Most of us are drug addicts. This might seem like hyperbole but if you enjoy caffeine on a daily basis, then you are very likely addicted to it. If you don’t believe me then try a little self experimentation and stop taking caffeine and see how you feel. I tried it and the symptoms were relatively mild but nevertheless classic of withdrawal; headache, insomnia, irritability and a craving for some coffee. Okay, caffeine is not addictive like cocaine or heroine, but nevertheless it is a stimulant of the central nervous system. If you want to give up caffeine then you will find it much easier to withdraw slowly by reducing your intake day by day until you are caffeine-free. For most of us however, caffeine doesn’t do much harm in the amounts of everyday use. A cup of tea, on average, contains around 10 thousandths of a gram (10 milligram, abbreviated to mg) of caffeine. If the 10 mg of caffeine were isolated from a cup of tea, then it would look like ten grains of table salt, in both amount and colour. A double shot of espresso might contain approximately 150 mg and even the decaf equivalent contains around 10 mg. The term ‘decaf’ is a little misleading in this respect perhaps. A Starbuck’s Grande coffee is reported to have around 300 mg of caffeine and if you are not used to that amount, it is likely to give you quite a buzz. Comparing weight on weight, black tea contains more caffeine than coffee but because of the amounts used in the brew, a cup of tea has less caffeine than coffee.
Chocolate also contains caffeine but the amounts are quite small with a whole 100 g bar of dark chocolate containing around 50 mg (milk chocolate is about half this amount). You would have to eat over half a kilogram of milk chocolate to get the same amount of caffeine as a double espresso and this is not accounting for throwing up after eating so much chocolate in one go.
Although the amount of caffeine in chocolate is low, it does contain another stimulant of the central nervous system closely related to caffeine called theobromine. (Theobromine by the way, has nothing to do with bromine or bromide, it just got this name because of its colour). When you ingest caffeine, some of it gets metabolised in the body to form theobromine although I could not find any evidence that the metabolism works the other way round. Theobromine is pharmacologically active and is a banned drug for race horses, although horses are more susceptible to effects than people. Grooms have to take care not to give chocolate treats to horses or they could fail a drug’s test.
Like anything, too much caffeine can be toxic and indeed it has caused a few deaths but mostly under unusual circumstances. As a relatively recent example, in 2013 John Jackson of the West Midlands in the UK tragically died after overdosing on Hero Instant Energy Mints. Each mint contained 82 mg of caffeine and John Jackson could have consumed as many as 300 over 24 hours. Although tragic for John Jackson and his family, consuming this number of mints can’t really be seen as an everyday occurrence. Nevertheless, it is a cautionary tale as although we are aware that tea and coffee contain caffeine it may not be so obvious in the case of mints bought in the local sweetshop (the packaging did contain warnings). Another example product that contains caffeine where it may not be entirely obvious, is the majority of carbonated canned drinks. A can of typical cola for example, contains around 40 mg.
It’s a little tricky to estimate because values vary but the average person in good health would require around 8 g of caffeine to stand a good chance of dying from a caffeine overdose. This is the equivalent of 200 cans of cola which sounds a lot but in 2010 a 30-year old New Zealander, Natasha Harris, died of a heart attack which was attributed to drinking between eight to ten litres of coca-cola per day. The consumption of coca-cola would have been equivalent to just over a gram of caffeine per day. This level of consumption is classified as addiction - it even has a specific name of caffeinism. The volume of carbonated fluid would also be pretty unhealthy and so even in these amounts caffeine was probably not entirely to blame.
The moral of all this is that everyday items of diet can contain pharmacologically active substances which taken in the appropriate amounts will do no harm. Anything taken in excess however can be harmful and so just watch the consumption and you should be fine. With all this writing, I’m now off to have a cup of tea.