Supplement Overview
• Caffeine is a substance that occurs naturally in the leaves, nuts and seeds of a number of plants. It enjoys social acceptance and widespread use around the world.
• Major dietary sources of caffeine, such as tea, coffee, chocolate and cola drinks typically provide 30-100 mg of caffeine per serve, while some non-prescriptive medications contain 100-200 mg of caffeine per tablet.
• The recent introduction of caffeine (or guarana) to 'energy drinks', confectionery and sports foods/supplements has increased the opportunities for athletes to consume caffeine, either as part of their everyday diet or for specific use as an ergogenic aid (see Table 1).
• In 1 January 2004, caffeine was removed from the 2004 World Anti-Doping Agency Prohibited List, allowing athletes who compete in sports that are compliant with the WADA code to consume caffeine, within their usual diets or for specific purposes of performance, without fear of sanctions.
• Caffeine has numerous actions on different body tissues. The actions may vary between individuals and include both positive and negative responses. Effects include the mobilisation of fats from adipose tissue and the muscle cell, changes to muscle contractility, alterations to the central nervous system to change perceptions of effort or fatigue, stimulation of the release and activity of adrenaline, and effects on cardiac muscle.
• Recent evidence has changed our perspective on two of the widely promoted effects of caffeine:
1. Caffeine enhances endurance performance because it promotes an increase in the utilisation of fat as an exercise fuel and 'spares' the use of the limited muscle stores of glycogen
In fact, studies now show that the effect of caffeine on 'glycogen sparing' during sub-maximal exercise is short-lived and inconsistent - not all athletes respond in this way. Therefore, it is unlikely to explain the enhancement of exercise capacity and performance seen in prolonged continuous events and exercise protocols.
2. Caffeine-containing drinks have a diuretic effect and cause an athlete to become dehydrated.
In fact, small to moderate doses of caffeine have minor effects on urine losses or the overall hydration in people who are habitual caffeine users. In addition, caffeine-containing drinks such as tea, coffee and cola drinks provide a significant source of fluid in the everyday diets of many people.
• There is sound evidence that caffeine enhances endurance and provides a small but worthwhile enhancement of performance over a range of exercise protocols. These include short-duration high-intensity events (1-5 min), prolonged high-intensity events (20-60 min), endurance events (90 min + continuous exercise), ultra-endurance events (4 hours +), and prolonged intermittent high-intensity protocols (team and racquet sports). The effect on strength/power and brief sprints (10-20 sec) is unclear.
• The mechanism underpinning performance benefits is unclear, but it is likely to involve alterations to the perception of effort or fatigue, as well as direct effects on the muscle.
• Most studies of caffeine and performance have been undertaken in laboratories. Studies that investigate performance effects in elite athletes under field conditions or during real-life sports events are scarce and need to be undertaken before specific recommendations for caffeine supplementation protocols can be made.
• Traditional protocols for the use of caffeine involve the intake of caffeine one hour prior to the event, in doses equivalent to ~ 6 mg/kg (e.g. 300-500 mg for a typical athlete).
• There is new evidence, at least from studies involving prolonged exercise lasting longer than 60 minutes, that a variety of protocols of caffeine use can enhance performance. In particular, benefits have been seen with small-moderate levels of caffeine (1-3 mg/kg BM or 70-200 mg caffeine) taken before and/or throughout exercise, or towards the end of exercise when the athlete is becoming fatigued).
• Furthermore, these studies show that performance benefits do not increase with increases in the caffeine dose above 3 mg/kg. The use of larger doses of caffeine increases the risk of side-effects.
• There is considerable individual variability in the response to caffeine intake – some individuals will have a benefit from caffeine use, while others may experience no effect or side-effects from the same caffeine dose or protocol of use
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Table 1: Caffeine content of common foods and drinks.
Food or Drink
Serve
Caffeine Content (mg)
Instant coffee
250 ml cup
60 (12-169)a
Brewed coffee
250 ml cup
80 (40-110)a
Short black coffee/espresso
1 standard serve
107 (25-214)b
Starbucks Breakfast Blend brewed coffee
600 ml (Venti size)
415 (300-564)c
Iced coffee - Commercial Brands
500 ml bottle
30-200
Frappuccino
375 ml cup
90
Tea
250 ml cup
27 (9-51)a
Iced Tea
600 ml bottle
20-40
Hot chocolate
250 ml cup
5-10
Chocolate -milk
60 g
5-15
Chocolate - dark
60 g
10-50
Viking chocolate bar
60 g
58
Coca Cola
375 ml can
49
Pepsi Cola
375 ml can
40
Jolt soft drink
375 ml can
75
Red Bull energy drink
250 ml can
80
Red Eye Power energy drink
250 ml can
50
V Energy drink
250 ml can
50
Smart Drink - Brain fuel
250 ml can
80
Lift Plus energy drink
250 ml can
36
Lipovitan energy drink
250 ml can
50
Mother energy drink
500 ml can
160
AMP Energy (USA)
500 ml can
143
Spike Shotgun energy drink (USA)
500 ml can
350
Fixx Extreme Ultra shot
5 ml shot
400
Ammo energy shot (USA)
30 g
170
Jolt endurance shot (USA)
60 g
200
PowerBar caffeinated sports gel
40 g sachet
25
PowerBar double caffeinated sports gel
40 g sachet
50
PowerBar caffeinated gel blasts
60 g pouch (~9)
75
Gu caffeinated sports gel
32 g sachet
20
Carboshotz caffeinated sports gel
50 g sachet
80
PB speed sports gels
35 g sachet
40
PowerBar Performance bar with Acticaf
65 g bar
50
Extreme Sports beans - caffeine
28 g packet
50
Jolt caffeinated gum (USA)
1 stick
33
No Doz
1 tablet - Australia
1 tablet - USA
100
200
Excedrin Extra strength (USA)
1 tablet
65
*These values were gathered from a variety of sources including manufacturers’ information and nutrition databases (Centre for Science in the Public Interest;
Caffeine Content and USDA National Nutrient Database;
http://www.nal.usda.gov/fnic/foodcomp/search/); note that commercial brands may vary slightly from country to country.
a The caffeine content of tea and coffee varies widely, depending on the brand, the way that the individual makes their beverage, and the size of their mug or cup.
b Commercial samples bought from a variety of outlets (Desbrow B, Hughes R, Leveritt M, Scheelings, P. An examination of consumer exposure to caffeine from retail coffee outlets. Food Chem Toxicol. 2007;45: 1588-1592.
c Commercial samples bought from the same Starbucks outlet (McCusker RR, Goldberger BA, Cone E J. Caffeine content of specialty coffees. J Anal Toxicol 2003; 27: 520-522
Situations for Use in Sport
• Prior to and/or during prolonged endurance or intermittent sports, including team sports, as a training aid or competition aid.
• Prior to high-intensity events, as a training aid or competition aid.
Concerns Associated with Supplement Use
• We are aware that current caffeine intake practices of athletes are ad hoc and unsystematic with, at times, a lack of awareness of the potential for side-effects or negative outcomes from caffeine use, and a lack of awareness of emerging information about caffeine and sports performance.
• At higher levels of intake, caffeine has the potential to cause increases in heart rate, impairments or alterations of fine motor control and technique, and over-arousal (interfering with recovery and sleep patterns). Impairment of technique may affect the performance of a number of sports, and over-arousal may interfere with the ability to recover between training sessions, or multi-day competitions. These concerns add to the importance of finding the lowest effective dose of caffeine that can be used to achieve a performance enhancement.
• There may be interactions between caffeine and other supplements/nutrients used by athletes (e.g. bicarbonate, creatine, carbohydrate) that need to be explored in terms of performance outcomes and potential side-effects.
• Although evidence of specific health problems is equivocal, long-term intake of large amounts of caffeine (>500 mg per day) are generally discouraged by health authorities.
Note:
• The Australian Institute of Sport educates athletes about caffeine, including the potential situations of performance enhancement, the benefits of using low doses of caffeine to achieve these effects and the risks of side effects
• The AIS does not do research on caffeine
• The AIS does not stock concentrated forms of caffeine, and does not provide caffeine to athletes for performance enhancement
Further Reading
Burke LM. Caffeine and sports performance. Appl Physiol Nutr Metab. 2008; 33: 1319-34
Please refer to summary table on research conducted on caffeine and sports performance.
