Are energy drinks bad for you? What the heart data show

For a healthy adult, an occasional energy drink is unlikely to cause harm. But the caffeine-and-sugar load is not benign: in a randomised trial, drinking 32 ounces raised blood pressure and prolonged the heart's QT interval — a measure of electrical recovery — more than a placebo drink [s1]. For children and adolescents, the case is clearer still: paediatricians say the stimulants in these products have no place in their diet [s2].

What is in the can

Energy drinks combine caffeine, sugar and additives such as taurine and guarana, and they are marketed for alertness and performance. A review commissioned around European consumption patterns concluded that the health risks associated with energy drinks are "primarily related to their caffeine content," that the evidence for adverse effects when they are mixed with alcohol is growing, and that heavy consumption among young people is a public-health concern that has "largely gone unaddressed" [s3]. The review's central caveat is worth keeping: more research is needed on the long-term effects of the common ingredients, so the strongest evidence is about short-term, measurable changes rather than lifetime risk [s3].

The context that prompted the trials is not reassuring. The same randomised study notes that energy drinks have been linked to an increase in emergency-room visits and deaths, which is why controlled data on their cardiovascular effects were needed at all [s1]. That is an association drawn from surveillance rather than proof of cause, but it is the reason a laboratory trial went looking for a mechanism.

The heart signal, in a controlled trial

The most rigorous data come from a randomised, double-masked, placebo-controlled crossover trial in 34 healthy volunteers, average age 22.1 years [s1]. Each drank 32 ounces of one of two commercial energy drinks, or a placebo, within 60 minutes on three separate days with a six-day washout between [s1]. Investigators tracked the electrocardiogram and blood pressure at baseline and every 30 minutes for four hours [s1].

Both energy drinks prolonged the QT interval more than placebo. The maximum change from baseline in the Bazett-corrected QT interval was 17.9 milliseconds for drink A and 19.6 for drink B, against 11.9 for placebo (P = 0.005 across groups; P = 0.04 and P < 0.01 respectively versus placebo) [s1]. Peripheral and central systolic and diastolic blood pressure were also significantly higher than with placebo (all P < 0.001) [s1]. A prolonged QT interval matters because it is associated with a raised risk of dangerous heart rhythms; the effect here was modest and measured in young healthy people, but it is a real, dose-related change, not a theoretical one [s1].

Children and adolescents: a firm no

For younger consumers the guidance is unambiguous. A clinical report from the American Academy of Pediatrics reviewed the evidence and concluded that "caffeine and other stimulant substances contained in energy drinks have no place in the diet of children and adolescents" [s2]. The report also draws a distinction the marketing blurs: sports drinks and energy drinks are different products, and frequent or excessive intake of caloric sports drinks can substantially raise the risk of overweight or obesity in children and adolescents [s2]. The stimulant load is the reason energy drinks are singled out. The report goes further than a warning, encouraging clinicians to screen for sports and energy drink use during annual physical examinations and to improve education aimed at curbing their inappropriate use by young people [s2].

Where the real risk sits

The caffeine dose is the throughline, and it links these products to the same threshold that governs coffee and caffeine generally. A single large energy drink can approach an adult's recommended daily caffeine ceiling in one sitting, and the trial above shows what a 32-ounce dose does to a young heart in four hours [s1]. The added sugar is a separate load, carrying the metabolic and dental risks of any sugary drink. And caffeine sensitivity is not uniform: it is heightened in pregnancy and can provoke palpitations in susceptible people.

So the evidence does not support calling an occasional energy drink dangerous for a healthy adult. It does support treating a large or frequent intake as a genuine caffeine and blood-pressure exposure, keeping them away from children and adolescents [s2], and being cautious combining them with alcohol [s3] — while acknowledging the long-term picture is still thin [s3].

This article is informational and is not medical advice.

Sources

• Impact of High Volume Energy Drink Consumption on Electrocardiographic and Blood Pressure Parameters: A Randomized Trial — Journal of the American Heart Association, 2019
• Sports Drinks and Energy Drinks for Children and Adolescents: Are They Appropriate? — Pediatrics, 2011
• Energy Drink Consumption in Europe: A Review of the Risks, Adverse Health Effects, and Policy Options to Respond — Frontiers in Public Health, 2014