Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show?

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.

Creatine supplementation and endurance performance: surges and sprints to win the race.

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.

[Nutritional labeling and amino acid profile in high protein Chilean dairy products: a new alternative for health and sports]. / Etiquetado nutricional y perfil de aminoácidos en lácteos chilenos altos en proteína: nueva alternativa para la salud y el deporte.

INTRODUCTION: Introduction: protein is an essential nutrient that can be obtained through different food sources. In recent years, a growing development in the food industry of dairy products with higher protein content has emerged in the national market. Métodos: the present work analyzed the nutritional information, protein content, and amino acid profile of high protein yogurts. Five main brands of high-protein yogurt (PY) were selected, as was a sample of regular yogurt (RY), and one of whey protein isolate (WP), which underwent a proximal analysis and amino acid profile by high-performance liquid chromatography (HPLC). Results: it was observed that the protein content of the analyzed YP ranged between 7.2 and 15.1 g/portion, representing 6.8 % to 11 % of total content, twice the content of YBAT (3,4 %). Regarding carbohydrates and fats, these were found to range between 6.25 and 13.5 g/serving and 0.9 and 5.3 g/serving, respectively. Leucine content of the PY varied between 0.6 and 1.5 g/portion, which was higher than RY (0.3 g/portion) and lower than WP (2.2 g/portion). The sum of essential amino acids was found to be between 3 and 6.9 g/portion in PY, 1.7 g/serving y 8.5 g/serving in WP. Conclusion: these results show that PYs are a good alternative to promote a correct protein intake, similar to proteins for sports use, so their recommendation could be useful to promote consumption in different populations according to their needs.

INTRODUCCIÓN: Introducción: la proteína es un nutriente esencial que se puede obtener a través de diferentes fuentes alimentarias . En los últimos años, un creciente desarrollo de la industria alimentaria de productos lácteos con mayor aporte en proteínas ha surgido en el mercado nacional. Métodos: el presente trabajo analizó la información nutricional, el contenido proteico y el perfil de aminoácidos de una serie de yogures altos en proteína. Se seleccionaron 5 principales marcas de yogures altos en proteína (YP), una muestra de yogur batido (YBAT) y una de proteina de suero de leche aislado (WP) a las que se realizó un análisis proximal y un perfil de aminoácidos por cromatografía líquida de alto rendimiento (HPLC). Resultados: se pudo observar que el contenido de proteína de los YP analizados varió entre 7,2-15,1 g/porción, lo que representa del 6,8 al 11 % del contenido total, el doble del contenido del YBAT (3,4 %). Respecto a los hidratos de carbono y grasas, estos se encontraron entre 6,25 y 13,5 g/porción y 0,9 y 5,3 g/porción, respectivamente. El contenido de leucina de los YP varió entre 0,6 y 1,5 g/porción, con valores superiores a los de los YBAT (0,3 g/porción) e inferiores a los de las WP (2,2 g/porción). La suma de aminoácidos esenciales se encontró entre 3 y 6,9 g/porción en los YP, en 1,7 g/porción en los YBAT y 8,5 g/porción en las WP. Conclusión: estos resultados demuestran que los YP son una buena alternativa para promover una correcta ingesta proteica, semejante a las proteínas de uso deportivo, por lo que su recomendación podría ser útil para promover su consumo en diferentes poblaciones según sus necesidades.

Ethnicity and Health: Experience with an Urban Mapuche Health Program from the Perspective of Key Actors.

This article explores the relationships and tensions between ethnicity and health, describing the perspectives of various social actors on a Mapuche clinic in the context of a national health program. A qualitative methodology was used to carry out this case study of the Mapuche clinic "La Ruka," located in an urban area of the Metropolitan Region of Chile. The study analyzes the narratives of traditional health practitioners (including a machi, lawentuchefe, lonko, and intercultural facilitator), consumers, conventional healthcare professionals, and local health authorities and community leaders who share a physical, political, and symbolic space around the Mapuche health experience. The systemization of experiences method was applied to the data, acquired through nonparticipant observation, individual interviews, and focus groups. The results suggest that this healthcare experience is highly valued by its protagonists. However, there is a tension surrounding cultural diversity programs that recognize non-Western approaches to healing, such as indigenous practices. This study examines the health-related, cultural, and political tensions involved in projecting indigenous traditions into a homogenizing space such as healthcare in a multicultural neoliberalism system.