The role of caffeine in sports supplementation


Caffeine, found in many everyday foods and beverages, is undoubtedly one of the most studied molecules for its potential effects on athletic performance. Once considered merely a stimulant for the nervous system, recent scientific findings suggest that caffeine may have broader effects.

Caffeina e integrazione sportiva
Recent research indicates that caffeine enhances performance not only indirectly (by stimulating the nervous system) but also directly through specific actionse. 

What is caffeine?

Chemically known as 1,3,7-trimethylxanthine, caffeine is an organic compound of plant origin, commonly found in coffee beans. However, it is also present in many other foods and beverages, naturally occurring in cocoa beans, tea leaves, guarana berries, kola nuts, and more. Average daily intake and primary sources vary by geographic region.

In the European Union, average daily caffeine intake ranges are:

  • Adults: 37-319 mg
  • Seniors (over 65 anni): 23-362 mg

How caffeine works

Caffeine primarily affects the nervous system by blocking the activity of adenosine, a neurotransmitter involved in sleep and wakefulness regulation. Produced by the nervous system during physical activity, adenosine binds to specific brain receptors, promoting sleepiness. Due to its molecular structure, which is similar to adenosine, caffeine can bind to adenosine receptors, inhibiting the fatigue signal.

Caffeine's performance-enhancing effects can also be attributed to its metabolic conversion into other molecules: paraxanthine, theobromine, and theophylline. According to recent studies, these metabolites enhance athletic performance through specific actions:

  • Paraxanthine (84%) stimulates lipolysis, increasing the concentration of glycerol and fatty acids in the blood. This boosts fatty acid oxidation, conserving glycogen stores (our carbohydrate reserves), which is significant for long-duration events.
  • Theobromine (12%) acts as a vasodilator, increasing blood flow to the muscles, thereby improving the supply of oxygen and nutrients. This can enhance endurance, strength, and recovery during and after exercise.
  • Theophylline (4%), relaxes the smooth muscles in the bronchi, improving respiratory function and, consequently, athletic performance.

* Acccording to recent studies (Kovacs et al., 1998; Coxe et al., 2002) plasma levels of free fatty acids increase by 5-10% after caffeine ingestion.

Potential effects of caffeine in athletes

The increasing number of athletes using caffeine to enhance performance has allowed for extensive study. 
Research suggests that caffeine can improve athletic performance in both strength/power sports and endurance sports*.
The increase in strength is attributed to greater calcium influx into the muscles, while the increase in endurance is linked to more efficient management of glycogen stores (a limiting factor in long-duration sports). The reduction in fatigue is connected to increased oxidative metabolism and caffeine’s analgesic (pain-reducing) effect.
However, no significant effects have been noted in events requiring sprints and bouts lasting between 15 seconds and 3 minutes.
Additionally, caffeine enhances precision and speed in sports requiring highly technical movements, such as tennis and golf*.

* Costill, 1978; Graham et al., 1995; Pasman et al., 1995; Trice et al., 1995; Coxe t al., 2002; Pencek et al., 2004.
* Kovacs et al, 2006; Horney et al., 2007

How, when and how much caffeine to take for performance

Caffeine is fully absorbed within about 45 minutes of ingestion. It is then distributed throughout the body, with its concentration halving over the next 3-6 hours. This wide time range reflects individual differences in metabolism. Dosage and timing of caffeine intake also vary widely. The EFSA (European Food Safety Authority) has set a safe limit of 200 mg of caffeine per single intake (an espresso contains about 80 mg) and a maximum daily limit of 400 mg.
In endurance sports, a safe and effective dose to achieve benefits without unwanted side effects is about 3 mg of caffeine per kg of body weight*.
For athletes who metabolize caffeine quickly, multiple small doses during performance (top-ups) are recommended, while those with longer-lasting effects may benefit from a single dose before performance.

* J Int Soc Sports Nutr 2021;18(1):1

Gel energetici con caffeina

Caffeine and carbohydrates

Initially, caffeine in sports supplementation was mainly found in pre-workout products used before gym sessions. Today, it is also used in endurance-specific products, such as energy gels for use during performance.

A study by the University of Birmingham* found that caffeine, when taken with glucose (a common ingredient in energy products), enhances the oxidation of exogenous carbohydrates more than carbohydrates alone. This higher oxidation rate is due to better intestinal absorption of glucose.
Research in this area continues.

* Yeo, 2005


  • Caffeine is the most widely used and studied stimulant in sports.
  • Numerous studies highlight caffeine’s ability to enhance sports performance through direct actions (effects on strength, endurance, speed, and precision) and indirect actions (reducing physical fatigue).
  • Combined intake of carbohydrates and caffeine appears to increase the oxidation of exogenous carbohydrates, potentially conserving muscle glycogen stores.
  • The optimal caffeine dosage and timing should be individually assessed, as the dose-response effect varies with individual metabolism.




- Casiraghi E. L’alimentazione prima dell’attività fisica. Scienza & Sport, 7:88-91; 2010.
- Costill D.L., Dalsky G.P., Fink W.J. Effects of caffeine ingestion on metabolism and exercise performance. Med Sci Sports Exercise. 1978.
- Yeo S.E., Jentjens R.L., Wallis G.A., Jeukendrup A.E. Caffeine increases exogenus carbohydrate oxidation during exercise. J Appl Physiol., 99(3): 844-50; 2005.
- Doherty, P.M. Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta-analysis. Scandinavian Journal of Medicine & Science in Sports; 15, 69; 2005.
- Doherty M, Smith P, Hughes M, Davidson R. Caffeine lowers perceptual response and increases power output during high-intensity cycling. J Sports Sci. luglio; 22(7): 637-43. 2004.



NOTE: The information provided is for informational purposes only and is not intended to replace the advice of your physician or healthcare professional. The information is intended for healthy individuals, and any dietary regimen or physical activity should be supervised by a competent professional according to Italian law. Enervit SpA assumes no responsibility, as the information is for informational purposes, and anyone interested in undertaking any dietary or physical activity program should consult their specialist.