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Caffeine: a pick-me-up for billions

Foods and drinks containing caffeine have always been consumed not only for their taste, but also for their stimulating qualities. But how much is too much?

Caffeine has been popular for a long time around the globe. Around 80 percent of the world's population consume coffee, tea, cocoa or chocolate, cola or energy drinks at least once a day. There are also many other drinks, food or food supplements such as capsules, powders and bars to which caffeine, for example from guarana, is added. In Europe, however, coffee is the predominant source of caffeine for adults, accounting for 40 to 94 percent of total intake. Only in Ireland and the UK is tea ahead, contributing just under 60 percent of total caffeine intake. For adolescents, the main sources vary greatly between countries: in some it is chocolate, others coffee, cola drinks or tea. Chocolate, including cocoa-based drinks, is the number one source of caffeine for children aged three to ten in most countries, followed by tea and cola drinks.

Quick hit

Caffeine can improve alertness, concentration and attention and yet still lead to relaxation. This is the case with moderate consumption, i.e. individual doses of 50-200 milligrams. The stimulating effect usually sets in 15 to 30 minutes after ingestion and can last for several hours. On average, healthy adults have excreted half of the caffeine after about four hours. However, the range for this half-life is large, from two to eight hours, and is influenced by many factors such as age.

Dehydration myth

There is a persistent myth that caffeine dehydrates the body (which is why a glass of water is served with coffee in many European countries). While it is true that caffeine can lead to an increased urge to urinate in the short term, that is only when more than about 300 milligrams of caffeine has been consumed. However, if you regularly consume caffeinated beverages and foods, your body quickly gets used to the amount of caffeine and the urge to urinate decreases.

A question of dosage

Negative short-term effects can occur in children and adults who consume very high individual doses, for example if about 400 to 800 milligrams are consumed at once. This can result in nervousness, anxiety, aggression, sleep disorders and palpitations. In the case of chronic excessive caffeine consumption, cardiovascular problems are sometimes observed, and in pregnant women the growth of the foetus may be stunted. A detailed safety and risk assessment of caffeine was conducted by the European Food Safety Authority (EFSA) in 2015. Its key points are:

  • Over an entire day, up to 400 milligrams of caffeine from all sources is safe for adults. This amount corresponds to about five cups of coffee. However, it is not possible to state this exactly because the caffeine content of coffee, like that of chocolate, varies greatly depending on the production process, the type of coffee/cocoa beans used, preparation (for example, filter coffee or espresso) and the quantity used.
  • During pregnancy and breastfeeding, up to 200 milligrams of caffeine per day has no negative consequences for the child.
  • If caffeine is ingested shortly before bedtime, single doses of 100 milligrams can delay some adults falling asleep and shorten the duration of sleep.
  • For children (three to ten years) and adolescents (ten to 18 years), three milligrams per kilogram of body weight is considered a daily tolerable upper limit. A child weighing 20kg should therefore not consume more than 60 milligrams of caffeine per day. This amount is contained in a small bottle of iced tea. A 65-kilogram teenager reaches their maximum dose of 195 milligrams of caffeine with two cans of energy drinks and half a bar of dark chocolate.

No camouflage effect

When the combination of alcohol and caffeine is discussed, talk often revolves around energy drinks. However, that particular discussion also applies to Caffè Corretto, tea-based punch or hot chocolate with rum. The evaluation conducted by EFSA notes that in this respect an intake of 200mg of caffeine is unlikely to mask or hide the subjective perception of drunkenness. When seen the other way round, alcohol consumption that results in a blood alcohol level of about 0.8 milligrams per millilitre has no influence on the harmlessness of an intake of up to 200mg of caffeine. Other ingredients usually found in energy drinks, like taurine or glucuronolactone, probably do not have negative interactions with caffeine and alcohol either.


Marlies Gruber
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