Review: Caffeine Supplementation

Kyle Shireman – Lock Haven University

Caffeine supplementation has come to be a major issue in the sports and exercise world. It is a socially accepted drug, and the supplementation of caffeine has become of concern within the last decade. Traditionally caffeine supplements were directed only towards endurance athletes, but have become popular in other aspects of training as well. Caffeine is considered a stimulant and will stimulate a person’s central nervous system (Smith 2010, Goldstein 2010). When consumed caffeine will be completely absorbed in the stomach and small intestine (Astrino 2010). After absorption the caffeine will be metabolized within the liver. Caffeine itself is a trimethylxanthine amino acid. In the liver enzymes will break down the trimethylxanthine amino acid into a simpler dimethylxanthine amino acid and other various amino acids as well (Davis 2009). Caffeine has been shown to affect various tissues within the human body. It has been used since the Stone Age to enhance muscular work (Davis 2009, Astrino 2010). It occurs naturally and can be found in a lot of our daily intake diets. Naturally occurring caffeine is found in leaves, nuts, fruits and seeds (Burke 2007, Astrino 2010). This caffeine is later processed and put into our sodas and various teas. It has been found that 90% of adult consume caffeine in their diets on a daily basis (Astrino 2010, Burke 2008)

Caffeine can be found in a lot of our foods and drinks that are found within our daily diets. Caffeine occurs naturally in leaves, nuts, fruits, and seeds. The accessibility of majority of the products that contain caffeine has increased the intake (Davis 2009). Caffeine is commonly found in many different drink products. More commonly it will be found in sodas and teas. However recently more and more energy drinks have started to add caffeine into their recipes for athletes to ingest (Davis 2009). Coffee however is known to be loaded with caffeine. Some studies have shown that consuming caffeine in the form of coffee has increased an individual’s visual processing time with computer or pen and paper tests (Foskett 2009). However, too high of a coffee consumption may have negative effects. Studies have shown that too high of a coffee intake will actually negate any stimulus response, giving you that crash feeling (Burke 2007). Caffeine is also found in foods that we consume on a regular basis as well. The most common consumption of caffeine can be found within chocolate. Caffeine can be found within the cocoa powder used to make the chocolate, from the cocoa bean (Astrino 2010, Wu 2010). However, caffeine is not only found in food and drinks, it is also used for a number of prescription and over the counter medications. The used of medicinal caffeine has an intention of headache and pain relief (Astrino 2010). Caffeine is the world’s most commonly used drug and this can be attributed to our daily intake of the previously stated products as well as various others as well (Astrino 2010).

Consumption of caffeine may however have some side effects. World health organizations’ discourage the intake of large amounts of caffeine. They consider an intake of 7500 mg of caffeine in one day an overdose (Burke 2008). Caffeine consumption can also lead to anxiety, restlessness and headaches (Astrino 2010). There is no set amount of consumption that will lead to these side effects. It is instead each individual person’s tolerance of caffeine that will determine if they are at risk of the side effects of caffeine consumption. Because caffeine is a diuretic, it can also cause frequent urination and may lead to dehydration (Burke 2007). Side effects are not typically seen with the consumption of caffeine however with a low tolerance or an increased intake could prove havoc on the body.

Although caffeine is not a fully banned substance, it is the world’s most widely used drug. This statement has driven the United States Food and Drug Association (FDA) to make recommendations for the consumption of alcohol. The FDA considers the intake of 200 mg per day as the average intake for and adult. This is equivalent to 2 five ounce cups of coffee or 4 sodas. The FDA does however regulate the amount of caffeine that can go into the products in which we consume on a daily basis. For example, the FDA regulate the insertion of caffeine in colas to be 0.02% or 200 parts per million. Another recommendation they have is directed towards those individuals that have heart problems. They should not ingest large amounts of caffeine because the caffeine will make the heart work harder, and could cause complications. Caffeine is also not recommended for individuals who suffer from anxiety or panic attack issues. This is because caffeine is a stimulant and has the ability to make people feel on edge and jittery, in turn this may exacerbate their problems and make these individuals feel worse. In the sports world some supplements that contain caffeine have been banned in sport. The FDA has banned the use of Ephedra, Yellow Jackets, and Black Beauties from sport. Some of these products have been shown to cause death in athletes. The FDA website shared information regarding the tragic death of a 16 year old football player after he ingested the product yellow jackets. This death was the one that made the FDA go onto full alert and led to the banning of the substances, because of their “street-drug” designation. Though the FDA has banned these substances, the intake of caffeine is not banned within any sport sanction.

Though the FDA does not have any regulations for caffeine supplements in sport, other organizations do have sanctions for caffeine levels in athletes. The National Collegiate Athletic Association (NCAA) has banned caffeine supplementation. However, because caffeine is part of the average person’s daily diet, they allow lead way in urinary levels for traces of caffeine. When performing urinary drug tests, NCAA athletes have to have a caffeine level of 15 micrograms per milliliter. This may seem minor, but it is the level of normal daily dietary intake (Davis 2009). The reason the NCAA has banned the use of caffeine to a certain extent is because of the use of the supplement as a stimulant in sport. The NCAA however is not the only organization to ban the use of caffeine supplements. The World Anti-Doping Agency (WADA) originally banned the use of caffeine altogether in 2004. On the contrary, the 2004 banning of caffeine however went through a lot of scrutiny and was later revoked. The WADA decided that instead of a total ban, athletes would be able to have caffeine levels to a certain extent. The agency then implemented restrictions allowing only normal dietary levels of caffeine to be found in drug tests. The recommended normal dietary intake is 7 mg or less per body weight (Burke 2008). The last organization to place restrictions on the use of caffeine supplementation was the International Olympic committee (IOC). The committee reserves the right to measure athlete’s drug levels within their urine. The cutoff for passing the IOC drug testing procedures is 12 micrograms/milliliter of caffeine within the urine (Ping 2010, Burke 2008). I feel that the use of caffeine supplements as a stimulant should be banned. The use of any supplements for that matter towards improving performance should be considered cheating. However, I do feel that these organizations did the right thing at allowing some caffeine within the athlete’s systems. It would be extremely hard for athletes to cut caffeine out of their diets totally.

Caffeine supplementation has been studied throughout many forms of research to determine the purpose of the caffeine intake. Throughout the common population it is a consensus that caffeine is used to reduce fatigue. Caffeine is considered to be an adenosine receptor antagonist (Davis 2009, Burke 2008, Goldstein 2010). Adenosine stimulates the release of dopamine in the brain. As an adenosine antagonist, caffeine replaces the adenosine and fills the receptors, in turn blocking the release of dopamine. Dopamine is a neurotransmitter that gives a person the sense of feeling tired. However, by blocking the release of dopamine, caffeine alters the perception of feeling tired and reduces the sense of fatigue (Davis 2009, Goldstein 2010, Burke 2008). Caffeine in some studies has also shown to effect fat utilization. When ingested caffeine promotes the utilization of fat as a fuel for the body, in turn sparing the muscle glycogen store (Burke 2008, Smith 2010, Goldstein 2010). The main purpose caffeine supplementation is used in sport is to enhance performance and endurance. Those exercises particularly targeted for use of caffeine supplementation are prolonged, intermittent, and exhaustive activity (Wu 2010). Caffeine has also been shown to enhance levels of performance as well. Research suggests that the ingestion of caffeine motor unit recruitment during maximal voluntary contraction within the muscle leading to a strength increase. This strength increase could then lead to an increased performance based on the type of competition the athlete is competing in (Jaworski 2010). However, the amount of caffeine intake does have some scrutiny. Tests have shown that ingesting small to moderate doses of approximately 1-3 mg/kg body mass has shown to be just as efficient as the intake of large doses of 5-6 mg/kg of body mass to enhance prolonged performance (Burke 2008). Other research has shown that caffeine intake can decrease muscle pain from eccentric resistance training. The caffeine supplementation has also shown to decrease the delayed onset of muscle soreness (DOMS) (Wu 2010). The purpose of caffeine supplementation has taken a lot of forms; however, the greatest purpose still tends to be for pain relief.

Caffeine is known to provide increased performance with supplementation. However it has also been shown to only be beneficial to certain athletes. The intake of caffeine has proven to have effect on decreasing pain in individuals, from both a medicinal standpoint and for decreasing aspects of training such as DOMS (Wu 2010, Davis 2009). In the training and competition realm, caffeine supplementation has become a touchy subject with regards to athletes ingesting the supplement. The main goal in which athletes wish to accomplish with ingesting caffeine is to provide some form of ergogenic aid (Burke, 2008). This in turn has the ultimate goal of increasing the athlete’s performance in some way. Those athletes who are more likely to consume caffeine supplements are speed and endurance athletes (Burke 2007). In a survey of athletes who competed in the Triathlon World Championships in 2005, 89% of those athletes were found to have used some form of caffeine supplementation (Ping, 2010). In one instance researchers hypothesized the idea of acute supplementation of caffeine with regards to cardiovascular responses in hot and humid climates. Through this study researchers took 9 Malaysian recreational runners and placed them into a hot and humid climate. Within this climate the subjects were asked to run on a treadmill for 4 minutes each at 4 different speeds. Researchers then based their findings off of oxygen uptake at submaximal running speeds. The findings of this study show that the runner’s endurance had increased with those who were found to be non-caffeine users (Ping, 2010). This study was one of many different studies in which I found all pointed to some increase in endurance performance with caffeine supplementation.

Since majority of the research already states that caffeine has some kind of effect on endurance athletes, I decided to take my research into other aspects of training. Anaerobic exercise benefits have been recently questioned with regards to caffeine supplementation. In one research article examiners tested caffeine supplementation along with various other components such as creating and various amino acids. The components were mixed together in a pre-exercise supplement that the 24 moderately-trained males drank. The testing procedure for this research was through a Wingate test. The Wingate test is designed to examine peak anaerobic power, anaerobic fatigue and total anaerobic capacity. Subjects were tested over a 3 week high-intensity interval training bout. Following testing procedures the results of this study pointed towards no improvement in anaerobic exercise. However, research articles used by this research team had shown that caffeine alone with a 5-6 mg/kg of caffeine intake provided an increase with high-intensity short duration exercises. This may be because of the cardiovascular response and training volume (Smith, 2010). In another literature review, researchers found that again caffeine supplementations did provide an ergogenic effect in individuals. This study found that individuals ingesting caffeine supplements increased performance, and an increase in maximal anaerobic power by 7% in both trained and untrained individuals (Davis, 2009). Going along with the anaerobic theme two articles also found an increased effect with caffeine supplement intake. In one test researchers questioned the efficacy of caffeine supplements with upper body strength in resistance trained women. This study consisted of testing 15 resistance trained women performing 2 exercise trials. The trials consisted of finding each individual’s one rep max and repetitions to failure. Following testing of the individuals, the researchers found that the ingestion of 6 mg/kg caffeine 1 hour prior to testing had an increase performance with regards to resistive exercise (Goldstein, 2010). Other studies examined the effects of caffeine ingestion on growth hormone response to a single bout of resistance exercise. This study found that the ingestion of a caffeine supplement 1 hour prior to resistive exercise increased the growth hormone levels in the tested individuals (Wu, 2010). With majority of the research pointing toward increase endurance affects, I feel that caffeine could also have anaerobic effects as well.

Aside from the aerobic and anaerobic studies, one study examined the effects of caffeine supplementation on cognitive function. This study was conducted with the assistance of 12 male soccer players. Testing for this study consisted of the players performing a minimum of 5 attempts of the Loughborough Soccer Passing Test (LSPT). After the 12 athletes completed the minimum of 5 attempts at the LSPT, researchers tabulated and analyzed the results. Through examining of the results the researchers found that ingestion of a gelatin capsule consisting of 6 mg/kg of caffeine had improved implications on cognitive function. The individuals increased in passing accuracy through visual perception with the supplementation of caffeine (Foskett, 2009). This study was interesting to me because it took the effects of caffeine out of the box and examined an effect that not many other researchers took into account. However, caffeine intake at an increased level can potentially cause an increase in heart rate which in turn impairs fine motor control (Burke 2007). This factor could have a negative effect on the cognitive functions of individuals who take caffeine supplements.

Throughout my research I found conflicting findings with regards to the supplementation of caffeine. However, one thing is for sure, with majority if not all of the articles found suggesting that caffeine has an increased effect on endurance athletes, I feel that it will have some kind of effect as well. From a standpoint of banning the use of caffeine, I feel that organizations are doing a great job with keeping restrictions on the amount accepted. There is no way that an individual could cut caffeine out of their diet totally, and this leads me to agree that a maximum amount in urine is a great method for measuring the appropriate levels of caffeine. Caffeine supplementation is a unique form of ergogenic aid. It has confirmed results showing that it can increase both aerobic and anaerobic exercise. However the dangers of an increased intake make me question the efficacy of caffeine. Though majority of the side effects are insignificant, caffeine has the tendency to cause over arousal. This over arousal may have the ability to affect sleep patterns which in turn will decrease performance (Burke 2007).


1.Astrino, T.A., Roberson, D.W. (2010). Efficacy of Acute Caffeine Ingestion for Short-Term High-Intensity Exercise Performance: A Systematic Review. Journal of Strength and Conditioning Research, 24(1), 257-265

2.Burke, L.M. (2007) Practical Sports Nutrition. Champaign, IL: Human Kinetics

3.Burke, L.M. (2008). Caffeine and Sports Performance. Applied Physiology, Nutrition, and Metabolism, 33, 1319-1334.

4.Davis, J.K., Green, J.M. (2009). Caffeine and Anaerobic Performance: Ergogenic Value and Mechanisms of Action. Sports Medicine, 39 (10), 815-832.

5.Food and Drug Association. (2007). Medicines in My Home Caffeine and Your Body. Retrieved November 4, 2010. From

6.Foskett, A., Ali, A., & Gant, N. (2009). Caffeine Enhances Cognitive function and Skill Performance During Simulated Soccer Activity. International Journal of Sports Nutrition and Exercise Metabolism, 19, 410-423.

7.Goldstein, E., Jacobs, P.L., Whitehurst, M., Penhollow, T., & Antonio, J. (2010). Caffeine Enhances Upper Body Strength in Resistance-Trained Women. Journal of the International Society of Sports Nutrition, 7 (18), 1-6

8.Jaworski, C.A. (2010). Latest Clinical Research Published by ACSM. Current Sports Medicine Reports, 904, 190

9.Ping, W.C., Keong, C.C., & Bandyopadhyay, A. (2010). Effects of Acute Supplementation of Caffeine on Cardiorespiratory Responses During Endurance Running in Hot & Humid Climate. Indian Journal of Medical Research, 132, 36-41

10.Smith, A.E., Fukuda, D.H., Kendell, K.L., & Stout, J.R. (2010). The Effects of a Pre-Workout Supplement Containing Caffeine, Creatine, and Amino Acids During Three Weeks of High-Intensity Exercise in Aerobic and Anaerobic Performance. Journal of the International Society of Sports Nutrition, 7 (10), 1-11.

11.Wu, B.H., Lin, J.C. (2010). Caffeine Attenuates Acute Growth Hormone Response to a Single Bout of Resistance Exercise. Journal of Sports Science and Medicine, 9, 262-269

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