Dylan Bowe – B.Sc.
Caffeine is the most widely used psychoactive substance and stimulant in the world, and for good reason. It is most commonly found in coffee or teas, but can also be synthesised in a lab to have in pill or powder form as a supplement. There are many benefits of utilizing caffeine, to improve both mental and physical performance – and this article will delve into the science behind the substance, why and how we should consume it, and its potential implications on health.
Adenosine is a neurotransmitter that promotes sleepiness and muscle relaxation, as the day progresses. When caffeine is consumed, it blocks adenosine receptors in the brain as it has a similar chemical structure – this in turn reduces the sensations of fatigue, tiredness and pain. Along with this, caffeine also increases dopamine levels, which has a mood enhancing and stimulating effect. This is the main mechanism behind caffeine’s ability to reduce mental fatigue, increase alertness and reduce reaction time. These effects occur in moderate doses between 40-300mg, and also have been observed in people who are non-habitual caffeine/coffee drinkers.
There have been concerns that coffee and caffeine may increase risk of cancer and cardiovascular disease, but recently many health benefits have emerged. Also, an issue is that coffee contains hundreds of biologically active phytochemicals such as polyphenols, melanoidins and the likes of magnesium, potassium and niacin (Ludwig et al., 2014). These coffee compounds may reduce oxidative stress (Correa et al., 2012), improve the gut microbiome (Jaquet et al., 2009) and modulate fat and glucose metabolism (Vitaglione et al., 2010). In contrast, the diterpene cafestol, which is found in unfiltered coffee, has been shown to increase cholesterol levels (Urgert and Katan, 1997). Therefore, research findings for coffees and other dietary sources of caffeine such as green teas should be interpreted carefully, since health effects may not be due to solely caffeine itself.
What are the benefits?
Caffeine shows well established benefits for enhancing athletic performance in both endurance based events and short term maximal tasks. Some recent research has suggested that the ergogenic effects of caffeine are influenced by the athlete’s variant of numerous genes, including the CYP1A2 gene involved in the metabolism of caffeine in the liver (Guest et al., 2018). This can explain the well-known variability in individual responses to the ‘social’ use of caffeine, confirming the need for athletes to both trial their intended performance uses of caffeine prior to implementation in competition and to take into account their personal history of reactions to caffeine intake in ‘everyday life’, such as effects on hear rate, jitteriness, sleep quality (Peeling et al., 2019).
Caffeine supplementation literature shows strong evidence of improved performance when consumed before events varying in duration from 5 to 150min (Ganio et al., 2009). Along with this, low to moderate doses of caffeine (100-300mg) consumed during endurance exercises (after 15-80min of activity) have been shown to enhance endurance performance by 3-7% (Paton et al., 2015). Caffeine ingestion 60 minutes prior to short term supramaximal events (specifically sprint events lasting 1-2min) may also improve performance upwards of 3%. Therefore, there is strong support for caffeine use for high performance track and field athletes in sprints, middle distance and endurance/ultra-endurance events.
Caffeine can also contribute to pain reduction when added to analgesic medications, such as paracetamol, and this is confirmed in a recent review stating an addition of 100-130mg caffeine can improve pain relief in patients (Derry et al., 2014), which may be an important consideration when recovering from injury and feeling pain. Caffeine may also increase the rate of glycogen replenishment when it is consumed with glycogen during exercise, which may be important for athletes with a busy training schedule or taking part in multi-day competition. Along with physical performance benefits, caffeine also improves cognition which includes mood, focus, alertness and memory, by increasing catecholamine signalling (adrenaline and dopamine).
How much should I take?
Caffeine doses of 3-6mg/kg body mass consumed roughly 60min prior to exercises in the form of anhydrous caffeine (i.e. pill or powder form) are commonly shown to result in optimal performance gains, but coffee/tea may also be used. There is a lot of variance in caffeine levels in coffee – a typical espresso has 70mg, while a brewed filter coffee may have closer to 200mg, so take this into consideration and use trial and error if you decide to use coffee prior to exercise, and for standardisation, try to use the same form of coffee and then you can increase/decrease the amount depending on the desired amount. For a 60kg athlete, this dose would be anywhere from 180-360mg caffeine, but it may be wise to start on the lower end as there is extremely high individual variation on caffeine’s effects on the body.
As expected from its effects on fatigue, caffeine consumption later in the day can increase sleep latency (time to fall asleep) and reduce sleep quality (Clark and Landolt, 2017). Caffeine has a half-life of 6 hours, meaning if you consume 200mg at 12pm, there is still 100mg in your system by 6pm. It is advised to cut off caffeine as early as possible (prior to 2-4pm) to minimise the negative consequences on sleep. In high doses such as 400mg or more, it may induce anxiety which is often why people begin to feel ill or full of jitters after high amounts of caffeine. A high intake can stimulate urine output, but there is no detrimental effects on hydration even with long term moderate doses of caffeine (<400mg/day).
Overall, caffeine the most accessible performance enhancing substance, and if you don’t feel any adverse side effects of consuming it and want to improve your performance, you should consider supplementation. It has been shown to improve aerobic performance, time trial performance, reduce the perceived rate of exertion on exercise, increase power output and enhance mood, clarity and decision making. Sticking to the dosage guidelines is important, as there is unpleasant side effects of caffeine overconsumption – poor sleep quality, jitters, feeling of anxiety, along with some withdrawal symptoms when quitting after habitual use, such as headaches, fatigue, decreased alertness and depressed mood.
To get the most out of supplementation, a caffeine tolerance break may be used every few weeks or months, depending on how often you consume it, as this will allow your body to become more sensitive to its effects and thus allow you to consume less to get the same feeling.
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Clark, I. and Landolt, H.P., 2017. Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials. Sleep medicine reviews, 31, pp.70-78.
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Paton, C., Costa, V. and Guglielmo, L., 2015. Effects of caffeine chewing gum on race performance and physiology in male and female cyclists. Journal of Sports Sciences, 33(10), pp.1076-1083.
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Urgert, R. and Katan, M.B., 1997. The cholesterol-raising factor from coffee beans. Annual review of nutrition, 17(1), pp.305-324.
Vitaglione, P., Morisco, F., Mazzone, G., Amoruso, D.C., Ribecco, M.T., Romano, A., Fogliano, V., Caporaso, N. and D’Argenio, G., 2010. Coffee reduces liver damage in a rat model of steatohepatitis: the underlying mechanisms and the role of polyphenols and melanoidins. Hepatology, 52(5), pp.1652-1661.