Jan 29, 2015
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Whether it’s consumed to enhance performance or as part of the daily diet, caffeine can be a negative for today’s competitive athlete.

By Laura Smith

Laura Smith is an Assistant Editor at Training & Conditioning.

It’s a psychoactive drug affecting several powerful neurotransmitters. When consumed, it triggers changes in the same area of the brain activated by nicotine, cocaine, and heroin. Used regularly, it leads to tolerance and addiction. Attempting to discontinue use prompts painful withdrawal. As many as nine out of 10 of your athletes may be using it, and in fact, you probably had a dose of it today yourself.

Caffeine. Eighty to 90 percent of American adults consume it every day, and student-athletes on college campuses are no exception. Increasingly, high schoolers are rivaling adults in their caffeine use, downing sodas and visiting coffee shops for frozen or sweetened caffeinated drinks. In addition, many student-athletes turn to the drug to enhance their athletic performance.

Certainly, concern about caffeine use pales in comparison to the use of substances like steroids and ephedra. But heavy consumption can have some very real downsides for student-athletes’ health and performance. And while there is laboratory evidence that caffeine enhances performance, athletes who use it as an ergogenic aid need to be educated about the risks and realities of competing under its influence.


Structurally, caffeine mimics one of the body’s natural chemicals, a neuromodulator called adenosine. Under normal circumstances, adenosine acts as the “brakes” in the central nervous system, inhibiting neuronal firing and neurotransmitter release. As adenosine concentration builds slowly in the body over the course of the day, its “slow down” effect leads to feelings of sleepiness and, eventually, to sleep.

When caffeine is ingested, because it is similar to adenosine, it binds to adenosine receptors and “plugs them up,” according to Laura Juliano, PhD, caffeine researcher and Assistant Professor of Psychology at American University. “With caffeine blocking adenosine receptors, adenosine cannot have its normal effect, so you feel less fatigued and more alert,” she says.

Caffeine also increases the availability of many neurotransmitters, which can affect the body in several different ways. “Caffeine doesn’t target one neurotransmitter—it targets adenosine, and through its effect on adenosine, it affects everything else,” Juliano says. With the flood of neurotransmitters and the short-circuiting of fatigue-producing adenosine, it makes sense that most people feel more energized and better able to focus with caffeine, whether they’re recalling answers for a physics exam or completing a tough practice.

Why is caffeine so addictive? Researchers recently uncovered at least part of the answer when they discovered that caffeine releases dopamine (the “pleasure and reward” neurotransmitter) in the part of the brain called the nucleus accumbens—an area that plays an important role in all addictive drugs. Researchers believe this may explain why casual caffeine users often become dedicated, and then addicted, users.


When student-athletes become daily caffeine users, particularly with heavy use, both their health and performance may suffer in ways they aren’t even aware are happening. One of the biggest risks: Caffeinerisks is that caffeine use disrupts sleep, and student-athletes are often sleep-deprived to begin with.

“High school and college students are notorious for not getting enough sleep, and especially when they are athletes, it’s absolutely essential that they get enough rest to repair muscle tissue and perform optimally,” Juliano says. “Caffeine increases the length of time it takes to fall asleep and decreases total sleep time.”

It doesn’t require downing a grande coffee right before bed to see the effect, either. Studies have shown that using consuming a moderate amount of caffeine early in the day can reduce the quality and quantity of that night’s sleep.

Another concern involves caffeine’s ability to produce anxiety. Again, the effect does not require huge doses. Starbucks reports that its 16-ounce coffee contains 400 milligrams of caffeine—the exact amount researchers administer in the laboratory to induce anxiety, according to Juliano. “There is already a lot of anxiety in the lives of most student-athletes,” she says. “And caffeine is going to magnify it.”

A student-athlete who has an exam looming, a paper due, and a game coming up may down a mug or two of coffee to make it through the day, then attribute feelings of stress and anxiety to the workload. “In reality, caffeine is probably making them feel much worse, but they don’t realize it,” says Juliano.

Daily consumption of coffee and colas also deprives the body of calcium, according to Barbara Lewin, RD, LD, who sees professional and student-athletes at a Fort Myers, Fla.-based private practice. “Coffee and colas are high in phosphorus, and the body requires a certain phosphorus-to-calcium ratio,” Lewin says. “If your phosphorus intake is high, and you don’t ingest enough calcium, your body will pull calcium from your bones. Most student-athletes don’t get enough calcium in their diets as it is. Often, when I look at a student-athlete’s daily calcium intake alongside their use of coffee and colas, they are in a negative calcium balance.”

There are two other nutrition negatives to be aware of. First, since caffeine increases the production of stomach acid, large amounts can induce an upset stomach or acid reflux. Second, while caffeine is no longer believed to be a diuretic, most caffeinated beverages are not particularly good sources of hydration. If they replace water or sports drinks in an athlete’s diet, chances of dehydration increase. (See “Does Caffeine Dehydrate?”.)

Last but not least, student-athletes who use caffeine daily will build up a tolerance, gradually needing more and more to achieve the same effect. They’ll also develop dependence and feel like they need caffeine to function normally. “When it comes to chronic caffeine users, it’s often difficult to separate the effect of the drug from the effect of not having the drug,” Juliano says. “In other words, they may think caffeine makes them feel and perform better, but in reality, it just keeps them from feeling bad from not having it.”

Few sports nutritionists advise college athletes to avoid caffeine altogether. It’s simply too pervasive an ingredient in many foods and drinks. But how much is too much?

“If a student-athlete does not want to be physically addicted to caffeine, he or she needs to use well below 100 milligrams a day, which means drinking only one caffeinated soft drink or a very small cup of coffee a day,” Juliano says.

For student-athletes who find that recommendation unrealistic, nutritionists advise that they keep their daily intake under 300 to 400 milligrams a day. While this amount does cause dependence on the substance, other side effects, such as anxiety, sleeplessness, and digestive disturbance, generally don’t occur. Staying under 400 milligrams requires limiting intake to about two cups of coffee or three caffeinated soft drinks a day.


Beyond consuming coffee as part of their daily routines, many athletes are turning to caffeine as an ergogenic aid. “The prevalence of caffeine as a performance aid is something I’m seeing more and more,” says Josh Hingst, MS, RD, CSCS, USAW, Assistant Strength and Conditioning Coach and Sports Nutritionist at Florida State University.

“I don’t see student-athletes taking caffeine pills, but I do see them drinking more caffeinated beverages, especially the so-called energy drinks, before games or meets,” agrees Leah Moore Thomas, MS, RD, LD, Sports Nutritionist at Georgia Tech. “And I’ve had more athletes ask, ‘If I drink coffee before my swim meet or my race, is it going to help me?'”

The answer, according to a solid body of literature, is probably yes—but with some big caveats. Caffeine may boost performance, depending on the student-athlete’s sport and his or her individual response to the substance. Particularly with endurance exercise, multiple studies have shown that athletes given caffeine prior to workouts in the laboratory outperform those given a placebo.

“There is a wealth of information to suggest that caffeine allows people to exercise harder and longer in aerobic events lasting 20 minutes or more,” says Lawrence Spriet, PhD, an exercise physiologist, caffeine researcher, and Professor at Canada’s University of Guelph. “Caffeine holds up as a solid performance enhancer in endurance events.”

The support for performance improvement in shorter-duration events is less definitive, but growing. “Recent studies provide increasing evidence that caffeine can also improve performance during sprinting events lasting 90 seconds or more,” Spriet says. “There are few studies looking at throwing events, power events, or sprints lasting 90 seconds or less, and most researchers agree it’s unlikely that caffeine produces any true physiologic effects in these events. But even there, an improved sense of alertness and awareness caused by caffeine could translate to improved performance.”

Until recently, physiologists believed that caffeine aided performance by allowing the body to tap into fatty acid stores more quickly, thus sparing muscle glycogen to be used later in the event as the body fatigues. However, that theory has not held up in newer research. Researchers now believe the majority of caffeine’s performance effect results from simple central nervous system stimulation.

“As the athlete gets tired, he or she is better able to maintain focus and level of effort with caffeine,” Spriet says. “Caffeine also reduces perceived exertion, so athletes report that they don’t feel like they are working as hard.” In laboratory studies, caffeine’s CNS stimulant effect also seems to boost awareness, vigilance, and alertness, particularly during boring, long-term exercise bouts.

However, the real question mark comes when one attempts to translate laboratory findings to real life competition. Research studies typically put athletes through very specific physical challenges with few variables, like treadmill running or stationary cycling. “Clearly the translation from that to running a 1500-meter race is quite easy,” Spriet says. “But with sports like soccer, ice hockey, and basketball, the translation is very complicated. When you introduce all the variables that are involved with team sports, it becomes much harder to measure whether caffeine has improved an individual athlete’s performance.”

However, even with these caveats, it’s likely that many athletes will see some performance improvement with caffeine. “The majority of the lab studies and the few field studies that have been done suggest very strongly that caffeine does boost performance,” Spriet says. “If you were a betting person and you were looking for something legal you could take that was likely to give you a performance benefit, caffeine would be at the top of the list.”


If caffeine can possibly boost performance, should athletic trainers advocate student-athletes using it? When it comes to high school student-athletes, Spriet has an unequivocal answer: absolutely not.

“I do not recommend caffeine use with developing individuals,” he says. “In fact, if it was up to me, it would be banned for athletes under 18.”

Juliano agrees. “For one thing, from a chemical standpoint, we don’t know whether caffeine affects a developing central nervous system differently from an adult central nervous system, because that research cannot be done for ethical reasons,” she says. “We know that the brain is still developing, and that caffeine affects brain neurotransmitters, but beyond that, we just don’t know.”

In addition, advocating that high school athletes use caffeine to perform better may put them at increased risk for trying other, and more dangerous, ergogenic aids. “Telling a 14- or 15-year-old athlete that caffeine supplementation is an okay idea sends a dangerous message,” says Lewin. “It opens them up to the idea of a quick fix, of taking a pill to become a better athlete. Can it lead to abuse of other performance enhancers? We don’t know for sure, but it’s certainly an issue to be aware of.”

The fact is, however, high school student-athletes are getting the message that caffeine will help them play better from other sources, so it falls to athletic trainers to offset that message with education. “We know that children and adolescents are using more caffeine than ever before,” Juliano says. “They are a huge share of the market for soda and energy drinks. For athletic trainers working with adolescents, it’s critical to educate them that caffeine is a drug, that it causes physical dependence, and that there are much better ways to achieve more on the court or field.”

It’s also important to be aware of the messages high school athletes are getting from their coaches regarding caffeine. “Ask the coaches you work with how they feel about caffeine use,” Juliano says. “Are they neutral, or are they encouraging or discouraging its use? And take that opportunity to educate coaches about the issue, because they are the ones most likely to notice if athletes are using caffeine to enhance performance, and their messages go a long way.”


With older student-athletes, a message that combines information about caffeine’s risks with education about using it safely may be a more realistic approach. “Once athletes are in college, many of them are going to use it as an ergogenic aid whether athletic trainers advocate it or not,” Spriet says. “So athletic trainers need to be there to say, ‘If you are going to use it, here are some guidelines so you don’t harm your body.'”

Hingst agrees. “I think the message from college athletic trainers needs to be, ‘There are a lot more important things to consider when you’re trying to improve your performance, like nutrition, hydration, training, and rest. But if you are going to use caffeine in an attempt to boost your performance, here is how to do it safely,'” he says.

Education on the safe use of caffeine as an ergogenic aid needs to include the following factors:

Dose: Research indicates that doses of three to five milligrams per kilogram of body weight will provide a performance effect without health risks. “For a 70-kilogram (154-pound) athlete, three milligrams per kilogram is only 210 milligrams of caffeine,” Spriet says. “You can easily get that from two cups of coffee.”

Athletes who ingest too much caffeine before an event are more likely to see a performance detriment than a benefit, from caffeine-induced headaches, anxiety, stomachaches, and focusing problems. They may also approach the caffeine limits set by the NCAA, which require athletes to have less than 15 micrograms per milliliter of urine. (The average 175-pound athlete would have to drink seven to 10 cups of coffee one hour prior to a test to exceed the NCAA limit, according to Spriet.)

Source: Spriet advises against using energy drinks, since they typically contain many other ingredients not regulated by the FDA. He believes the safest source is simply coffee. “For an adult athlete, one to three cups of coffee before an event, depending on the athlete’s weight, is very safe and is likely to provide them with a performance benefit, without adding sugar or other ingredients,” he says.

Timing: In general, caffeine should be consumed a half-hour to an hour before the start of the event. “The blood level of caffeine is maximized one hour after it’s taken, but effects start to show up by 30 minutes,” Spriet says. For events lasting longer than an hour, caffeine can be ingested right before the event.

Tolerance: Athletes who use caffeine as part of their daily diet are less likely to see a performance benefit from using it prior to exercise. “To avoid building up a tolerance, an athlete needs to abstain from caffeine for a few days prior to taking it before their event,” Lewin says.

Testing: “Advise athletes to try it during practices or workouts before using it during a game or meet,” Hingst says. “They need to have some experience using it first to see how they respond.”

Mixing It: Perhaps most importantly, advise student-athletes to be very aware of the ingredients in any other supplements they are taking. Combining caffeine and other stimulants often found in dietary supplements can be a deadly mistake.

“Both ephedrine and ephedra, in and of themselves, can decrease fibrillatory potential and put an athlete at higher risk for a sudden arrhythmic death,” says Richard Stein, MD, Cardiologist at Beth Israel Hospital in New York City and a national spokesperson for the American Heart Association. “Adding the tachycardic influence of caffeine could certainly make that worse and would definitely increase the risk.” While ephedra is banned from sale in the United States, athletes are still able to obtain it on the black market. Ephedrine is readily available in many cold remedies and “fat burning” supplements.


Even with new research on caffeine and performance available, nutritionists still recommend downplaying its role to athletes. “When athletes ask me about boosting performance with caffeine, I ask them, ‘What have you done to improve your breakfast, lunch, dinner, and recovery meals? How is your hydration, training, and rest?'” Lewin says. “Depending on their sport, their individual response, and a host of other variables, caffeine may give them a slight boost. But it is not going to make up for not having these foundational pieces in place.”

“Athletes need to be reminded that there is a difference between feeling really energized and actually being energized,” Stein adds. “Actually being energized is dependent on attention to proper fueling, hydration, and training, and those are the things that we need to be emphasizing.”


For student-athletes who need to lower their caffeine intake, it’s essential to help them develop a strategy, because withdrawal symptoms can hit harder than they expect.

Caffeine researcher and Assistant Professor of Psychology at American University Laura Juliano, PhD, and her colleague Roland Griffiths recently conducted a review of existing literature on caffeine withdrawal. “One of our most important conclusions was that caffeine withdrawal is clinically significant,” she says. “Some people become so ill that they mistake the withdrawal for the flu. It’s important to take caffeine withdrawal seriously.”

The most pronounced symptom is usually a pounding headache, and caffeine’s affect on adenosine is to blame. “Adenosine is a vascular dilator in the cerebral system,” Juliano explains. “Caffeine is a vasoconstrictor, so when it’s used regularly, it fights adenosine to constrict blood flow in the brain. The body fights back to keep veins open. During withdrawal, the body is still pushing those veins open, but there is no caffeine there to fight against. At that point, the veins blow open, causing a pulsating headache that is sensitive to movement. The headaches can last anywhere from one to three weeks and can be more pronounced during physical activity.”

An often-unanticipated symptom of caffeine withdrawal is mood disturbance. Since caffeine works to make several of the brain’s “feel good” neurotransmitters more available, suddenly eliminating it can cause irritability, difficulty concentrating, and depression. Fatigue is another common symptom of caffeine withdrawal, since the central nervous system must adjust to no longer receiving a regular chemical stimulant.

Juliano suggests helping student-athletes cut back by letting them know what to expect. “Explain to the student-athlete that whenever you use a drug regularly, your body makes a series of adjustments,” she says. “When your body doesn’t get the drug, it is forced to go through a period of readjustment—and that can significantly interfere with performance in school and athletics. Help them choose an appropriate time to cut back. Right before final exams or an important game is probably not the best time.”

Leah Moore Thomas, MS, RD, LD, Sports Nutritionist at Georgia Tech, advises student-athletes to reduce caffeine gradually. She first has the athlete tally up all the sources of caffeine they typically use, especially hidden ones like coffee-flavored yogurt, or caffeine-containing medications.

“Then I ask them to reduce it a little at a time,” she says. “If caffeine is present at three meals a day, I have them replace it at one meal with juice or water or a decaffeinated soda or coffee. Once they do that for a while, I ask them to try including caffeine only once a day, and then go to every other day. My goal is for our student-athletes to reach a level of use where if they don’t have caffeine for a day, they don’t feel any adverse effects.”


For many years, the idea of “caffeine as a diuretic” was common wisdom. But recent research suggests that, at least in this respect, caffeine has been getting a bad rap. Lawrence Armstrong, PhD, FACSM, Professor at the University of Connecticut’s Human Performance Laboratory, published a study in 2002 debunking the dehydration myth.

“We took 59 healthy college males and studied them during 11 days of controlled caffeine intake,” Armstrong says. “One group took no caffeine, a second took three milligrams per kilogram of body mass, and a third took six milligrams per kilogram of body mass. We evaluated them on 20 hydration indices, and the results across all three groups were virtually identical.

“The amount of water retained by the body from a caffeinated beverage is virtually identical to the amount retained from a non-caffeinated beverage,” Armstrong continues. “There is no evidence that caffeine dehydrates the body.”

Other studies have found similar results, prompting researchers to conclude that any increases in urine output after consuming caffeine are not a result of the caffeine, but of the water typically ingested along with it.

Sports nutritionists, however, are quick to point out that caffeinated beverages still should not be the hydration source of choice for athletes. “Dehydration is such a huge issue for student-athletes,” says Leah Moore Thomas, MS, RD, LD, Sports Nutritionist at Georgia Tech, “that the message still needs to be, ‘Caffeine itself may not dehydrate you, but colas and energy drinks are also not designed to properly hydrate you, and they should not be your major source of fluids.'”

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