 mg/kg condition (Experiments 1 and 2) and the 19.2 mg/kg condition (Experiment 2) resulted in an increase in proportion of choosing the long response. Meanwhile, overall accuracy was not affected by any condition in both experiments. Taken together, these results are consistent with the notion that caffeine, at some doses, speeds up temporal perception. However, it is not clear why the effect disappears at higher doses.

Association between caffeine metabolites in urine and muscle strength in young and older adults: A cross-sectional study from NHANES 2011-2012.

BACKGROUND: Elevated levels of reactive oxygen species may contribute to the gradual decline in muscle strength over time. Although caffeine and its metabolites have antioxidant properties that can mitigate oxidative stress, the association of caffeine and its metabolites with muscle strength remains unknown. AIM: To investigate whether caffeine metabolites in urine are associated with muscle strength in young and older adults. METHODS: A cross-sectional study was conducted with 1145 individuals aged over 20 years (n = 801 < 60 years and n = 344 ≥ 60 years) from the National Health and Nutrition Examination Survey (NHANES) 2011-2012. Muscle strength was assessed using a handgrip dynamometer, and combined grip strength was determined by summing the highest value from each hand. Caffeine and its metabolites in urine were quantified using ultra-high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (1-methyluric acid, 3-methyluric acid, 7-methyluric acid, 1,3-dimethyluric acid, 1,7-dimethyluric acid, 3,7-dimethyluric acid, 1,3,7-trimethyluric acid, 1-methylxanthine, 3-methylxanthine, 7-methylxanthine, 1,3-dimethylxanthine, 1,7-dimethylxanthine, 3,7-dimethylxanthine, 1,3,7-trimethylxanthine, 5-acetylamino-6-amino-3-methyluracil). Linear regression analyses were performed to determine the association of caffeine and its metabolites with muscle strength in young and older adults, adjusting for confounders. RESULTS: Positive associations between muscle strength and levels of 7-methyluric acid (ß = 0.029; p = 0.021), 1,3-dimethyluric acid (ß = 0.008; p = 0.004), 3,7-dimethyluric acid (ß = 0.645; p = 0.012), 3-methylxanthine (ß = 0.020; p = 0.002), 7-methylxanthine (ß = 0.020; p = 0.006), 1,3-dimethylxanthine (theophylline) (ß = 0.030; p = 0.004) and 3,7-dimethylxanthine (theobromine) (ß = 0.035; p = 0.029) were observed in older adults. In contrast, no such associations were noted in young adults. CONCLUSION: Our study indicates a positive association between certain caffeine metabolites in urine and muscle strength in older adults, but not in younger individuals. These findings indicate that specific caffeine metabolites may contribute to an antioxidant role especially in older adults.