When we think of caffeine, the first things that comes to mind are drinks like coffee, teas or various fizzy drinks and quite rightly so.

Caffeine* is a mild central nervous system stimulant and can also be found in various plants-materials like coffee and cacao beans, guarana berries, tea leaves and kola nuts (2). It is still a mystery how the effect of caffeine has been discovered. One legend talks about a shepherd who saw his goats behaving strangely after eating coffee berries. While, the truth remains unknown, coffee consumption actually started by eating whole beans (3).

Worldwide adults consume 37-360 mg caffeine per day (4). Raw coffee beans contain 1.20-2.40 g caffeine per 100 g (5). In most European countries coffee is the predominant source of caffeine, contributing to 40-94% of the intake (6). A large cup (240 ml) of brewed coffee contains 102-200 mg caffeine, while a large cup (240 ml) of tea contains 40-130 mg caffeine, depending on the type (7).

Caffeine works by blocking the action of adenosine at the receptor level (8). Adenosine is one of the most powerful substances in the body (it could be called the “tiredness molecule”). It is associated with food intake and reduces communication between nerve cells (e.g. in the brain) (3, 8). Some adenosine receptors can’t spot the difference between adenosine and caffeine, so when we consume caffeine, it attaches to receptors preventing adenosine from doing so. Without adenosine, brain activity improves. That’s why caffeine can make you feel more alert, especially when more than 75 mg is consumed, for example it improves reaction time (9, 10). In addition, research has shown that when sportsmen and women take caffeine before, during or after exercise they may benefit in several ways. These include:

• Increased performance; or perform at a higher level
• Increased endurance capacity; able to maintain a certain pace for longer
• Better performance during a prolonged interval training or tournament
• Better and quicker recovery

In order for  these effects to be felt, it’s recommended that you should consume more than 3 mg caffeine/kg bodyweight at least 1 hour before exercising (11, 12). In addition to this, caffeine may also influence our body’s energy usage; it is estimated that 1 mg caffeine may increase daily energy expenditure by ±0.1 kcal (13, 14).

Caffeine is so much more than the common flavouring substance that we find in our cups of coffee or tea. It has so many advantages and can even affect the way athletes and gym goers perform, exercise and train.

*Consumption of up to 400 mg/day is safe for healthy adults (200 mg for pregnant & breastfeeding women) day [1.          EFSA. Scientific Opinion on the safety of caffeine. EFSA Journal. 2015;13 (5): 4102.

References

1. EFSA. Scientific Opinion on the safety of caffeine. EFSA Journal. 2015;13 (5): 4102.
2. McLellan TM, Caldwell JA, Lieberman HR. A review of caffeine’s effects on cognitive, physical and occupational performance. Neuroscience & Biobehavioral Reviews. 2016;71:294-312.
3. Fredholm BB. Methylxanthines: Springer Science & Business Media; 2010.
4. Verster JC, Koenig J. Caffeine intake and its sources: A review of national representative studies. Critical reviews in food science and nutrition. 2018;58(8):1250-9.
5. Andrea Illy RV, ,. Espresso Coffee, the science of quality: Elsevier ACademic Press; 2005.
6. EFSA. EFSA explains risk assessment. Caffeine2015. Available from: https://www.efsa.europa.eu/sites/default/files/corporate_publications/files/efsaexplainscaffeine150527.pdf.
7. Heckman MA, Weil J, De Mejia EG. Caffeine (1, 3, 7‐trimethylxanthine) in foods: a comprehensive review on consumption, functionality, safety, and regulatory matters. Journal of food science. 2010;75(3):R77-R87.
8. Smith A. Effects of caffeine on human behavior. Food and chemical toxicology. 2002;40(9):1243-55.
9. EFSA. Scientific Opinion on the substantiation of health claims related to caffeine and increased fat oxidation leading to a reduction in body fat mass (ID 735, 1484), increased energy expenditure leading to a reduction in body weight (ID 1487), increased alertness (ID 736, 1101, 1187, 1485, 1491, 2063, 2103) and increased attention (ID 736, 1485, 1491, 2375) pursuant to Article 13 (1) of Regulation (EC) No 1924/2006. EFSA Journal. 2011;9(4):2054.
10. Konishi Y, Hori H, Ide K, Katsuki A, Atake K, Igata R, et al. Effect of single caffeine intake on neuropsychological functions in healthy volunteers: A double-blind placebo-controlled study. PloS one. 2018;13(10):e0202247.
11. EFSA. Scientific Opinion on the substantiation of health claims related to caffeine and increase in physical performance during short-term high-intensity exercise (ID 737, 1486, 1489), increase in endurance performance (ID 737, 1486), increase in endurance capacity (ID 1488) and reduction in the rated perceived exertion/effort during exercise (ID 1488, 1490) pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal. 2011(9(4)):2053.
12. Southward K, Rutherfurd-Markwick KJ, Ali A. The effect of acute caffeine ingestion on endurance performance: a systematic review and meta–analysis. Sports Medicine. 2018;48(8):1913-28.
13. Belza A, Toubro S, Astrup A. The effect of caffeine, green tea and tyrosine on thermogenesis and energy intake. European journal of clinical nutrition. 2009;63(1):57-64.
14. Hursel R, Viechtbauer W, Dulloo AG, Tremblay A, Tappy L, Rumpler W, et al. The effects of catechin rich teas and caffeine on energy expenditure and fat oxidation: a meta‐analysis. Obesity reviews. 2011;12(7):e573-e81.