This blocks the path of the sedating adenosine in the brain, with the result being that we feel perky and alert. As a result, it slows down nerve cell activity, making us feel drowsy and tired.īut caffeine, which chemically is similar to adenosine, sticks to these receptors, too. Normally, our levels of adenosine rise during the day and it binds to these receptors. It has this effect because it blocks the action of a chemical called adenosine, which is naturally produced in the body, mainly in the liver.Īdenosine binds to receptors that are found on cells around our bodies - including nerve cells in the brain, where they play a part in our sleep/wake cycle. Indeed, while we tend to think of caffeine as being present in just tea or coffee, in its pure form it's found in 60 different plants, from the kola nut to cacao.Ĭaffeine has some surprising health benefits - for example, it's been linked to a reduced risk of some types of skin cancer (more on this later) - but it is best known, of course, as a stimulant, which kicks us awake and improves our focus. Even if you feel you can 'hold' your caffeine well, there are good reasons to limit itīut as a standard cup of instant coffee contains around 100 mg (takeaway coffees may contain three times this), a mug of tea around 55 mg and even a bar of dark chocolate around 80 mg per 100 g, it can soon add up.
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