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Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show?
Antonio, J, Newmire, DE, Stout, JR, Antonio, B, Gibbons, M, Lowery, LM, Harper, J, Willoughby, D, Evans, C, Anderson, D, et al
Journal of the International Society of Sports Nutrition. 2024;(1):2323919
Abstract
Caffeine is a popular ergogenic aid that has a plethora of evidence highlighting its positive effects. A Google Scholar search using the keywords "caffeine" and "exercise" yields over 200,000 results, emphasizing the extensive research on this topic. However, despite the vast amount of available data, it is intriguing that uncertainties persist regarding the effectiveness and safety of caffeine. These include but are not limited to: 1. Does caffeine dehydrate you at rest? 2. Does caffeine dehydrate you during exercise? 3. Does caffeine promote the loss of body fat? 4. Does habitual caffeine consumption influence the performance response to acute caffeine supplementation? 5. Does caffeine affect upper vs. lower body performance/strength differently? 6. Is there a relationship between caffeine and depression? 7. Can too much caffeine kill you? 8. Are there sex differences regarding caffeine's effects? 9. Does caffeine work for everyone? 10. Does caffeine cause heart problems? 11. Does caffeine promote the loss of bone mineral? 12. Should pregnant women avoid caffeine? 13. Is caffeine addictive? 14. Does waiting 1.5-2.0 hours after waking to consume caffeine help you avoid the afternoon "crash?" To answer these questions, we performed an evidence-based scientific evaluation of the literature regarding caffeine supplementation.
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The Effect of Creatine Nitrate and Caffeine Individually or Combined on Exercise Performance and Cognitive Function: A Randomized, Crossover, Double-Blind, Placebo-Controlled Trial.
Mabrey, G, Koozehchian, MS, Newton, AT, Naderi, A, Forbes, SC, Haddad, M
Nutrients. 2024;(6)
Abstract
This study examined the effect of creatine nitrate and caffeine alone and combined on exercise performance and cognitive function in resistance-trained athletes. In a double-blind, randomized crossover trial, twelve resistance-trained male athletes were supplemented with 7 days of creatine nitrate (5 g/day), caffeine (400 mg/day), and a combination of creatine nitrate and caffeine. The study involved twelve resistance-trained male athletes who initially provided a blood sample for comprehensive safety analysis, including tests for key enzymes and a lipid profile, and then performed standardized resistance exercises-bench and leg press at 70% 1RM-and a Wingate anaerobic power test. Cognitive function and cardiovascular responses were also examined forty-five minutes after supplementation. Creatine nitrate and caffeine that were co-ingested significantly enhanced cognitive function, as indicated by improved scores in the Stroop Word-Color Interference test (p = 0.04; effect size = 0.163). Co-ingestion was more effective than caffeine alone in enhancing cognitive performance. In contrast, no significant enhancements in exercise performance were observed. The co-ingestion of creatine nitrate and caffeine improved cognitive function, particularly in cognitive interference tasks, without altering short-term exercise performance. Furthermore, no adverse events were reported. Overall, the co-ingestion of creatine nitrate and caffeine appears to enhance cognition without any reported side effects for up to seven days.
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Caffeine Does Not Alter Performance, Perceptual Responses, and Oxidative Stress After Short Sprint Interval Training.
Bernardo, MF, Enes, A, Rezende, EF, Okuyama, AR, Alves, RC, de Andrade, M, Macedo, ACG, de Barros, MP, Candow, DG, Forbes, SC, et al
International journal of sport nutrition and exercise metabolism. 2024;(3):179-187
Abstract
Despite the abundance of research investigating the efficacy of caffeine supplementation on exercise performance, the physiological and biochemical responses to caffeine supplementation during intermittent activities are less evident. This study investigated the acute effects of caffeine supplementation on measures of exercise performance, ratings of perceived exertion, and biomarkers of oxidative stress induced by an acute bout of sprint interval training. In a randomized crossover design, 12 healthy males (age: 26 ± 4 years, height: 177.5 ± 6 cm, body mass: 80.7 ± 7.6 kg) ingested 6 mg/kg of caffeine or placebo 60 min prior to performing sprint interval training (12 × 6 s "all-out sprints" interspersed by 60 s of rest). Performance scores and ratings of perceived exertion were assessed after every sprint. Blood samples were collected before supplementation, prior to and following each sprint, and 5 and 60 min after the last sprint. Caffeine had no effect on any performance measures, ratings of perceived exertion, or biomarkers of oxidative stress (p > .05). In conclusion, caffeine supplementation does not improve performance or decrease oxidative stress after an acute bout of sprint interval training.
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Carbohydrates and Endurance Exercise: A Narrative Review of a Food First Approach.
Naderi, A, Gobbi, N, Ali, A, Berjisian, E, Hamidvand, A, Forbes, SC, Koozehchian, MS, Karayigit, R, Saunders, B
Nutrients. 2023;(6)
Abstract
Carbohydrate (CHO) supplements such as bars, gels, drinks and powders have become ubiquitous as effective evidence-based CHO sources that improve endurance exercise performance. However, athletes are increasingly turning to more cost-effective 'food-first' approaches for CHO ingestion to improve exercise performance. Mixed CHO foods including cooked lentils, oats, honey, raisins, rice, and potatoes are all effective pre-exercise CHO food sources. Caution is advised when selecting some of these foods as a primary CHO source, as some athletes may be prone to gastrointestinal discomfort-especially regarding those foods where the quantities required for recommended CHO intake may be voluminous (e.g., potatoes). Palatability may be another barrier to the ingestion of some of these CHO-rich foods. Although most of these CHO-rich foods appear effective for exercise performance or recovery when consumed pre- and post-exercise, not all are viable to ingest during exercise due to difficulties in the quantities required, transport, and/or gastrointestinal discomfort. Raisins, bananas and honey may be particularly useful CHO foods for consumption during exercise, as they are easily transportable. Athletes should trial CHO food sources before, during and/or following training before implementation during competition.
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Creatine supplementation and endurance performance: surges and sprints to win the race.
Forbes, SC, Candow, DG, Neto, JHF, Kennedy, MD, Forbes, JL, Machado, M, Bustillo, E, Gomez-Lopez, J, Zapata, A, Antonio, J
Journal of the International Society of Sports Nutrition. 2023;(1):2204071
Abstract
Creatine supplementation is an effective ergogenic aid to augment resistance training and improve intense, short duration, intermittent performance. The effects on endurance performance are less known. The purpose of this brief narrative review is to discuss the potential mechanisms of how creatine can affect endurance performance, defined as large muscle mass activities that are cyclical in nature and are >~3 min in duration, and to highlight specific nuances within the literature. Mechanistically, creatine supplementation elevates skeletal muscle phosphocreatine (PCr) stores facilitating a greater capacity to rapidly resynthesize ATP and buffer hydrogen ion accumulation. When co-ingested with carbohydrates, creatine enhances glycogen resynthesis and content, an important fuel to support high-intensity aerobic exercise. In addition, creatine lowers inflammation and oxidative stress and has the potential to increase mitochondrial biogenesis. In contrast, creatine supplementation increases body mass, which may offset the potential positive effects, particularly in weight-bearing activities. Overall, creatine supplementation increases time to exhaustion during high-intensity endurance activities, likely due to increasing anaerobic work capacity. In terms of time trial performances, results are mixed; however, creatine supplementation appears to be more effective at improving performances that require multiple surges in intensity and/or during end spurts, which are often key race-defining moments. Given creatines ability to enhance anaerobic work capacity and performance through repeated surges in intensity, creatine supplementation may be beneficial for sports, such as cross-country skiing, mountain biking, cycling, triathlon, and for short-duration events where end-spurts are critical for performance, such as rowing, kayaking, and track cycling.
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"Heads Up" for Creatine Supplementation and its Potential Applications for Brain Health and Function.
Candow, DG, Forbes, SC, Ostojic, SM, Prokopidis, K, Stock, MS, Harmon, KK, Faulkner, P
Sports medicine (Auckland, N.Z.). 2023;(Suppl 1):49-65
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Abstract
There is emerging interest regarding the potential beneficial effects of creatine supplementation on indices of brain health and function. Creatine supplementation can increase brain creatine stores, which may help explain some of the positive effects on measures of cognition and memory, especially in aging adults or during times of metabolic stress (i.e., sleep deprivation). Furthermore, creatine has shown promise for improving health outcome measures associated with muscular dystrophy, traumatic brain injury (including concussions in children), depression, and anxiety. However, whether any sex- or age-related differences exist in regard to creatine and indices of brain health and function is relatively unknown. The purpose of this narrative review is to: (1) provide an up-to-date summary and discussion of the current body of research focusing on creatine and indices of brain health and function and (2) discuss possible sex- and age-related differences in response to creatine supplementation on brain bioenergetics, measures of brain health and function, and neurological diseases.
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Author's reply: Letter to the Editor: Double counting due to inadequate statistics leads to false-positive findings in "Effects of creatine supplementation on memory in healthy individuals: a systematic review and meta-analysis of randomized controlled trials".
Prokopidis, K, Giannos, P, Triantafyllidis, KK, Kechagias, KS, Forbes, SC, Candow, DG
Nutrition reviews. 2023;(11):1497-1500
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Taurine supplementation enhances anaerobic power in elite speed skaters: A double-blind, randomized, placebo-controlled, crossover study.
Buzdağlı, Y, Eyipınar, CD, Öget, F, Şıktar, E, Forbes, SC, Tekin, A
Biology of sport. 2023;(3):741-751
Abstract
Taurine (2-aminoethanesulfonic acid) is a semi-essential sulphur-containing amino acid abundant in skeletal muscle. Taurine supplementation is popular among athletes and has been purported to enhance exercise performance. This study aimed to investigate the ergogenic effects of taurine supplementation on anaerobic (Wingate; WanT) performance, blood lactate, ratings of perceived exertion (RPE), and countermovement vertical jump (CMJ) in elite athletes. For this study, randomized, double-blind, placebo-controlled crossover designs were used. Thirty young male speed skaters were randomly assigned to either taurine (TAU; single dose of 6 g) or placebo (PLAC; single dose of 6 g) 60 minutes before testing. Following a 72-hour washout, period participants completed the opposite condition. TAU improved peak (Δ% = 13.41, p < 0.001, d = 1.71), mean (Δ% = 3.95, p = 0.002, d = 1.04), and minimum power output (Δ% = 7.89, p = 0.034, d = 0.48) compared to placebo. Further, RPE (Δ% = -10.98, p = 0.002, d = 0.46) was significantly lower following the WanT in the TAU condition compared to placebo. There were no differences between conditions for the countermovement vertical jump. In conclusion, acute TAU supplementation augments anaerobic performance in elite speed skaters.
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Effects of creatine supplementation on memory in healthy individuals: a systematic review and meta-analysis of randomized controlled trials.
Prokopidis, K, Giannos, P, Triantafyllidis, KK, Kechagias, KS, Forbes, SC, Candow, DG
Nutrition reviews. 2023;81(4):416-427
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Plain language summary
The brain requires a high amount of energy for cellular processes. Creatine, an organic acid obtained from the diet (primarily from red meat and seafood) or synthesised endogenously in the liver, the kidneys, and the brain,2 is an important molecule for energy production. The aim of this study was to assess the effects of creatine supplementation vs placebo on memory performance in healthy humans. This study was a systematic review and meta-analysis of ten studies – two studies were excluded from meta-analysis. Results showed that measures of memory following creatine supplementation, compared with placebo, were improved. These benefits were more robust in older adults (66–76 years). Authors concluded that more research is needed utilising a rigorous, large, long-term randomised clinical trial to elucidate the potential effect of creatine monohydrate supplementation on memory performance.
Abstract
CONTEXT From an energy perspective, the brain is very metabolically demanding. It is well documented that creatine plays a key role in brain bioenergetics. There is some evidence that creatine supplementation can augment brain creatine stores, which could increase memory. OBJECTIVE A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to determine the effects of creatine supplementation on memory performance in healthy humans. DATA SOURCES The literature was searched through the PubMed, Web of Science, Cochrane Library, and Scopus databases from inception until September 2021. DATA EXTRACTION Twenty-three eligible RCTs were initially identified. Ten RCTs examining the effect of creatine supplementation compared with placebo on measures of memory in healthy individuals met the inclusion criteria for systematic review, 8 of which were included in the meta-analysis. DATA ANALYSIS Overall, creatine supplementation improved measures of memory compared with placebo (standard mean difference [SMD] = 0.29, 95%CI, 0.04-0.53; I2 = 66%; P = 0.02). Subgroup analyses revealed a significant improvement in memory in older adults (66-76 years) (SMD = 0.88; 95%CI, 0.22-1.55; I2 = 83%; P = 0.009) compared with their younger counterparts (11-31 years) (SMD = 0.03; 95%CI, -0.14 to 0.20; I2 = 0%; P = 0.72). Creatine dose (≈ 2.2-20 g/d), duration of intervention (5 days to 24 weeks), sex, or geographical origin did not influence the findings. CONCLUSION Creatine supplementation enhanced measures of memory performance in healthy individuals, especially in older adults (66-76 years). SYSTEMATIC REVIEW REGISTRATION PROSPERO registration no. 42021281027.
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Resistance Exercise and Creatine Supplementation on Fat Mass in Adults < 50 Years of Age: A Systematic Review and Meta-Analysis.
Candow, DG, Prokopidis, K, Forbes, SC, Rusterholz, F, Campbell, BI, Ostojic, SM
Nutrients. 2023;15(20)
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Plain language summary
Increased body fat in young adults is leading to the development of health complications in later life. The use of resistance exercise in combination with creatinine has been shown to decrease body fat in people over the age of 55. However, it is unclear as to whether this combination would have the same result in those under 55 years. This systematic review and meta-analysis of 12 randomised control trials with 266 individuals aimed to review the data on the use of creatinine and resistance exercise in individuals less than 55 years of age. The results showed that compared to resistance exercise alone, creatinine supplementation did not impact absolute fat mass, but did decrease body fat percentage over time. When in combination with resistance exercise individuals had a very small but significant reduction in body fat percentage, but absolute fat mass remained unaffected. It was concluded that in adults under the age of 50, a combination of resistance exercise and creatinine decreased body fat percentage but had no effect on absolute fat mass. This study could be used by healthcare professionals to understand that creatinine and resistance exercise may have a very small benefit on body fat percentage, however the cost of supplementation may outweigh the benefits.
Abstract
The combination of resistance exercise and creatine supplementation has been shown to decrease body fat percentage in adults ≥ 50 years of age. However, the effect on adults < 50 years of age is currently unknown. To address this limitation, we systematically reviewed the literature and performed several meta-analyses comparing studies that included resistance exercise and creatine supplementation to resistance exercise and placebo on fat mass and body fat percentage Twelve studies were included, involving 266 participants. Adults (<50 years of age) who supplemented with creatine and performed resistance exercise experienced a very small, yet significant reduction in body fat percentage (-1.19%, p = 0.006); however, no difference was found in absolute fat mass (-0.18 kg, p = 0.76). Collectively, in adults < 50 years of age, the combination of resistance exercise and creatine supplementation produces a very small reduction in body fat percentage without a corresponding decrease in absolute fat mass.