Caffeine is a natural part of everyday life for many people. It is found in coffee, tea, and energy drinks and is consumed daily by the majority of the adult population.
The substance is legal, widely accepted, and often associated with increased energy and improved concentration.
Nevertheless, caffeine can affect the body in ways that are rarely discussed.
A widely used stimulant
According to Ulf Ellervik, a professor of organic chemistry at Lund University, around 90 percent of the world’s adults consume caffeine.
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The substance works by suppressing the body’s signals of fatigue, making people feel more alert.
At higher intakes, however, caffeine can cause side effects such as restlessness, tremors, and sleep problems.
These effects are well known but are usually perceived as temporary and harmless.
The body’s chemical balance
Ulf Ellervik explains to Forskning & Framsteg that caffeine can also affect the balance between sodium and potassium in the body.
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Potassium is important for nerves and muscles, including the heart.
Since almost all potassium is located inside cells, the level in the blood can change rapidly.
In some cases, this can lead to serious symptoms such as muscle weakness and heart palpitations.
A case with open questions
In the autumn of 2025, four employees at Akademiska Hospital in Uppsala, Sweden, became acutely ill within a short period.
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Among other symptoms, they experienced heart palpitations and tremors and were found to have very low levels of potassium in their blood.
The case is being investigated as a possible poisoning, and an unusually high intake of caffeine has been mentioned as a possible explanation, though this has not been confirmed.
According to Ulf Ellervik, caffeine poisoning is rare and requires extremely large amounts.
For most people, moderate consumption is therefore not associated with risk. However, the case shows that concentrated forms of caffeine may give rise to new considerations.
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Sources: Forskning.no, and Forskning & Framsteg.
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