Caffeine and Doping—What Have We Learned since 2004

摘要

Caffeine is a naturally occurring plant alkaloid and is found in plant constituents such as coffee and cocoa beans, tea leaves, guarana berries and the kola nut [ ]. It is added to a variety of foods, such as baked pastries, ice creams, sweets, and cola drinks. In energy drinks, caffeine is frequently combined with substances such as taurine and D-glucurono-γ-lactone [ ]. Moreover, it belongs to the most frequently used and consumed pharmacologic substances [ ]. Caffeine exerts a variety of effects on human physiology. Caffeine is absorbed rapidly in the gastrointestinal tract about 40 to 60 minutes after uptake peak plasma concentrations are reached [ ], and, after 3 to 5 hours, 50% has been excreted [ ]. As a lipophilic substance it is able to cross membranes such as the blood–brain barrier or placenta [ ]. Caffeine uptake results in ergogenic effects. In humans, caffeine stimulates the central nervous system, and in moderate doses increases alertness and reduces sleepiness [ ]. In sports, it has been shown that caffeine is ergogenic and improves athletic performance, especially endurance performance involved in sports such as running, swimming and cycling [ , ]. Here, its consumption has been shown to increase in the duration of the exercise or a decreased perception of exertion [ , ]. Moreover, the effects on anaerobic-based performance and strength performance have been demonstrated [ ]. These performing enhancing effects are also confirmed by the International Olympic Committee in its consensus statement on dietary supplements [ ]. Based on this information, it is not surprising that caffeine is present in a huge number of food supplements that are marketed for weight loss and sports performance [ ].