Caffeine’s easy accessibility and ergogenic (energy producing) effects are thought to have made it the most widely used stimulant worldwide. It is estimated that 90% of adults consume caffeine as a part of their normal diet.1 Caffeine can be found in coffee, tea, cola products, energy drinks/bars/gels, some vitamins/supplements, non-prescription medications (cough syrups and weight loss products) and even chocolate! Caffeine has been shown to increase mental alertness, improve mood, enhance reaction time and improve athletic performance.2
Caffeine is thought to work by increasing the amount of adrenaline that is released in the blood stimulating the release of free fatty acids, sparing muscle glycogen from fat or muscle tissue.3 Caffeine is classified as “ergogenic,” which means that it increases the ability for “work” output. Clinical studies investigating the effects of caffeine showed overall improved performance in athletes competing in endurance sports such as running, rowing, biking and swimming. One of the studies included in the analysis showed an increase in performance of 23.8 seconds for runners who used caffeine before an 8 kilometer run.4 Furthermore, evidence suggests that benefits occur at relatively low doses of caffeine, approximately 2-3 milligrams per kilogram, the equivalent of around 2 cups of coffee.
While there is evidence that caffeine may enhance athletic performance, disadvantages to caffeine consumption must also be considered. Side effects of caffeine include: anxiety, jitteriness, inability to focus, gastrointestinal (GI) upset, insomnia, irritability and potentially elevated heart rate.3 These side effects are typically more prominent at higher doses, greater than 9 milligram per kilogram (for the average 70kg/154 lb person, this would be equivalent to around 5-6 cups of coffee), but can also be seen at lower doses. Potentially serious heart rhythm alterations (arrhythmias) have been reported after very high doses of caffeine.2
Caffeine also is a known diuretic, meaning it causes an increase in urine production; this can affect hydration status, especially in athletes engaging in strenuous exercise. Another important factor to consider with caffeine is that of withdrawal when one abruptly stops the intake of caffeine. Symptoms of caffeine withdrawal including headache, fatigue, decreased energy, depressed mood and irritability, are not uncommon upon discontinuation of caffeine, even after relatively short periods of use.2
The use of caffeine in athletes continues to be a controversial topic. At one point, caffeine was included on the banned list of substances by the International Olympic Committee. However, the ruling has since changed, limiting urine caffeine concentrations to less than 12 mcg/ml, likely due to the widespread use of caffeine in everyday life. This limit generally allows for modest daily caffeine intake. Because caffeinated beverages have become so universal among people in general, normal daily consumption in athletes is seen as acceptable overall. However, use of high dose caffeine to artificially enhance athletic performance is viewed by many in the same category as other “performance-enhancing drugs”.
Caffeine Caveats
- Caffeine, even at small doses, can promote a stimulant effect on a person engaged in a strenuous activity or even at rest.
- Side effects of typical doses of caffeine can be increased heart rate or jitteriness, but larger doses can also lead to dangerous heart alterations.
- Even small doses of caffeine can increase urination which, particularly during long or strenuous activities (with or without hot, humid weather!), can lead to poor performance due to decreased hydration status. Try drinking more water to offset this side effect.
- “Caffeine withdrawal headaches” (along with other not-fun effects) can occur when one suddenly stops caffeine intake after using it for a long period of time. To avoid this, try slowly removing caffeine from your diet rather than going “cold turkey.”
Stacy Farry and Zackary McMullan, PharmD. 2016 Candidates and Kim Benner, PharmD, BCPS, FASHP, FPPAG. Kim Benner is a distance runner and current Volunteer Coordinator for the BTC. When she’s not running the streets of Birmingham, Kim is a clinical pharmacist at Children’s of Alabama, a Professor of Pharmacy Practice at Samford University and a mother of two non-running boys.
References:
Burke LM. Caffeine and Sports Performance. Appl Physiol Nutr Metab 2008;33(6):1319.Bordeaux B, Liberman HR. Benefits and risks of caffeine and caffeinated beverages. In: UpToDate, Post TW (Ed), UpToDate, Waltham, MA. (Accessed on September 15, 2015.)
Spriet LL, Graham TE. Caffeine and Exercise Performance. American College of Sports Medicine. http://www.acsm.org/docs/current-comments/caffeineandexercise.pdf
Bridge CA, Jones MA. The effect of caffeine ingestion on 8 km run performance in a field setting. Journal of Sports Science. 2006; 4 (433-9).