Caffeine is almost ubiquitous in everyday life. It is found in the typical morning cup of coffee, in black tea, in cola, in energy drinks and even in chocolate.

“In moderate amounts, caffeine has a stimulating, positive effect,” explains biologist Dr. Anke Ehlers. In high doses, however, caffeine can cause sweating, anxiety and heart rhythm disorders, as well as affect the growth of the fetus in the mother’s womb. In extreme cases, severe overdoses from food supplements can even be fatal.

The general rule for adults is that a single dose of 200 milligrams of caffeine is not considered harmful to health. This is roughly equivalent to two cups of coffee, two cans of energy drink, four cups of tea, or five cans of cola.

Spread out over the course of a day, up to twice that amount—or 400 milligrams of caffeine per day—is considered unproblematic. However, the level at which adverse effects may actually occur varies from person to person. And those who, for example, regularly drink a lot of coffee tend to develop a higher tolerance level. However, they then need more coffee to still notice the positive effects.

Particular caution is advised when taking food supplements containing caffeine, which are sometimes used to enhance performance in sports. In this case, it is essential to follow the recommended dosage instructions, otherwise overdosing can easily occur.

“In particular, pure caffeine powder in loose form is problematic,” says BfR expert Ehlers. “It is in such a high concentration that you just can’t measure it with a kitchen scale.” The safe amount of 200 milligrams or 0.2 grams corresponds here to about a pinch. And just one or two teaspoons can be fatal.

For children and adolescents, the amount of caffeine that is still harmless to health is determined by body weight: a daily intake of 3 milligrams of caffeine per kilogram of body weight is therefore acceptable.

For younger children in particular, caffeine is mainly ingested through chocolate. However, to consume a dangerous amount of caffeine from sweets, a child would have to eat or drink a very large amount in a very short time.

“Taking a four-year-old child weighing around 17 kilograms as an example, they could just consume about 50 milligrams of caffeine,” says Ehlers. This amount is roughly equivalent to the caffeine content of two and a half bars of milk chocolate or half a liter of cola. “Of course, this is not a recommendation, not least because of the high sugar content, but rather the amount that is just safe in terms of caffeine concentration.”

Energy drinks contain about the same amount of caffeine as coffee. A 250-milliliter can contains an average of about 80 milligrams of caffeine. For teenagers, therefore, just three cans is enough to exceed the safe amount.

“Mixing energy drinks and alcohol can intensify the effects,” says Ehlers. “Both the caffeine and the alcohol affect the cardiovascular system and can cause heart rhythm disorders. When both factors come together, these negative effects could intensify.”

Provided by
BfR Federal Institute for Risk Assessment