Marcin Osowski, Paweł Błażej Szewczyk, Bartłomiej Dorożyński, Ewa Szura

Supplementation for athletes – part 2. Caffeine

2024-08-26

Caffeine is one of the most popular ergogenic agents used by athletes at various levels of training to improve physical performance and exercise capacity. Numerous studies have shown that caffeine supplementation can be used in a wide range of sports, such as running, cycling, swimming, team sports, and strength or figure sports. Caffeine supplementation can result in an improvement in sports performance by several percent. Caffeine consumption can increase alertness levels, improve reaction time and concentration, performance or muscle strength. In addition, supplementation can delay the onset of fatigue, as well as reduce the perception of the severity of the exercise performed. Caffeine’s main mechanism of action is based on blocking adenosine A1 and A2A receptors, present throughout the brain.

As a result, there is an increase in the secretion of neurotransmitters (norepinephrine, dopamine, serotonin, glutamate, gamma-aminobutyric acid (GABA) and acetylcholine). Caffeine also inhibits phosphodiesterase activity, which in turn leads to the accumulation of intracellular cyclic adenosine monophosphate (cAMP), which is involved in many metabolic processes. One of the expected effects of caffeine supplementation is to maximize the rate of lipolysis, resulting in an increase in the availability of free fatty acids, which could then potentially contribute to a reduction in the rate of muscle glycogen utilization during exercise. The effect of caffeine on calcium ion release and uptake remains unclear. It is assumed that the optimal time to take caffeine is between 30 and 60 minutes before the start of exercise, and the recommended dose is between 3 and 6 milligrams per kilogram of an athlete’s body weight. It is worth, however, to note  that there are many forms of caffeine intake (e.g., chewing gum, drinks, capsules), which are characterized by different rates of availability of the active compound, and as a result, reaching the peak concentration of caffeine in the blood serum and achieving the supplementation effects. Caffeine is also present in many conventional foods, such as tea, coffee, yerba mate, cocoa, chocolate and energy drinks, in which it does not occur naturally, but is added. An aspect that has a significant impact on the effectiveness of caffeine use is the genetic variation associated with two single nucleotide polymorphisms, CYP1A2 and ADORA2A. CYP1A2 is responsible for coding for cytochrome P450 1A2, the enzyme responsible for about 95% of caffeine metabolism. Individuals with the AA genotype are predisposed to produce more of this enzyme and therefore metabolize caffeine faster than those with the AC and CC genotypes. Caffeine consumption by individuals characterized by the CC genotype may be associated with a decrease in exercise capacity and performance, despite the use of recommended supplementation doses. A polymorphism within ADORA2A, the gene encoding the A2A adenosine receptor subtype, is responsible for caffeine sensitivity. Individuals with the TT allele exhibit greater sensitivity to caffeine, compared to those with the CT or CC genotype, which are often characterized as “unresponsive” to supplementation. Caffeine use-especially when taken in excessive doses-can cause side effects such as sleep disturbances, excessive agitation, gastrointestinal problems and muscle tremors. Further well-designed studies are needed, particularly with women, evaluating the effects of caffeine on physical performance in specific conditions and sports. Priority should be given to the principle of “first, do no harm”, and supplementation should be planned in such a way that the potential benefits of caffeine consumption are not overshadowed by possible side effects.

Keywords: caffeine, sport nutrition, ergogenic aid, performance, genes.

© Farm Pol, 2024, 80(4): 267–277