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What is Caffeine?

Caffeine is used by athletes around the world. Where does it come from and how does it affect performance?

Caffeine (also known as 1,3,7-rimethylxanthine) is often described as ‘the most commonly used drug in the world.’ It is a stimulant found in a variety of food and drinks that affects the central nervous system and also has a wide variety of effects across the body.


What is Caffeine Infographic


What effects does caffeine have in the body?

After being consumed, caffeine reaches its peak levels in the blood after 30 to 60 minutes. Some of caffeine’s effects can be felt, such as improved mental alertness, reduced sensations of fatigue and reduced drowsiness, and these were the earliest observed effects of caffeine. Caffeine also has effects which are not as noticeable, such as increased production of epinephrine (adrenaline), often known as the ‘fight or flight’ hormone which causes a temporary increase in blood pressure and heart rate. The increased adrenaline can result in small increases in energy expenditure (calorie burning) and in some scenarios, more fat being used for energy.


What foods contain caffeine and how much?

Caffeine is found naturally in over 60 plants, but the main sources for humans in the diet are coffee, tea (green and black), maté and cocoa. Some supplements and medications also contain caffeine, often in higher amounts than in most food and drinks. Coffee is by far the biggest source of caffeine in the diet, with a cup containing around 100mg. However, the amount of caffeine in coffee varies very widely, depending on the type (instant or ground), how it is prepared, the beans it is made from and how they are roasted. One study showed that in different European coffee shops, one espresso contained anywhere from 48 to 317mg per serving. Therefore, a ‘cup of coffee’ is not a reliable measurement for caffeine. Both green and black tea contain 30-50mg of caffeine, which is similar to a can of regular or diet cola. Chocolate also contains some caffeine, with a 30g (~1 oz) serving usually containing less than 35mg. Dark chocolate contains more than milk chocolate, but both are relatively low in caffeine. Although some research is conflicting, it appears that caffeine from any source (such as coffee) can be as effective as a caffeine pill, as the caffeine is the same molecule regardless of its source.


Does caffeine affect performance?

Caffeine can improve exercise performance in a variety of exercise types, ranging from aerobic endurance exercise to lifting weights. It can reliably increase exercise performance in shorter and longer events, in multiple exercise types, including running, swimming and cycling. The International Olympic Committee (IOC) stated that caffeine is one of the few supplements with enough high-quality evidence to support marginal gains in performance (more detail on how caffeine affects performance can be read here ("How Does Caffeine Work?")


Is caffeine legal?

Caffeine is legal in one form or another, everywhere in the world. However, some countries have rules about the sale of caffeine-containing products and may limit the amounts that can be put into supplements. The World Anti-Doping Agency included caffeine on its banned substances list from 1984-2004, limiting athlete’s caffeine intake. However, it was removed as the amounts needed to improve performance were indistinguishable from amounts normally in the diet.


What are the side effects of too much caffeine?

Taking caffeine can have side-effects, including anxiety, headache, insomnia and restlessness - but they are normally associated with taking too much caffeine. The Food and Drug Administration states 400mg per day to be an amount not associated with side effects, but all individuals are different, meaning some people could have lower limits for side effects. It is possible to take so much caffeine that any benefit to performance is lost. Therefore, individuals should determine what dose of caffeine is effective and does not cause side-effects for them.


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