Caffeine: What is it, what does it do and where do we find it?
Before looking into the potential benefits for athletic performance, it’s important to understand exactly what caffeine is, the physiological response that caffeine ingestion causes and the most common products we find caffeine in. Caffeine is a natural chemical found in a variety of different plant sources. It is a psychoactive substance (don’t worry your cup of coffee isn’t going to land you 10 years in HMP Belmarsh), meaning it has an impact on how our brain works. Caffeine blocks the action of an important neurotransmitter in our brain called Adenosine by stopping it binding to receptors (think of placing a piece of paper between two bits of
Velcro, preventing them “sticking together”).
Adenosine plays an important function in our bodies sleep-wake cycle, as it builds up during the daytime, helping us to feel progressively more tired and lowering our. heart rate as we prepare for sleep in the evening. Caffeine blocking the adenosine binding to receptors causes reduced feelings of tiredness, coupled with potential dopamine and norepinephrine responses, we feel a heightened sense of alertness and focus when we consume caffeine (1).
Caffeine intake can come from a variety of food and drinks, the most common of which we often associate with is the humble cup of tea or coffee. The most popular drink worldwide, around two billion cups of coffee are consumed every day, with the UK consuming 98 million cups per day (2). Whilst our morning hot drinks are likely the most obvious source for many, caffeine is present in soft drinks, energy drinks, chocolate, sports drinks and in a variety of supplements. The amount of caffeine within products can vary significantly, so much so that even if you ordered the exact same drink from two different coffee shops, the chances are they will contain very different amounts of caffeine. Understanding the amount of caffeine in our food and drink choices is important for managing our intake, as well as understanding dosage for improved performance. The European Food Information Council provides the below as reference for our most common sources of caffeine:
- Tea (220 ml) – 50 mg
- Coffee (filter, one cup, 200 ml) – 90 mg
- Coffee (espresso, 60 ml) – 80 mg
- Standard can of energy drink (250 ml) – 80 mg
- Standard can of cola (355 ml) – 40 mg
- A bar of plain chocolate (50 g) – 25 mg
- A bar of milk chocolate (50 g) – 10 mg
Caffeine: Recommendations for the general population
The European Food Safety Authority (EFSA) provide guidance on caffeine consumption for the general population, stating that daily consumption of 400mg is unlikely to cause harm to a healthy adult consumer, that’s roughly 4 cups of tea. For women who are pregnant or breastfeeding, the recommendation is up to 200mg per day, due to the potential for caffeine to adversely effect the unborn child or breastfed infant (3).
Caffeine: Use as an ergogenic aid
Having discussed the benefits of caffeine, it seems obvious that many athletes seek to transfer the gains into sporting performance, making caffeine supplementation a popular strategy amongst groups from your regular gym-goer to your elite level athlete. Like all ergogenic aids, it’s critical to understand the correct amount, timing and potential side-effects of caffeine supplementation before implementing it into your exercise routine.
Supplementation with caffeine has been shown to produce small to moderate benefits on muscular endurance, movement velocity, muscular strength, sprinting, jumping and throwing performance, as well as a range of aerobic and anaerobic sports-specific actions. Aerobic endurance performance appear to demonstrate the more consistent and greater benefits from caffeine supplementation, although individual difference must of course always be considered. Caffeine has been shown to improve exercise performance at doses of 3-6 mg/kg body mass, in simple terms, a healthy 70kg male would aim to consume around 210mg-420mg of caffeine to see performance benefits. It’s worth noting that high doses of caffeine, for example 9mg/kg body mass, are often associated with higher number of side-effects and are not required to elicit performance gains (4), certainly worth considering next time you crack open two red bulls or add an extra scoop pre-workout into your routine!
Timing of caffeine supplementation within research studies is often focused around 60 minutes pre-exercise, whereby the most benefit appears to be shown; however, the source of caffeine ingestion needs to be considered as absorption rates will vary. Given the evidence, it seems like we should all be knocking back the espressos’, waiting an hour and then hitting the big PB’s right? As with any potential performance-enhancing substance, we’ve always got to consider the good and the bad. Caffeine’s ability to improve alertness and stave off sleep inducing natural responses can come with a price to our sleep quantity and quality, impacting our bodies ability to recover and potentially leading to a dependency on caffeine. It can also cause increased feelings of anxiety, restlessness, nausea and increased heart rate, all of which have to be taken into consideration before deciding to choose caffeine as your supplement of choice.
Another important consideration is the length of time it takes our bodies to metabolise caffeine, with a half-life (the amount of time it takes the body to process half the drug) of 3-5 hours (5), your 1pm coffee and 5pm tea are still impacting your bodies physiological responses well into the evening!
Summary1. Caffeine intake causes several physiological responses to the body, resulting in increased focus and alertness2. Caffeine within food and drink varies significantly and understanding the amount you are consuming is key3. Healthy adults should aim to consume no more than 400mg caffeine per day, with pregnant or breastfeeding women consuming no more than 200mg caffeine per day4. Caffeine is well documented as an ergogenic aid across a variety of aerobic and anaerobic sport-specific actions5. Timing, amount, and delivery method of caffeine must be considered prior to use as a supplement to enhance performance6. Caffeine intake has several potential side-effects that can impact physiological processes well after the initial consumption of product(s). Consideration of potential side-effects is key prior to use as a supplement.
Reference
1 Ferré, S. (2008), An update on the mechanisms of the psychostimulant effects of caffeine. Journal
of Neurochemistry, 105: 1067-1079.
https://doi.org/10.1111/j.1471-4159.2007.05196.x
2
https://britishcoffeeassociation.org/coffee-consumption/
3
https://www.eufic.org/en/whats-in-food/article/caffeine-qas
4 Guest, N. S., VanDusseldorp, T. A., Nelson, M. T., Grgic, J., Schoenfeld, B. J., Jenkins, N., Arent, S.
M., Antonio, J., Stout, J. R., Trexler, E. T., Smith-Ryan, A. E., Goldstein, E. R., Kalman, D. S., &
Campbell, B. I. (2021). International society of sports nutrition position stand: caffeine and exercise
performance.
Journal of the International Society of Sports Nutrition,
18(1), 1.
https://doi.org/10.1186/s12970-020-00383-4
5 https://sleepeducation.org/sleep-caffeine/
