Energy drink or coffee: same caffeine, different label

An energy drink is a coffee that's started a band

Is an energy drink the same as a coffee? Where it matters, almost: the thing that actually does something in both is caffeine.

Coffee walks on stage alone. The can comes with a band. And the question is what the band is playing.

The answer comes with an "almost", and the almost turns out to be the most interesting part.

Five names on the poster, and only one of them sings

Taurine, guarana, B vitamins, glucuronolactone. They sound like they wear lab coats, and on their own they have an overwhelming lack of evidence behind them.

The vitamins and the glucuronolactone turn up for the band photo with their guitars unplugged. Taurine, at best, tunes things up a little in short sports tests.

Guarana is a plant whose star ingredient is caffeine. In the head it does what you'd expect: you press a button a touch faster without getting any more right.

A solo act with scenery. The odd thing is that, with the same caffeine, the can doesn't sound quite like the soloist.

An energy drink can on a wooden surface, lit against a dark background. — Taurine gets its own line on the can. The one doing the singing is caffeine. Photo: Marcel Strauß (Unsplash).

With a band behind it, the soloist sounds a touch louder

With the same caffeine inside, the can keeps blood pressure higher for longer. And one section of the ECG trace, which plain caffeine shortens slightly, stays where it was. Nobody knows which member of the band turns the volume up, and it was quite a gig: eighteen people and almost a litre in one go.

In healthy people drinking normal amounts, the effect is small. The top blood pressure number goes up by almost five millimetres of mercury for a couple of hours, and there's no sign of the pounding heart people swear they can feel. With close to a litre in one sitting, some people do get palpitations, and in some of them that section of the ECG gets stretched.

An average doesn't fit everyone. In long QT syndrome, an inherited fault in the heart's electrical system, the average didn't move. But in three of the twenty-four patients, the can stretched that section to a point the researchers consider dangerous. They advise caution, and nobody has studied what happens with more.

The best-measured part comes once the can is already in the yellow recycling bin.

The gig carries on after you've gone to bed

Caffeine doesn't leave when the can is empty. It leaves in halves: the half-life is how long it takes the body to get rid of half of it. Like packing down a stage one cable at a time.

The packing down is done by the liver, with a single family of enzymes, CYP1A2, which handles 95% of the caffeine. One sound engineer for the whole tour. The job is so completely theirs that hospitals use caffeine to test how well a liver is working. And coffee doesn't shift the markers of liver damage: the legend that it punishes your liver has it backwards.

And the engineer doesn't work the same way in everyone. The gene that makes that enzyme comes in several versions. That's why "coffee does nothing to me" and "one cup at five and I'm awake for the sunrise" can both be true.

While it's still in you, it cuts about three-quarters of an hour of sleep, and not from just anywhere. Deep sleep drops by just over eleven minutes while light sleep goes up. It pockets the banknotes and leaves you the small change.

And you don't have to drink it at night. Six hours before bed, it's still spoiling your sleep, and the real safety margin is longer than people think. Pre-workout powders, the most concentrated form, need the most hours of all.

The circle closes by itself: you sleep too little, you open a can to get through the afternoon, and that can trims the next night. The band plays to cover up how tired it is from its own gig.

The liquid itself can be measured with a strip of paper.

The stage is acidic, and enamel doesn't come with spares

A supermarket energy drink has the pH of a mild vinegar. The ones sold in Spain average around 3.3, already in the range that erodes tooth enamel. Enamel is the hardest thing the body makes, and it doesn't grow back. A bunker with no maintenance crew.

More cans go hand in hand with more acid wear, though the studies behind that are weak, and on tooth decay the data contradict each other. One of the habits that turns up most often next to worn enamel is the acidic last sip before bed: the eleven o'clock encore, with nobody left to clap.

Several plaster dental models with teeth and gums in a dental lab display case. — Enamel is the hardest thing the body makes, and there are no spares. Photo: Quang Tri Nguyen (Unsplash).

The warning on the can was written by the law, not by marketing

There's one line on the can that looks nothing like the rest of the poster: "High caffeine content. Not recommended for children or pregnant or breast-feeding women." It's a legal requirement across the EU, and it's hard not to picture the meeting where it was drafted.

"Drinks with a lot of caffeine: compulsory warning."

"What about coffee?"

"It's called coffee. Anyone who buys it knows what they're buying."

"And if the caffeine comes from a plant with a jungle-sounding name, and it gets its own lettering on the poster?"

"It counts just the same, from whatever source. Even in a wig."

So that's how it ended up. Coffee and tea are let off if their name already tells you what they are, just as a knife doesn't come with a sticker saying it cuts.

Why children? Because for children and teenagers there isn't enough data to set a safe amount of caffeine. It isn't that the limit is low. It's that there's no limit to give.

Mixing them with alcohol is a separate matter, and there is no joke here. It has not been confirmed that the can masks drunkenness. What does appear is that people who mix them drink in riskier ways, although it is not clear that the can is the cause. In the official Spanish survey of pupils aged twelve and thirteen, one in ten had done it in the previous month. Nine in ten had not.

Since March 2026, in Galicia (north-west Spain), they may not be sold to minors or share a shelf with soft drinks. It's the same law that covers alcohol and tobacco. Over there, the band plays a different venue.

So the poster reads: five names, one soloist and a single line that never went through marketing.

What we do with this in class

Over the next few days your fridge may be inspected: someone takes the drinks out one by one, hunts for the word guarana in the small print and puts them all back without opening a single one.

The Six O'Clock Coffee. The first week opens with Carla, fourteen: two coffees, a can before training, and then she's wide awake at two in the morning. In the Caffeine Half-Life Clock they rebuild her day in six glasses of coloured water, each dose poured on top of what was left of the one before. In the Blood Sugar Rollercoaster they draw her morning energy curve and fix it to the paper with a piece of wool.

The second week opens the can. In pH Shock they dip indicator strips into an energy drink, a cola, a juice and water, then put them in order from most acidic to least. It's the same measurement that was done on sixty-seven drinks from the Spanish market, only with four glasses. Then they read labels, hunting for guarana. And before touching anything, each team bets on a theory: the can is a cocktail, the can is a fizzy coffee, or if it's sold everywhere it must be safe. The third one is knocked down by the can itself, which has the warning printed on it.

It all happens in English, with real cans and labels on the table, and the heavy lifting is in the conditional. They have to hold up a whole prediction (if you drink this, that will happen) in front of a team that has bet on the opposite, and then correct it out loud when the pH strip says something else.

Behind both weeks is Marco Sánchez Martín, a sixth-year medical student, working with small groups. The rest of the programme is on the after-school programme page.

If you have a teenager at home

At this age it isn't a theoretical question. According to the official survey, more than a third of pupils aged twelve and thirteen across Spain had had an energy drink in the previous month. Among fourteen- to eighteen-year-olds, on the other hand, consumption peaked in 2023, and in 2025 it fell to its lowest level since records began. And the only thing that shows up in the big pooled studies and depends on home has nothing to do with cans: a bedtime set at home goes hand in hand with more sleep. The rest of the week fits on one label and one sobremesa, the long chat at the table after a meal.

A good way in is a question with a colour for an answer: what colour did the strip turn in the energy drink? Behind the colour comes the whole experiment.

Three challenges for this week:

The warning hunt. Each of you writes down how many products in the house you think have a caffeine warning printed on them. Then go through the fridge and the cupboards, label by label, and whoever gets closest wins. The bonus question is worth double: why doesn't the packet of coffee have one? They know that one.
The table survey. At the next meal with more people round the table, ask everyone the same question: does an afternoon coffee keep you awake? Beforehand, each of you bets on how many will say yes. At the end, they explain why the "coffee does nothing to me" people and the "I don't sleep a wink" people are both right. If they don't mention the liver, it doesn't count.
The honest can. Pick any package in the house with a slogan on the front. They have five minutes to rewrite that front in English, keeping only what really does something, and then read it to you like a radio advert. You play the inspector: every line they can't justify to you is a point for you. The honest version stays on the fridge until Sunday.

If tomorrow you had to write the small print on a can, what line would you put first?

The answer may turn out to be the line that was already there, the warning, in different words and with a lot more conviction. That's what happens when someone works out for themselves which member of the band is really playing: the poster never reads the same again.

Sources

McLellan TM, Lieberman HR. "Do energy drinks contain active components other than caffeine?". Nutrition Reviews 70(12), 730–744 (2012). Review of 32 studies.
Deng H, Wang L, Liu P, Bin Naharudin MN, Fan X. "Caffeine and taurine: a systematic review and network meta-analysis of their individual and combined effects on physical capacity, cognitive function, and physiological markers". Journal of the International Society of Sports Nutrition 22(1), 2566371 (2025). Network meta-analysis of 12 studies.
Hack B, Penna EM, Talik T, Chandrashekhar R, Millard-Stafford M. "Effect of Guarana (Paullinia cupana) on Cognitive Performance: A Systematic Review and Meta-Analysis". Nutrients 15(2), 434 (2023). Eight placebo-controlled studies, 328 participants.
National Institute of Diabetes and Digestive and Kidney Diseases (NIH). "Guarana". LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Bethesda (2023).
Fletcher EA, Lacey CS, Aaron M, Kolasa M, Occiano A, Shah SA. "Randomized Controlled Trial of High-Volume Energy Drink Versus Caffeine Consumption on ECG and Hemodynamic Parameters". Journal of the American Heart Association 6(5), e004448 (2017). Randomised, double-blind crossover trial; 18 young adults.
Gualberto PIB, Benvindo VV, Waclawovsky G, Deresz LF. "Acute effects of energy drink consumption on cardiovascular parameters in healthy adults: a systematic review and meta-analysis of randomized clinical trials". Nutrition Reviews 82(8), 1028–1045 (2024). Meta-analysis of 17 randomised trials.
Ehlers A, Marakis G, Lampen A, Hirsch-Ernst KI. "Risk assessment of energy drinks with focus on cardiovascular parameters and energy drink consumption in Europe". Food and Chemical Toxicology 130, 109–121 (2019). German Federal Institute for Risk Assessment.
Gray B, Ingles J, Medi C, Driscoll T, Semsarian C. "Cardiovascular Effects of Energy Drinks in Familial Long QT Syndrome: A Randomized Cross-Over Study". International Journal of Cardiology 231, 150–154 (2017). Crossover trial, 24 patients with long QT syndrome.
Grzegorzewski J, Bartsch F, Köller A, König M. "Pharmacokinetics of Caffeine: A Systematic Analysis of Reported Data for Application in Metabolic Phenotyping and Liver Function Testing". Frontiers in Pharmacology 12, 752826 (2022). Systematic analysis of data from 141 publications.
Nehlig A. "Interindividual Differences in Caffeine Metabolism and Factors Driving Caffeine Consumption". Pharmacological Reviews 70(2), 384–411 (2018). Narrative review.
Linden-Torres E, Zambrano-Galván G, Sahebkar A, Ríos-Mier M, Simental-Mendía LE. "Coffee consumption has no effect on circulating markers of liver function but increases adiponectin concentrations: A systematic review and meta-analysis of randomized controlled trials". Nutrition Research 106, 24–34 (2022). Meta-analysis of 14 randomised trials and 897 participants.
Gardiner C, Weakley J, Burke LM, Roach GD, Sargent C, Maniar N, Townshend A, Halson SL. "The effect of caffeine on subsequent sleep: A systematic review and meta-analysis". Sleep Medicine Reviews 69, 101764 (2023). Meta-analysis of 24 studies.
Drake C, Roehrs T, Shambroom J, Roth T. "Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed". Journal of Clinical Sleep Medicine 9(11), 1195–1200 (2013). Placebo-controlled trial, carried out in the participants' own homes.
Martínez LM, Lietz LL, Tarín CC, García CB, Tormos JIA, Miralles EG. "Analysis of the pH levels in energy and pre-workout beverages and frequency of consumption: a cross-sectional study". BMC Oral Health 24(1), 1082 (2024). Sixty-seven drinks from the Spanish market measured.
Luo BW, Liang NL, Sun IG, Chu CH, Duangthip D. "Association Between Consumption of Energy and Sports Drinks with Oral Health: A Systematic Review". Dentistry Journal 14(6), 359 (2026). Ten studies, 5,805 participants.
Chan AS, Tran TTK, Hsu YH, Liu SYS, Kroon J. "A systematic review of dietary acids and habits on dental erosion in adolescents". International Journal of Paediatric Dentistry 30(6), 713–733 (2020). Adolescents aged 10 to 19.
Regulation (EU) No 1169/2011 of the European Parliament and of the Council of 25 October 2011 on the provision of food information to consumers. Official Journal of the European Union L 304, 18–63 (2011), Annex III, point 4.
European Food Safety Authority (EFSA), NDA Panel. "Scientific Opinion on the safety of caffeine". EFSA Journal 13(5), 4102 (2015).
Observatorio Español de las Drogas y las Adicciones (Spanish drugs observatory). Estudio piloto ESTUDES 2023 12 y 13 años. Encuesta piloto sobre uso de drogas y adicciones en estudiantes de enseñanzas secundarias de 12 y 13 años de 1º y 2º ESO en España. Madrid: Ministerio de Sanidad, DGPNSD (2023). 8,023 pupils.
Observatorio Español de las Drogas y las Adicciones. ESTUDES 2025: bebidas energéticas. Madrid: Ministerio de Sanidad, DGPNSD (2025).
Peacock A, Pennay A, Droste N, Bruno R, Lubman DI. "'High' risk? A systematic review of the acute outcomes of mixing alcohol with energy drinks". Addiction 109(10), 1612–1633 (2014). Review of 19 studies.
Benson S, Verster JC, Alford C, Scholey A. "Effects of mixing alcohol with caffeinated beverages on subjective intoxication: a systematic review and meta-analysis". Neuroscience & Biobehavioral Reviews 47, 16–21 (2014). Meta-analysis of 9 experimental studies.
Ley 6/2025, de 23 de diciembre, de protección de la salud de las personas menores y prevención de las conductas adictivas (Galicia). Diario Oficial de Galicia no. 3 (7 January 2026); BOE (Spain's official gazette) no. 40 (14 February 2026).
Bartel KA, Gradisar M, Williamson P. "Protective and risk factors for adolescent sleep: a meta-analytic review". Sleep Medicine Reviews 21, 72–85 (2015). Forty-one studies, 85,561 adolescents.