An energy drink is a caffeine delivery system with sugar, taurine and B vitamins attached. The caffeine is the part that does something, and in most cans it lands in the same range as a large coffee. The controlled trials that have measured blood pressure and cardiac electrical activity after energy drinks found real but small changes in healthy adults. The strongest objections are about who is drinking them, in what quantity, and what they are mixed with. This article separates what has been measured from what has been asserted, including claims this blog got wrong.
What is actually in the can
The label on a typical energy drink lists caffeine, sugar or a non-nutritive sweetener, taurine, glucuronolactone, guarana, and a stack of B vitamins. A 2021 review in Nutrients put the caffeine range at 75 to 240 mg per serving and taurine at roughly 342 mg per 100 mL.
The non-caffeine ingredients contribute much less than the label implies. Taurine is an amino acid the body makes itself and also gets from meat, dairy and seafood; Memorial Sloan Kettering’s summary of the human evidence describes mixed results across studies of exercise recovery, blood pressure and glucose control. Guarana is a caffeine source, so it is more caffeine under a different name. B vitamins are involved in energy-yielding metabolism, but the NIH Office of Dietary Supplements notes that B12 supplementation did not improve performance or endurance in people whose B12 status was already sufficient, which describes most drinkers.
A 2014 review in Nutrition Reviews by Mora-Rodriguez and Pallarés reached the same conclusion from the performance side: where energy drinks improved endurance, caffeine and carbohydrate were the plausible reason.
Caffeine, compared with coffee
The FDA’s position is that 400 mg of caffeine a day — about two to three 12-fluid-ounce cups of coffee — has not been associated with dangerous effects in healthy adults. It puts the threshold for toxic effects such as seizures at rapid consumption of around 1,200 mg.
Against that benchmark, most energy drinks are unremarkable. A 2024 market analysis in Proceedings of the Nutrition Society measured labelled caffeine across 18 caffeinated energy drinks and found a mean of 129 mg per serving, ranging from 70 to 160 mg.
| Source | Typical caffeine |
|---|---|
| Brewed coffee, 12 fl oz | Roughly 130–200 mg (FDA equivalence) |
| Energy drink, single serving | Mean 129 mg, range 70–160 mg |
| Energy drink, across the wider category | 75–240 mg per serving |
| FDA’s stated daily ceiling for healthy adults | 400 mg |
Two things follow. A single can is not a caffeine outlier, and the format matters more than the number: a chilled 16-ounce can goes down faster than a hot coffee, and multi-serving containers make 300 mg in ten minutes easy. The dose is ordinary; the delivery rate is not. Our piece on coffee and health covers the long-term cohort data on caffeine, almost all of it from coffee rather than energy drinks.
What the controlled trials measured
The relevant experiment is Shah and colleagues’ randomized, double-blind, placebo-controlled crossover trial, published in the International Journal of Cardiology in 2016, in which 27 healthy volunteers received an energy drink, a Panax ginseng preparation, or placebo. Two hours after the energy drink, the corrected QT interval had risen by 3.37 ms while placebo fell by 3.19 ms (p = 0.030), and systolic blood pressure had risen 2.00 mmHg against a placebo fall of 2.67 mmHg (p = 0.014). The between-condition differences were therefore roughly 6.6 ms of QTc and 4.7 mmHg of systolic pressure.
Those are statistically significant and clinically small. A few mmHg two hours after a caffeinated drink is what caffeine does, and six milliseconds of QTc sits well inside normal variation for a healthy adult. The finding is not nothing: it points at a specific group — congenital long QT syndrome, QT-prolonging medication, existing arrhythmias — for whom a small additional shift is not trivial.
Case reports, adverse event reports, and what they cannot show
This is where the previous version of this post went wrong. It led with “5 Hour Energy linked with 13 deaths, Monster linked with 5 deaths,” drawn from 2012 news coverage of adverse event reports filed with the FDA. An adverse event report states that someone consumed a product and something bad happened. It is a signal-detection tool. It is not an investigation, and it was never adjudicated as a finding of cause. Presenting those counts as a body count was wrong, and we are withdrawing it.
The population-scale counts have the same limitation. SAMHSA’s DAWN report recorded 10,068 US emergency department visits involving energy drinks in 2007 and 20,783 in 2011. In the 2011 figure, 58 percent involved an energy drink alone and 42 percent involved another substance as well — pharmaceuticals in 27 percent, alcohol in 13 percent, illicit drugs in 10 percent. The report states plainly that where another substance was on the chart, the energy drink was not necessarily the reason for the visit. The largest growth was in adults over 40, not teenagers, whose visits held roughly steady.
The same logic governs the case reports in the medical literature. There are published cases of arrhythmia, cardiac events and kidney injury following heavy energy drink consumption, sometimes with alcohol or other stimulants involved. Case reports are how signals get noticed. They cannot tell anyone how often it happens. No large prospective cohort has followed ordinary energy drink consumers for years the way the coffee cohorts did, so the population-level question is open rather than settled either way.
Adolescents, and why pediatric bodies singled this out
The strongest evidence-based objection to energy drinks is not about the drink. It is about the drinker.
Seifert and colleagues, reviewing the evidence in Pediatrics in 2011, reported that 30 to 50 percent of adolescents and young adults consumed energy drinks, that the caffeine content was high and largely unregulated, and that 46 percent of caffeine overdoses reported in 2007 occurred in people under 19. They concluded the drinks offered no therapeutic benefit to this group. The 2021 Nutrients review put adolescent consumption prevalence between 52 and 68 percent, against roughly 32 percent in adults.
The American Academy of Pediatrics went further in a 2011 clinical report, stating that caffeine and other stimulants in energy drinks “have no place in the diet of children and adolescents.” That report was retired in July 2021 under the AAP routine review cycle — a housekeeping step rather than a reversal, but worth stating rather than quoting a retired document as current policy. The FDA’s consumer guidance still advises against energy drinks for children and adolescents, and the Dietary Guidelines advise no caffeinated beverages under age 2.
The reasoning is straightforward. The same can delivers a larger dose per kilogram to a smaller body, tolerance is lower, and caffeine late in the day costs sleep at an age when sleep is doing more work.
Caffeine with alcohol
Mixing the two is the use case with the clearest regulatory history. In November 2010 the FDA warned four manufacturers that caffeine added to their alcoholic malt beverages was an unsafe food additive, ending the pre-mixed caffeinated alcohol category in the US.
The evidence on mixing them yourself is more equivocal than the regulatory action suggests. Peacock and colleagues’ systematic review in Addiction in 2014 synthesized 19 papers and found that people combining alcohol with energy drinks reported more stimulation, less sedation, and more hazardous drinking and risk-taking. The authors added the caveat that gets dropped in most coverage: it was unclear whether the altered intoxication actually drove the extra intake, or whether the people who choose the combination were already higher-risk drinkers.
A 2020 study in Nutrients by Benson and colleagues, surveying 1,369 Australians, shows the problem neatly. Compared across people, those who mixed drank more. Compared within the same individuals across occasions, they drank less alcohol on the nights they mixed. The between-person association is real; the causal story is not.
Reasonable guidance, rather than prohibition
None of the above supports either a ban or a shrug. It supports a short list.
- Count total caffeine against the FDA’s 400 mg. Coffee, tea, chocolate and pre-workout formulas share that budget.
- Read the container size, not the serving size. A can holding two servings is the most common way people exceed what they intended.
- Treat the last caffeine of the day as a sleep decision — an afternoon can is still working at bedtime.
- Skip them entirely for children and adolescents, in line with the pediatric evidence and current FDA guidance.
- Anyone with a diagnosed arrhythmia, long QT syndrome, uncontrolled high blood pressure, or a pregnancy should take the caffeine question to a clinician rather than to a label.
- If the drink is doing a job that sleep would do better, that is worth noticing. Persistent fatigue has causes a blood test can find, which we cover in energy without stimulants.
The sugar-free versions solve a calorie problem and introduce a different set of questions, covered in our piece on non-sugar sweeteners.
Common questions
Is an energy drink worse than a coffee?
Not on caffeine content alone. The 2024 market analysis found a mean of 129 mg per serving against the FDA’s estimate of roughly 130 to 200 mg for a 12-ounce coffee. The differences that matter are container size, how fast a cold carbonated drink gets consumed, and whether sugar comes with it.
Does taurine make caffeine more dangerous?
That was the claim in the earlier version of this article, and it is not supported. The controlled trials compared whole energy drinks against placebo, so they cannot isolate taurine’s contribution. Memorial Sloan Kettering’s summary notes case reports involving energy drinks containing taurine and caffeine, while describing the taurine evidence itself as mixed.
Can energy drinks cause heart problems?
The randomized trials measured small changes in blood pressure and QT interval in healthy adults two hours after consumption. Case reports of serious events exist but cannot establish how often they occur or whether the drink was responsible. People with existing cardiac conditions have the clearest reason to ask a doctor.
What about the deaths reported in the news?
Those figures came from adverse event reports, which record that a product was consumed and something happened. They are a signal-detection tool, not a finding of cause. We repeated them as though they were established, and we should not have.
Where this leaves the can
An occasional energy drink in a healthy adult counting total caffeine is a minor thing. A daily 300 mg habit covering for five hours of sleep is a different thing, and the drink is the symptom. The clearest lines the evidence draws are around adolescents, mixing with alcohol, and anyone with a cardiac condition.
This blog previously used the energy drink safety debate to sell a caffeine-free shot, describing it as completely safe and claiming it produced energy at a cellular level. That product is discontinued and the claim was never supported. What we sell now are green superfood powders, and the case for them is nutritional rather than stimulant — you can read it at Greens Plus.
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