A clinical case published in the British medical journal BMJ Case Reports has raised concerns about excessive consumption of energy drinks and their possible link to stroke , according to a study on heart health.
Far from being an anecdotal oddity, this episode serves as a starting point for European specialists and organizations such as the Spanish Agency for Food Safety and Nutrition (AESAN) to warn that the cardiovascular and neurological risk linked to these drinks is not being properly assessed , especially when consumed daily and in large quantities.
Much more than caffeine
In the case described by the British doctors, the patient went to the emergency room after noticing weakness and numbness on the left side of his body, problems maintaining his balance, and difficulty walking, swallowing, and speaking. The symptoms were consistent with ataxia, a motor coordination disorder that immediately raised suspicion of a serious neurological problem.
Imaging tests confirmed an ischemic stroke located in the thalamus , the brain region responsible, among other functions, for integrating sensory information and coordinating movement. Simultaneously, measurements revealed an extremely high blood pressure of 254/150 mmHg, values consistent with a severe hypertensive crisis and immediate life-threatening condition.
In the hospital, after 72 hours of treatment with several antihypertensive drugs, his systolic blood pressure dropped to around 170 mmHg. At first glance, this seemed like a reasonable improvement, and the man was discharged with medication to continue taking at home, which is common in cases of severe hypertension associated with a stroke.
However, in the following weeks, his blood pressure spiked again and remained high despite combining up to five different medications. It was this lack of response to standard treatment that led the medical team to review the patient's daily habits in detail , going beyond the typical battery of questions about tobacco, alcohol, or drugs.
During that second interrogation, the missing piece emerged: the man confessed to drinking an average of eight cans of energy drink daily, each containing about 160 mg of caffeine. In total, he was ingesting between 1.200 and 1.300 mg of caffeine per day, more than three times the maximum recommended limit for adults, which is 400 mg per day, according to caffeine guidelines.
When she was instructed to completely stop drinking these beverages, the response was remarkable: her blood pressure normalized and she was able to discontinue her antihypertensive medication . However, the neurological damage was not fully reversed; years later, she continues to suffer from numbness and partial loss of sensation in her left hand, foot, and fingers.
Hypertension due to excess caffeine
The report's authors emphasize that the patient did not associate his consumption of energy drinks with cardiovascular risk at all . This perception, they point out, is quite widespread: they are generally seen as harmless products to "energize" the body, but not as something capable of triggering a stroke or heart attack.
At the European level, a beverage is considered high in caffeine if it contains more than 15 mg of caffeine per 100 ml . Many energy drinks far exceed this threshold. A typical 250 ml serving might contain around 80 mg of caffeine, but some large cans or "extreme" formats can reach up to 500 mg in a single serving, equivalent to several espressos at once.
In Spain, the Ministry of Health defines these beverages as non-alcoholic products, usually carbonated, containing caffeine, carbohydrates, amino acids, vitamins, minerals, and plant extracts, as well as various additives. AESAN (the Spanish Agency for Food Safety and Nutrition) notes that 160 mg of caffeine per can is equivalent to approximately two espresso coffees , so eight cans a day would be equivalent to about 16 coffees.
The problem isn't just the dosage. As experts explain, the label reflects the amount of "pure caffeine," but the formula often contains "hidden caffeine" from other ingredients . Guarana, for example, contains approximately twice as much caffeine as a coffee bean, so the actual intake can be considerably higher than what's listed on the packaging.
Furthermore, these drinks contain compounds such as taurine, ginseng, and glucuronolactone . The researchers hypothesize that the interaction between all these stimulants enhances the overall effect on the cardiovascular and nervous systems, promoting sudden spikes in blood pressure, arrhythmias, and, in certain circumstances, an increased risk of stroke or heart attack.
Harmful effects of energy drinks
A review of studies published in the scientific journal Nutrients compiles a comprehensive list of adverse effects associated with high consumption of energy drinks, especially when consumed daily or in large quantities. Some are relatively common, while others are rarer but potentially fatal.
Among the most frequently reported problems are sleep disturbances (insomnia, frequent awakenings, poor sleep quality), anxiety, mood swings, and difficulty concentrating. In adolescents and young adults, heavy use has been linked to an increase in risky behaviors and behavioral disorders.
In the cardiovascular field, the literature reports numerous cases of arrhythmias, intense palpitations, and hypertensive crises after consuming several cans in a short period, especially in people with pre-existing risk factors or a particular sensitivity to caffeine. Cardiac arrest has been documented in some extreme cases.
The effects are not limited to the heart: acute inflammation of organs such as the liver, stomach, pancreas, and kidneys , as well as dermatitis and certain autoimmune disorders, have also been described in association with intensive use of these products. Although establishing a cause-and-effect relationship is not always easy, the pattern is repeated in a large number of clinical reports.
Sugar is another major culprit. A single can of energy drink can contain between 27,5 and 30 grams of simple sugars per 250 ml , and up to 55-60 grams in 500 ml cans. This means that a single can can easily exceed the WHO's daily recommendations, which advise that free sugars should not represent more than 10% of total daily energy intake.
Prolonged consumption of high amounts of sugar has been linked to overweight, obesity, type 2 diabetes, tooth decay, alterations in the gut microbiota, and an increased risk of cardiovascular disease . Potential effects on cognitive performance and learning difficulties in childhood have also been noted, as well as a greater likelihood of developing cognitive impairment and Alzheimer's disease in the long term.
An underestimated risk in young people
Although the case that has made headlines is that of a middle-aged man, experts insist that the most vulnerable group is teenagers and young adults , the main consumers of these types of drinks in Europe, as shown by the surge in consumption among minors . Much of the advertising and promotions are specifically targeted at them.
In the UK, some large supermarkets have decided not to sell energy drinks to children under 16 in an attempt to curb obesity, tooth decay, and other health problems linked to excess sugar. However, cardiovascular and neurological risks remain less prominent in the public debate.
In Spain, the Ministry of Consumer Affairs requires that products exceeding a certain caffeine content include a visible warning such as: “High caffeine content: not recommended for children or pregnant or breastfeeding women .” However, there is currently no sales ban for minors nor any specific regulation limiting the amount that can be purchased.
AESAN and the Ministry of Health recommend that children, adolescents, pregnant women, breastfeeding mothers, and people with hypertension, cardiovascular disease, or sleep disorders completely avoid these beverages. Healthy adults are advised to consume them very infrequently and in small quantities, always consulting their doctor if taking other medications.
Spanish experts also emphasize that energy drinks should not be used for rehydration after exercise or as a substitute for rest. They also advise against combining them with alcohol, as the mixture can mask the feeling of intoxication and encourage risky behavior, traffic accidents, and excessive consumption of both substances.
Stricter regulation
The Nottingham clinical case, along with the accumulated literature, has led several specialists to propose more ambitious regulatory changes in Europe and Spain . Although the evidence does not yet allow us to categorically state that energy drinks cause strokes on their own, a worrying association has been observed in contexts of excessive consumption.
The authors of the British report propose that, just as tobacco, alcohol or drug use is routinely investigated, healthcare professionals should specifically ask about energy drinks when treating patients with hypertension, arrhythmias or other seemingly unexplained cardiovascular problems.
From a public health perspective, there is growing support for stricter labeling, limiting advertising aimed at minors, and considering sales restrictions , especially in schools, sports facilities, and environments frequented by teenagers. Some experts even suggest equating certain warning messages with those already found on alcoholic beverages.
Organizations like AESAN (Spanish Agency for Food Safety and Nutrition) point out that beverages high in caffeine and sugar are not only linked to stroke and cardiovascular disease, but also to an overall increase in morbidity from metabolic and digestive disorders. Therefore, they urge the strengthening of information campaigns so that the public better understands what they are consuming when they open a can of these types of products.
In the clinical setting, the case of the British man has also served to highlight "the importance of targeted questioning" about these consumption habits in daily practice. Many patients, like him, do not consider it relevant to mention that they consume several energy drinks a day, which can delay the diagnosis of the cause of severe hypertension or other alarming symptoms.
Based on current knowledge, the medical community agrees that energy drinks, combining high doses of caffeine, sugar, and other stimulants , are far from harmless if consumed excessively. The published case, the warnings from AESAN (Spanish Agency for Food Safety and Nutrition), and regulatory initiatives in various countries all point in the same direction, highlighting the need to moderate their consumption, especially among young people, before serious health problems arise such as strokes or other severe complications.
