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Caffeine in Health and Endurance Exercise

Caffeine is the most widely used stimulant on the planet and drinks containing it have been consumed for thousands of years. Its primary activity is as an adenosine receptor antagonist and it brings about a number of physiological changes including increased heart rate and heightened wakefulness. These properties have implications both in day to day life and exercise performance.

Caffeine and Health

Caffeine consumption is widely understood to increase alertness and reduce fatigue. Furthermore, caffeinated drinks also help maintain hydration and are included in the current UK recommendations on fluid intake. Although the acute effects of caffeine consumption are largely beneficial, high doses can impair sleep and increase risk of anxiety. A number of compounds found in teas and coffees also impair absorption of non-haem iron (such as found in plant based iron sources), and so should be avoided around meal times for individuals with a low intake of haem iron such as vegetarians.

As well as the short term effects of consuming caffeinated drinks, there is increasingly evidence that inclusion of tea and coffee in the diet may have protective effects against a range of chronic diseases. Although a causative role is yet to be proven, a number of large epidemiogical studies have found associations between tea and coffee consumption and health. Tea for instance is associated with reduced risk of cardiovascular disease and cancers, whilst coffee consumption is associated with reduced all-cause mortality and risk of diabetes. Alongside caffeine, teas and coffees contain a wide range of other bioactive substances including polyphenols, diterpenes and melanoidins, many of which have antioxidant properties. These compounds have been suggested as a possible mechanism underlying the health benefits of tea and coffee.

Caffeine and Endurance Exercise

Caffeine is one of a very small number of supplements with a strong body of evidence supporting its use in endurance sports. It can be consumed in a variety of forms including from coffee or tablets before exercise, and in gels or drinks during exercise. There are huge variations in caffeine content between different sources, so it is worth checking dosage before use. We also recommend avoiding caffeine powder due to the risk of accidental overdose. Whilst coffee is often the best option from a health perspective, it does have its limitations in the context of competition– caffeine contents are quite variable (a range as wide as 48-317mg caffeine per serving has been reported) and therefore dosage is less controllable than when taken tablet form. The best option is often dependent on individual preference and the nature of the exercise they are undertaking. We recommend using coffee for the majority of training rides, but switching to tablets for competition.

As it has a relatively long half-life (6 hours on average) and rapid absorption (around 45 minutes to reach maximum blood concentration), a common strategy is to take a high caffeine dose of up to 6mg/kg bodyweight around an hour before competition. However, other strategies have also been shown to have ergogenic effects and high dose caffeine use does have a number of common side effects including gastrointestinal upset, mental confusion and inability to focus. This is particularly the case in individuals who have habitually low intakes. These adverse effects are less pronounced with lower doses around 3mg/kg bodyweight, so having a low dose before exercise and ’topping up’ during can be a viable alternative, especially during longer events. Furthermore, ingestion of low caffeine doses late in exercise (2mg/kg bodyweight 30 mins prior to the end) has been shown to be beneficial to performance. This can be achieved using gels or drinks, but be aware of variations in caffeine content between different products. High 5 caffeine gels for instance contain 30mg caffeine, whilst SIS contain 150mg. As there is also a wide range of tolerance between individuals, we advise trying out different strategies in training to find which is most effective for you.

Practical Guidance

  • Moderate caffeine consumption of up to 400mg / day ( roughly 3-5 coffees or 8 teas), is safe for healthy adults excluding pregnant women where 200mg / day (approximately 1.5-2 coffees or 4 teas) is the advised upper limit

  • Avoid added calories in caffeinated drinks during day-day life (eg. sugar sweetened energy drinks or adding sugar or cream to your hot drinks)

  • Using caffeine before exercise can have ergogenic effects, but try out a range of strategies in training before using them in competition

Further Reading

Guallar, E., et al. (2017). Moderate Coffee Intake Can Be Part of a Healthy Diet. Ann Intern Med. United States. 283-284.

Higgins, S., C. R. Straight and R. D. Lewis (2016). The Effects of Preexercise Caffeinated Coffee Ingestion on Endurance Performance: An Evidence-Based Review. Int J Sport Nutr Exerc Metab 26(3) 221-239.

Ludwig, I. A., et al. (2014). Variations in caffeine and chlorogenic acid contents of coffees: what are we drinking? Food Funct 5(8) 1718-1726.

Sokmen, B., et al. (2008). Caffeine use in sports: considerations for the athlete. J Strength Cond Res 22(3) 978-986.

Wikoff, D., et al. (2017). Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. Food Chem Toxicol 109(Pt 1) 585-648.

Zhang, C., et al. (2015). Tea consumption and risk of cardiovascular outcomes and total mortality: a systematic review and meta-analysis of prospective observational studies. Eur J Epidemiol 30(2) 103-113.

#nutrition #health #performance #supplements

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