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Simple Summary: This study explored the effects of different caffeine doses on nutrient digestion and fermentation in a simulated rumen environment. The main goal was to improve our understanding of how caffeine might influence these important metabolic processes in the rumen when a lactating cow diet is used. Here, we report that a dose of caffeine (50 ppm) improved the digestibility of dry/organic matter and starch while reducing the protozoa numbers and ammonia concentration, which are related to ruminal protein metabolism. However, higher caffeine doses (above 50 ppm) began to negatively impact these parameters. Our observations suggest that caffeine, a naturally occurring compound in several plants such as coffee, cacao, and tea, could potentially be used to enhance digestion and fermentation in ruminants. This research is valuable to our understanding of anaerobic fermentation in the rumen as it demonstrates the use of this plant secondary metabolite to enhance nutrient utilization and milk production and other benefits to management and the environment. Caffeine is a plant secondary metabolite, commonly known for its bioactivity properties. This molecule increases microbial activity during anaerobic digestion. The aim of this study was to determine the effects of caffeine doses on the rumen fermentation profile and nutrient digestibility when continuous culture fermenters were fed a lactating cow's diet. We hypothesize that adding caffeine doses into continuous culture fermenters with a rumen fluid inoculum will not affect anaerobic fermentation or nutrient utilization. Fermenters were fed twice a day (at 0800 and 2000 h) with an experimental diet of high-producing dairy cows (53.55 g/DM day; Forage:Concentrate ratio, F:C of 40:60). Four levels of caffeine (0 ppm, 50 ppm, 100 ppm, and 150 ppm) were added to the diets as a treatment. The experiment was arranged in a randomized complete block design. Two blocks of four fermenters were run in two replicated periods of ten days. Statistical analyses were conducted in SAS version 9.4 for Windows (SAS Institute Inc., Cary, NC, USA) using the GLIMMIX procedure. The addition of caffeine at a 50 ppm dose on continuous culture fermentation decreased the protozoal counts (Diplodinium spp.) (p = 0.03) and ammonia concentrations (p < 0.05). A treatment of 50 ppm of caffeine increased the DM, OM, and starch digestibility (p < 0.05). When caffeine doses increased further than 50 ppm, the OM, DM, and starch digestibility decreased linearly (p = 0.01). The total volatile fatty acids and fatty acid proportions were unaffected. However, the acetate-to-propionate ratio (A:P) tended to decrease linearly among treatments (p = 0.07). The means of pH measurements and maximum pH had a significantly linear decrease effect (p < 0.01). Caffeine may represent a potential rumen fermentation modifier for use in lactating cow diets. [ABSTRACT FROM AUTHOR]

Caffeine is the world's most popular stimulant and is consumed daily by a significant portion of the world's population through coffee, tea, soda, and energy drinks. Consumers often shop online and in physical stores immediately after or while consuming caffeine. This is further facilitated by the increasing prevalence of coffee shops and by the phenomenon of some retail stores having in-store coffee bars and offering complimentary caffeinated beverages. This research examines how caffeine consumption before shopping influences purchase behavior. The results of a series of experiments conducted in the field (at multiple retail stores across different countries) and in the lab show that consuming a caffeinated (vs. noncaffeinated) beverage before shopping enhances impulsivity in terms of more items purchased and higher spending. This effect is stronger for "high-hedonic" products and attenuated for "low-hedonic" products. These findings are important for managers to understand how a seemingly unrelated behavior (i.e., caffeine consumption) in and/or around the store affects spending. From a consumer perspective, although moderate amounts of caffeine consumption can have positive health benefits, there can be unintended negative financial consequences of caffeine intake on spending. Thus, consumers trying to control impulsive spending should avoid consuming caffeinated beverages before shopping. [ABSTRACT FROM AUTHOR]

Although the positive effects of caffeine supplementation on individual and team-sports have been widely described, the literature evaluating the effect of caffeine supplementation on athletic performance in ice hockey players is almost non-existent. Therefore, the aim of the present study was to evaluate the effect of acute caffeine ingestion (3 mg/kg body mass). Thirteen elite adult ice hockey male players participated in this double-blind, randomized, counterbalanced, placebo-controlled crossover trial. A 35-m sprint, an agility test (Weave agility-slalom with puck), and a reaction test were performed twice in two separate days. On both occasions players ingested 330 ml of water with lemon isotonic drink (86 kcal/19 g of carbohydrates). On one of the days the drink included 3 mg/kg body mass of anhydrous caffeine. The randomization was performed by a researcher who was not involved in the register of main outcomes. No differences were found between the placebo and the caffeine condition for the 35-m sprint (4.223 vs. 4.188 s respectively, P = 0.516), Weave agility test (22.492 vs. 22.341 s respectively, P = 0.534) and reaction test (4.869 vs. 4.837 s respectively, P = 0.570). When analyzing individual results, three players showed improvements in the 35-m sprint while two showed decreases in performance after ingesting caffeine. Caffeine consumption did not improve athletic performance in ice hockey players. Clinicaltrial.gov (NCT05170139). [ABSTRACT FROM AUTHOR]

The study aimed to examine the combined effects of caffeine and aerobic exercise on leptin levels and some indices of insulin resistance in diabetics Thirty-two males with type 2 diabetes participated in a quasi-experimental and double-blind design. All participants were divided into four homogeneous groups of 8 individuals, including placebo (P), caffeine supplementation (C), aerobic training (AT), and aerobic training and caffeine (AT + C). The design protocol included eight weeks of aerobic exercise and caffeine consumption. Blood samples were taken to measure serum levels of leptin, glucose, insulin, HbA1c, HOMA-IR, and insulin sensitivity (QUICKI) indices at two phases. Data were analyzed by repeated measure ANOVA, Bonferroni posthoc, and independent T-test at a significant level of α ≤ 0.05. The results showed that the levels of leptin, glucose, insulin, HbA1c, and HOMA-IR in the three intervention groups significantly decreased compared to the placebo group (P = 0.001). In addition, QUICKI was significantly increased in the three groups of caffeine (C), aerobic training (AT), and aerobic training + caffeine (AT + C) compared to the placebo group (P = 0.001). Also, the AT+C group has double effects on the investigated indices compared to the caffeine (C) group (P = 0.001). Regular aerobic exercise and caffeine supplementation may be more effective treatments for improving insulin resistance indicators associated with type 2 diabetes. [ABSTRACT FROM AUTHOR]

The Adenosine A2A Receptor, ADORA2A, is a protein-coding gene that plays a crucial role in neuromodulatory functions. High expression of the A2A receptor in human brain cells is one of the known stress biomarkers in the human brain. Furthermore, a high dose of caffeine can cause brain diseases like stroke and dementia. However, the effect of a high dose of caffeine on ADORA2A gene expression in human brain cells has never been investigated. Therefore, we hypothesized that caffeine might induce stress through an increased intracellular H2O2 level, which overexpresses ADORA2A in brain cells. First, when A172 human brain cells were incubated with various concentrations of caffeine, the caffeine-treated A172 cells showed a significantly higher ADORA2A expression level than the no caffeine-treated control sample. Second, when A172 human brain cells were treated with 0 µM caffeine and 20 µM caffeine, the 20 µM caffeine sample had a 3-fold increase in its H2O2 levels, demonstrating that caffeine increases intracellular H2O2 levels in A172 cells. Third, 30 µM and 50 µM of H2O2 treatment significantly increased the ADORA2A expression level, indicating that a higher H2O2 concentration leads to a higher ADORA2A expression level. Overall, we found that high doses of caffeine significantly augmented the ADORA2A expression levels through increased intracellular H2O2 in human brain cells. The application of this novel molecular mechanism may contribute to the development of therapeutic drugs for caffeine-induced stress in human brain cells.. [ABSTRACT FROM AUTHOR]

Caffeine has a stimulating effect on the central nervous system, which can reduce fatigue and drowsiness. In addition, it has been shown to improve sports performance. In this current study, researchers used a randomized, placebo-controlled single-blind parallel groups trial to investigate the effects of caffeine on the sprint performance of male university football players aged 18 to 25 years in the Multan zone of South Punjab, Pakistan. A total of 120 players were divided into four groups of 30 each, with each group receiving a different dose of caffeine in capsule form. Group A received 3 mg-kg-1, Group B received 6 mg-kg-1 and Group C received 9 mg-kg-1, while Group D was given a placebo 0mg-kg-1 . Sprint performance were measured through 20m Sprint test before and after the administration of caffeine and data analysis was conducted using GraphPad Prism version 6.0 software, with statistical tests like paired sample ‘‘t’’-test, ANOVA and Pearson correlation being applied to determine the relationship of each dose of caffeine on sprint performance. In our study, all three study groups 3, 6 and 9 mg/kg-1 presented conspicuous effects of caffeine on the 20-m sprint test. Overall results of this study showed that high doses 9 mg/kg-1 had prominent effects on the Sprint performance of university football players. Pearson correlation coefficient results showed that there was a positive significant correlation between Group B 6mg Pre and Group C 9mg Post. Moreover, high doses of caffeine do more to improve the sprint performance of university football players. [ABSTRACT FROM AUTHOR]

Rationale: Caffeine is the most consumed stimulant worldwide, and there is great interest in understanding its neurophysiological effects. Resting-state electroencephalography (EEG) studies suggest that caffeine enhances arousal, which suppresses the spectral power of alpha frequencies associated with reduced alertness. However, it is unclear whether caffeine's neurophysiological effects vary across the human menstrual cycle. Objective: The objective of our study was to test whether caffeine's effect on EEG activity differs across the human menstrual cycle. Methods: Fifty-six female participants were randomly assigned to complete the experiment while in either their menstrual (n = 21), follicular (n = 19), or luteal (n = 16) phase. Each participant completed two study sessions in the same menstrual phase, approximately 1 month apart, during which they were administered either a caffeine pill (200 mg, oral) or a placebo pill in a counterbalanced order using a randomized double-blinded procedure. We measured their eyes-closed resting-state EEG approximately 30 min after pill administration and conducted a spectral power analysis at different frequency bands. Results: Caffeine reduced EEG power in the alpha1 frequency band (8–10 Hz), but only for participants who self-reported higher weekly caffeine consumption. Importantly, caffeine's effects did not differ by menstrual phase. Conclusions: We conclude that when studying caffeine's effects on resting-state EEG, participants' baseline caffeine consumption is more influential than their menstrual cycle phase. This study has important implications for the inclusion of menstruating individuals in neurophysiological studies of caffeine. [ABSTRACT FROM AUTHOR]

Aims: Osteoporosis is a metabolic bone disease characterized by low bone mass and deteriorated bone tissue. There is ongoing debate about the effect of caffeine intake on bone metabolism due to inconsistent study results. This study aimed to assess the association between caffeine intake and bone mineral density (BMD). Methods: This single center cross-sectional study, prospectively enrolled postmenopausal women aged between 41 and 65 years who underwent bone mineral density measurement by dual-energy X-ray absorptiometry (DXA) at the lumbar spine and femoral neck. Caffeine intake was estimated using a food frequency questionnaire (FFQ) and a caffeine-specific FFQ. Patients consuming more than 260 mg/day caffeine were classified as high consumers. Results: The study included 80 subjects (mean age: 57.1±5.6 years). Daily caffeine intake was 229.7±119.5 mg, and 36.3% (n=29) of the patients was classified as high consumers. The mean total T-score was -1.4±0.9 at the lumbar spine and -1.7±0.9 at femoral neck. High and low caffeine consumers had similar mean total T-score at the lumbar spine (-1.4±1.1 vs. -1.4±0.8, p=0.849). However, femoral neck mean T-score was significantly lower in high caffeine consumers (-2.0±0.9 vs. -1.5±0.7, p=0.033). The amount of daily caffeine intake showed a negative, moderate correlation with femoral neck T-score (r=-0.251, p=0.025). Conclusions: The results of this study suggest that higher caffeine intake may be associated with lower T-scores on DXA of the femoral neck. [ABSTRACT FROM AUTHOR]

The ergogenic effects of caffeine supplementation on repeated-sprint ability (RSA) have produced equivocal results. This study aimed to examine the effects of 200 mg of caffeine during repeated-sprint running on heart rate (HR), rating of perceived exertion (RPE), blood lactate (BLa) concentration, and sprint time (ST). Thirty-two individuals (males: n = 17, females: n = 15; age: 22 ± 1 years) participated in the study. The study followed a double-blind, randomized, placebo-controlled, crossover design, in which each participant ingested 200 mg of caffeine or placebo on separate visits 60 minutes prior to repeated-sprinting exercise. The repeated-sprint protocol consisted of three sets of six maximal-effort 30-meter sprints with 20 seconds and 5 minutes of active recovery in between sprints and sets, respectively. During each set, HR, RPE, BLa, and ST were recorded. Caffeine supplementation did not significantly (set 1: p = 0.535; set 2: p = 0.602; set 3: p = 0.189) impact HR during exercise. Similarly, RPE was not statistically (p = 0.052) altered between conditions during any of the sprint sets. The caffeine trials elicited greater BLa values after all three sets compared to the placebo trials (p < 0.001). Moreover, the caffeine trials demonstrated significantly reduced total STs during all sets compared to the placebo trials (p < 0.001). Thus, our findings suggested that 200 mg of caffeine supplementation elicited an increase in RSA in young, healthy non-athletes. These findings are accompanied by a blunted perceived exertion relative to an increase in exercise intensity during repeated-sprint exercise. [ABSTRACT FROM AUTHOR]

The placebo effect of caffeine has been poorly investigated in endurance exercise. Therefore, the aim of this study was to analyze the placebo effect of caffeine on 4 km running performance in amateur runners. Twenty-two healthy and recreational male runners (25.5 ± 8.4 yrs; 75.0 ± 7.1 kg; 173.7 ± 6.3 cm) underwent a deceptive experimental design consisting of three different sessions: a) control (CON) in which participants did not ingest any substance; b) placebo (PLA) in which participants ingested a capsule filled with maltodextrin but they were informed that they would receive caffeine; c) caffeine (CAF) in which participants were informed that they would receive caffeine and actually received caffeine. After 60 min for substances absorption, participants performed a 4-km test and they completed the distance as fast as possible. The time employed to cover the distance was lower in PLA (17.4 ± 1.5 min) and CAF (17.4 ± 1.4 min) than CON sessions (18.6 ± 2.8 min; P<0.05). There were no differences in the 4-km times between PLA and CAF (P>0.05) and no differences were reported between treatments for RPE (P>0.05). In conclusion, there was a placebo effect of caffeine on a 4-km maximal running trial which entailed that believing to have ingested caffeine improved performance to a similar extent than actually receiving caffeine. Therefore, the expectancy induced by caffeine may be one of the mechanisms behinds the ergogenic effect of this stimulant on endurance exercise. [ABSTRACT FROM AUTHOR]

Caffeine may impact post-exercise heart rate variability (HRV); although, studies have yielded inconsistent findings. We examined the effects of low dose caffeine on post-exercise HRV. Healthy, college-aged adults [n = 18; age: 22.1 ± 2.6 years; BMI: 26.9 ± 4.3 kg/m2; estimated maximal oxygen consumption (VO2max): 45.1 ± 8.3 ml·kg-1·min-1] participated in a repeated-measures, double-blind, placebo-controlled trial. During the experimental trials, participants were fitted with a heart rate monitor and a mouthpiece with a one-way nonrebreathing valve and then rested for 10 min during baseline HRV and expired gas assessments. Participants chewed either caffeine (~170mg) or placebo gum for 5 min. Following expectoration and a 5 min warmup, participants walked on a treadmill for 20 min at 60% of estimated VO2max and then rested for 30 min. HRV indices were calculated from 10 min measurements during baseline and post-exercise (post 1, 2, and 3). A main effect of treatment was found for standard deviation of RR intervals (SDNN), absolute power of low frequency band (LF), absolute power of high frequency band (HF), and the standard deviation perpendicular to the line-of-identity in Poincaré plot (SD1) (p < 0.05). Further, a trend for higher root mean square of successive RR interval differences (RMSSD) with caffeine was observed (p = 0.066). Post hoc t-tests revealed that post-exercise SDNN, LF, HF, and SD1 were higher with caffeine compared to placebo (p = 0.012). Results demonstrated that low dose caffeine did not delay the recovery of HRV indices reflective of parasympathetic nervous system activity following an acute bout of moderate exercise. [ABSTRACT FROM AUTHOR]

Background: In this study, we evaluate the available evidence regarding caffeine communication and its effect on cognitive function in people with ADHD. This systematic review examined various articles on this topic. Methods: In this systematic review, the selection of studies was carried out using the PubMed, Scopus databases, with a focus on articles published from 2000 to 2024. The search utilized keywords and MeSH terms such as "attention deficit disorder with hyperactivity" (ADHD) and "caffeine." Specifically, randomized control trial articles that investigated the use of caffeine as an intervention for individuals with ADHD were included in the present study. The comparison was made between participants who received caffeine as an intervention and those who did not, in order to assess the potential impact of caffeine on individuals with ADHD. Result: The research initially encompassed 121 articles containing 52 file attachments, identifying 2 final studies conducted in the USA and UK between 2019 and 2020. The studies reported using caffeine as an intervention, with a dosage of 2mg/kg for children aged 6-17 and 4mg/kg for adults aged 19-47. Specifically, the study by Kahathuduwa et al., involved 6 children, while the study by Hampsey et al., involved 27 adults. The findings from the studies indicated that the combination of caffeine and L-Theanine demonstrated improvements in Cognition composite, 11.4(p = 0.040). points greater than the mean cognition composite in placebo for children, and a decrease in the mean count of microsaccades in adults, had a 0.22(p:0.00027) decreasing effect In comparison with control group. Both studies were deemed to have acceptable methodological quality. Conclusion: This systematic review showed that caffeine supplementation could be a beneficial intervention in this disorder, however further research is needed to complete our view of this valuable field. [ABSTRACT FROM AUTHOR]