Drinking several strong energy drinks every day may pose a serious stroke risk, authors of a case report warn after treating an otherwise fit and healthy man in his 50s with a daily 8-can habit and very high blood pressure. The findings prompted the authors to call for tighter regulation of the sales and advertising of energy drinks, particularly given their popularity among young people.

The man had a stroke in his thalamus—the part of the brain involved in sensory perception and movement. His symptoms included left-sided weakness, numbness, as well as difficulties with balance, walking, swallowing and speech—collectively known as ataxia.

On admission to the hospital his blood pressure was 254/150 mm Hg, which is considered extremely high. He was started on drugs to lower his blood pressure, and his systolic blood pressure—reflecting arterial pressure during the heart’s pump action—fell to 170 mm Hg. But once back home, his blood pressure rose again and remained persistently high despite the ramping up of his drug treatment.

On further questioning, he revealed that he drank an average of 8 energy drinks every day, each of which contained 160 mg of caffeine, adding up to a daily intake of 1200-1300 mg of caffeine. The recommended maximum daily intake is 400 mg.

He was asked to give up this daily habit, after which his blood pressure returned to normal and blood pressure-lowering drugs were no longer needed. But he didn’t regain full feeling on his left side.

The authors note that the man’s lack of awareness about the potential cardiovascular risks associated with heavy energy drink consumption is probably not surprising, as the drinks aren’t generally thought of as a potential cardiovascular disease risk. They highlighted that many energy drinks contain more than 150 mg of caffeine per liter and typically have a very high glucose-based sugar content and varying quantities of other chemicals.

The declared amount is the “pure caffeine,” but other ingredients contain “hidden caffeine”— for example, guarana is thought to contain caffeine at twice the concentration of a coffee bean.

“The hypothesis is that the interaction of these other ingredients, including taurine, guarana, ginseng and glucuronolactone, potentiates the effects of caffeine-heightening stroke and [cardiovascular disease] risk through numerous mechanisms,” they explained.

“The average [energy drink] is said to contain around 80 mg of caffeine per 250 ml serving, compared with 30 mg in tea and 90 mg in coffee, but in some cases can contain up to 500 mg in a single serving,” they point out.

To read the abstract of the study, published in BMJ Case Reports, click here