Caffeine as an Ergogenic Aid

Can You Use Caffeine as an Ergogenic Aid – Is Caffeine a Diuretic

Caffeine is a naturally occurring chemical found in certain plants including cocoa beans, kola nuts, yerba maté, guarana, and the world’s most beloved tea leaves & coffee beans. But, health-conscious people need to question is caffeine a diuretic substance before using it excessively. Coffee & tea have become the major sources of caffeine intake, and many consider it as an essential dietary component to get them through the day.  It is not uncommon for people to drink between 3-6 cups of tea or coffee per day, as they find it helps them to feel better, have more energy and be able to carry out daily tasks more effectively. A cup of strong coffee or a caffeine supplement before training is also common practice for athletes and gym users to improve mental and physical performance.

On the other hand, it is a common belief that drinking caffeinated beverages like tea and coffee can lead to dehydration. Hydration is obviously important for health and exercise performance, but the question is, should caffeine intake be reduced or avoided to maintain fluid balance, and does it actually improve performance?

Using Caffeine as an Ergogenic Aid

Caffeine is well researched as a nutritional strategy to enhance performance. To say that caffeine improves exercise performance is a simple answer to a complex question as there are many factors to consider. Caffeine can help you achieve your athletic goals. Without going into too much detail, I will outline the basic findings that support caffeine as an ergogenic aid in different sports.

Caffeine and Endurance Exercise ( 60 minutes or longer )

  • There is extensive evidence to suggest that caffeine ingestion improves endurance performance.
  • More is not necessarily better, with 3-6g/kg body mass showing to be most effective (see Figure 2).
  • Taking caffeine 30-45 mins before the event, during the event and in the late stages when fatigue starts to occur are all effective strategies, but recommendations are specific to the event, the athlete, and the practicalities of caffeine intake.
  • Training low (fasted – before breakfast or glycogen depleted) performance may be rescued by caffeine ingestion, thus increasing training adaptations.
  • Endurance performance is improved by delaying the onset of fatigue, which may be due to an increased fat utilisation and sparing of muscle carbohydrate (glycogen) stores, however, this remains elusive. Complement caffeine with recovery foods after exercise to replenish muscle glycogen.

Caffeine for Athletes in High-Intensity Sports ( 1- 30 minutes )

  • Caffeine ingestion 45-60 minutes prior to high-intensity sports events may improve performance.
  • A lot of the research to support this has used doses of 6mg/kg body mass, however, 3mg/kg may be equally as effective.
  • Performance enhancement may be subject to caffeine’s stimulatory effects on the central nervous system, reducing feelings of perceived exertion and pain, increasing reaction time, alertness and mood, ultimately delaying fatigue.

Caffeine for Intermittent ‘stop and go’ sports (60-90 mins or longer)

  • Individual and team-based sports including tennis, football, rugby, hockey, cricket, etc, have all shown improvements in performance following caffeine ingestion.
  • 3mg/kg body mass appears to induce similar positive effects compared to 6mg/kg.
  • Total distance covered, repeated high-intensity bouts (e.g. sprints, jumps, scrums, tennis serves), skill, accuracy and cognition are all areas of performance that may be attributed to caffeine ingestion.

Caffeine as an Ergogenic Aid in Skill Sports

  • Sports that rely heavily on skill and accuracy e.g. golf, shooting, archery, table tennis, which do not involve fatiguing exercise per se, but are conducted over long periods that likely cause feelings of mental and physical fatigue.
  • Low-moderate doses of caffeine (1-2mg/kg) consumed both before and during an event may offer the most beneficial effects, rather than high doses which may cause symptoms of jitters and anxiety.
  • May improve golf putting & drive distance performance, archery target accuracy, overall mood and perceived feelings of energy and fatigue.

Relation of Caffeine and Athletic Performance in Strength and Power Sports (<20 seconds)

  • Maximal efforts lasting just seconds include weight lifting, sprints, jumps and throws; common single activities for track and field athletics, sprint cyclists and also powerlifters.
  • The influence of caffeine for maximal strength (1 rep max) training appears to have minimal effect, however, it’s more likely to enhance muscular endurance – increased reps to failure.
  • This also applies to repeated maximal bouts of sprinting, cycling, throws (discus, shot-put) or jumps (long, high jump).

Caffeine and exercise performance

Figure 2.  Exercise time to exhaustion. Data are mean data for exercise duration after placebo (0 mg/kg) or 3, 6, or 9mg/kg of caffeine. Letters a & b symbolise a significant difference from each other.

Is Caffeine a Diuretic? : Caffeine and Hydration

Tea and coffee are the most widely consumed drinks in the world, after water. Theoretically, caffeine may have a diuretic effect as it disrupts an important regulator of kidney function, renal water & electrolyte transport, which can stimulate urine output causing water & electrolyte loss (Rieg et al., 2005). This has led to the belief that regular caffeine intake results in dehydration and some studies have supported this theory. However, these studies report a range of caffeine forms and doses in populations who do or do not regularly consume caffeine-containing beverages. Together, these data suggest that high doses of caffeine (>500mg) can increase urine volume in caffeine-naïve (non-regular consumers) individuals, but low to moderate doses (<250mg) do not induce a diuretic effect.

Caffeine is well proven to improve athletic performance when taken in doses of 3-6mg/kg body mass 30-60 mins before training, however you can have too much caffeine and this may cause a diuretic effect in athletes who aren’t used to it. Abstaining from caffeine for just 4 days is sufficient for this tolerance to be lost (Fisher et al., 1986).

Does Coffee Dehydrate You?

There is one particular study in 2014 that strongly supports the hydration qualities of coffee when consumed in moderation by caffeine habituated males. Killer et al. showed that consuming 4 x 200ml coffee for 3 days to give a total of 4mg·kg·body weight of caffeine, did not influence total body weight, blood markers or 24h urine volume and markers, compared to the same quantities of water.

Caffeine content is not as high in tea as it is in coffee (see Figure 1), therefore a high as 9 cups per day is needed for a safe upper intake of 450mg caffeine. Scott et al. (2004) found no difference in hydration status between drinking tea or water when climbers were at altitude, where the risk of dehydration is extremely high. Six cups of black tea per day also have no negative effects on hydration when compared to water (Ruxton et al., 2011).

Consuming caffeine in doses of 3-6mg/kg body mass 30-60 mins before endurance sports like running, cycling and swimming has been shown to improve performance. But, people consuming coffee at a higher rate may experience caffeine’s diuretic effect in severity.

Therefore, regular consumption of tea & coffee (3-6 cups per day) contributes to total fluid intake and should not be seen as a diuretic. A higher intake of caffeine (>6mg·kg), however, may cause slight dehydration by increasing urine volume, so just have 1 tsp. of coffee in your drink!. When used in a proper amount, coffee is not dehydrating. But, when used excessively, coffee can cause dehydration.

Caffeine sources

Figure 1. The Caffeine content of drinks


Effects of Caffeine on Your Health

Every day it seems there’s a new link between something we always thought was good for us and a life-threatening condition…so what’s the score with caffeine?

Moderate intakes of caffeine consumed through beverages like tea and coffee do not appear to cause any adverse health effects in healthy people, and in fact may actually fight against the development of cardiovascular diseases and type 2 diabetes. Known side-effects include insomnia, digestive discomfort, increased heart rate and blood pressure, headaches, anxiety and restlessness, but this is due to large dosages and timings (insomnia by drinking before sleep).

However, there is one word in that sentence that determines people’s experiences with caffeine intake…moderate (moderation). Sadly people can, and have, died from caffeine overdoses, but this is rare. I actually heard of a case not so long ago, when Sports Science students were acting as subjects and were given a caffeine dosage in grams, instead of milligrams (Oops!). Luckily they survived.

On the brighter side, caffeine can offer many health benefits. Coffee and tea may also offer additional health benefits to caffeine alone, as they contain B-vitamins, phytochemicals and antioxidants, and moderate daily intakes (3-6 cups per day) can lower the risk of type 2 diabetes, cardiovasular disease, stroke and mortality.

Type 2 Diabetes

Van Dam et al. (2006) reported that 4 cups or more of coffee was better than just 1 cup per day for reducing the risk of type 2 diabetes in younger and middle-aged women. There were also no differences between caffeinated and decaffeinated coffee, but tea consumption did not influence type 2 diabetes risk.

Another study showed 3 cups of tea or coffee reduced the risk of type 2 diabetes by 42% in a prospective cohort of over 40,000 people (van Dieren et al., 2009).

Cardiovascular Disease

Moderate coffee consumption is inversely associated with the risk of heart failure, with the largest inverse association observed for consumption of 4 cups per day (Mostofsky et al., 2012). Likewise, coffee consumption does not increase the long-term risk of coronary heart disease and may even lower it in women (Wu et al., 2009).

High consumers of tea may have a lowered risk of CV disease than low/non-consumers (Fardet et al., 2014), and maybe attributed to tea’s flavonoid content and its impact on endothelial function, inflammation and cholesterol oxidation (Dwyer et al., 2013).

Tea consumption of 3 cups per day is also likely to reduce the incidence of stroke and mortality (Arab et al., 2013).

Cognitive function & dementia

Known for its short-term stimulatory effects on the brain, lifelong moderate consumption of caffeine/coffee may actually slow down physiological and age-related cognitive decline, and reduce the risk of Alzheimer’s disease. There have been mixed findings, with no definitive answer as to whether caffeine improves mental health later in life.

Drinking 3-5 cups per day during midlife may decrease the risk of dementia/Alzheimer’s disease by up to 65% (Eskelinen et al., 2009).

Middle-aged and elderly populations may be more sensitive to the protective effects of caffeine on declining cognitive function by improving reaction time, attention span and feelings of well-being (Swift et al., 1988; Rees et al., 1999).

Healthy Caffeine Intake

  • Caffeine is not a diuretic in low-moderate doses, meaning up to 6 cups of tea or coffee per day can contribute to your total fluid intake without causing dehydration.
  • This does not mean coffee/tea should replace water but together can keep you hydrated.
  • Regular caffeine consumption can develop a tolerance, therefore people who do not regularly drink tea or coffee may experience a slight diuretic effect.
  • Avoid consuming late at night as it can disrupt sleep quality
  • Caffeine tolerance can be lost after just 4 days of abstinence.
  • Regular caffeine/coffee/tea ingestion has many health benefits to fight against the development of cardiovascular diseases and type 2 diabetes, with some, but no conclusive evidence to suggest it improves cognitive health later in life.
  • Caffeine as a pre-training stimulant can improve endurance, high-intensity and intermittent sports performance, with just 3mg/kg body mass being sufficient to maximise performance.
  • 1-2mg/kg body mass may be sufficient to improve skill sports performance.
  • It may also improve repeated high-intensity bouts, but not necessarily maximal single (1RM) efforts.


Arab, L. et al. (2013). Tea consumption and cardiovascular disease risk. American Journal of Clinical Nutrition, 98, 1651S-1659S.

Dwyer, J. T. et al (2013). Tea and flavonoids: where we are, where to go next. American Journal of Clinical Nutrition, 98, 1611S-1618S.

European Food Safety Authority (2015). Scientific opinion on the safety of caffeine. ESFA Journal.

Eskelinen, M. H. et al. (2009). Midlife coffee and tea drinking and the risk of late-life dementia: a population-based CAIDE study. Journal of Alzheimer’s Disease, 16, 85-91.

Fardet, A. et al. (2014). Associations between food and beverage groups and major diet-related chronic diseases: an exhaustive review of pooled/meta-analyses and systematic reviews. Nutrition Reviews, 72, 741-762.

Fisher, S. M., et al. (1986). Influence of caffeine on exercise performance in habitual caffeine users. International Journal of Sports Medicine, 7, 276–280.

Maughan, R., & Griffin, J. (2003). Caffeine ingestion and fluid balance: a review. Journal of Human Nutrition and Dietetics, 16, 411-420.

Mostofsky, E. et al. (2012) Habitual coffee consumption and risk of heart failure: a dose-response meta-analysis. Circulation and Heart Failure, 5, 401-405.

Rees K. et al. (1999) The influences of age and caffeine on psychomotor and cognitive function. Psychopharmacology, 145, 181-188.

Rieg, T. et al. (2005). Requirement of intact adenosine A1 receptors for the diuretic and natriuretic action of the methylxanthines theophylline and caffeine. Journal of Pharmacology & Experimental Theraputics, 313, 403-409.

Ruxton, C. H. S. (2008). The impact of caffeine on mood, cognitive function, performance and hydration: a review of benefits and risks. Nutrition Bulletin, 33, 15-25.

Ruxton, C. H. S., & Hart, V. A. (2011). Black tea is not significantly different from water in the maintenance of normal hydration in human subjects: results from a randomised controlled trial. British Journal of Nutrition, 106, 588-595.

Scott, D. et al. (2004). The effect of drinking tea at high altitude on hydration status and mood. European Journal of Applied Physiology, 91, 493-498.

Swift C.G. & Tiplady B. (1988) The effects of age on the response to caffeine. Psychopharmacology, 94, 29-31.

Van Dam, R. M. et al. (2006). Coffee, Caffeine, and Risk of Type 2 Diabetes: A prospective cohort study in younger and middle-aged U.S. women. Diabetes Care, 29, 398-403.

Van Dieren, S. et al. (2009). Coffee and tea consumption and risk of type 2 diabetes. Diabetologia, 52, 2561-2569.

Wu, J. N. et al. (2009) Coffee consumption and risk of coronary heart diseases: a meta-analysis of 21 prospective cohort studies. International Journal of Cardiology, 137, 216-25.


Can caffeine improve performance?

Caffeine is one of the most extensively researched supplements that is well shown to improve exercise performance. Intakes of 3-6mg/kg body mass can improve muscular endurance, function and strength, sprinting, jumping, and throwing performance, as well as a wide range of aerobic and anaerobic sport-specific actions.

Does caffeine improve running performance?

Yes! 3-6mg/kg body mass caffeine has been consistently shown to have beneficial effects on running performance.

Does caffeine improve cycling performance?

Yes! 3-6mg/kg body mass caffeine has been consistently shown to have beneficial effects on cycling performance.

Does caffeine improve football performance?

Yes! 3-6mg/kg body mass caffeine before a football match can improve performance. Smaller amounts at halftime have also been shown to improve second-half performance.

Does caffeine improve strength training performance?

Caffeine intakes of 3-6mg/kg body mass before strength training can improve muscular endurance, function, and muscle strength, as well as other high-intensity explosive actions e.g. sprinting, jumping and throwing, that require maximal voluntary contractions.

How soon before training should I take caffeine?

The effects of caffeine are usually felt quickly and peak in the bloodstream 30-60 minutes after consumption from caffeinated drinks and tablets. Caffeinated gum has a faster response and can be taken closer to 10-20 minutes before.

How long do the effects of caffeine last?

Caffeine has an average halflife of 5 hours, meaning it stays in the system for up to ~10 hours, however it can range from 1-10 hours as some people do not respond to caffeine whereas others are very sensitive to it.

How long does coffee’s diuretic effects last?

Coffee is not a diuretic in low to moderate doses, but in large quantities it may cause diuretic effects in people who do not regularly drink coffee. These symptoms may last a couple of hours after consumption.

Is decaffeinated coffee a diuretic?

Decaffeinated coffee will have a very little to no diuretic effect as its caffeine content is significantly reduced to approx. 7mg per cup, whereas much larger intakes of over 300mg is likely when diuretic effects may occur.

How much caffeine is too much?

Four hundred grams per day of caffeine is considered safe for a healthy adult. But, people are recommended to drink less than that. However in certain circumstances (e.g. before the competition) where up to 6mg/kg caffeine is the maximum effective dose to improve performance in athletes, can be consumed safely in a single dose. A single dose of 9mg/kg is associated with impaired performance, so you can have too much of a good thing!

Is coffee a diuretic or laxative?

Coffee is not a diuretic in low to moderate doses, but in large quantities it may cause diuretic effects in people who do not regularly drink coffee. Coffee is likely to cause laxative effects however whether it is caused by the coffee or caffeine content is unclear.

Does coffee dehydrate your skin?

No coffee does not dehydrate your skin, especially if the caffeine content do not risk a daily consumption above 350mg.

Does drinking a single cup of coffee per day have any side effects?

Drinking a cup of coffee per day is relatively safe. The only side effect could be impaired sleep quality if it is consumed later in the day before bed. It is recommended to stop consuming caffeine after 2 pm to prevent sleep disturbances

How much coffee per day is healthy?

Up to 6 cups of coffee a day can have health benefits and is not recommended to consume more than this. More will not necessarily cause serious health complications as there’s no evidence to support this claim.

Can you die of caffeine overdose?

Yes, on extremely rare occasions, people can die of caffeine overdose. But, you do not have to worry about dying by drinking common caffeinated beverages as they contain a very low amount of caffeine.

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