In this randomized crossover study, we compared the effects of an energy drink and coffee with **identical caffeine content** on cardiac repolarization dynamics in healthy volunteers. The consumption of **energy drinks resulted in an increase in PRD levels (3.64 vs. 5.85 deg²; p < 0.001)**, whereas **coffee consumption did not lead to an increase in PRD levels**. The authors conclude that ‘the increase in PRD levels after energy drink consumption may indicate a **pro-arrhythmic potential of energy drinks beyond the effect of caffeine alone**, possibly related to other ingredients such as taurine or the pattern of intake.’

In this randomized, double‐blind, crossover study, healthy volunteers consumed either 32 oz of a commercially available energy drink or a control drink containing the **same amount of caffeine (320 mg)**. The authors report: "The change in corrected QT interval from baseline in the energy drink arm was significantly higher than the caffeine arm at 2 hours (0.44±18.4 ms versus −10.4±14.8 ms, respectively; P=0.02)." They further state that "while both the energy drink and caffeine arms raised systolic BP in a similar fashion initially, the systolic BP was significantly higher at 6 hours when compared with the caffeine arm (4.72±4.67 mm Hg versus 0.83±6.09 mm Hg, respectively; P=0.01)." The conclusion notes: "The corrected QT interval and systolic BP were significantly higher post high-volume energy drink consumption when compared with caffeine alone."

This American Heart Association journal article describes a double‐blind, randomized, crossover trial where participants consumed **32 oz of an energy drink or a caffeine‐matched control drink (320 mg)**. The authors report: "A significant difference in the baseline‐adjusted QTc interval was evident 2 hours after energy drink consumption when compared with caffeine (0.44±18.4 ms versus −10.4±14.8 ms, respectively; P=0.02)." They also note that "while both the energy drink and caffeine arms raised systolic BP in a similar fashion initially, the systolic BP was significantly higher at 6 hours when compared with the caffeine arm (4.72±4.67 mm Hg versus 0.83±6.09 mm Hg, respectively; P=0.01)." The authors conclude: "The corrected QT interval and systolic BP were significantly higher post high‐volume energy drink consumption when compared with caffeine alone."

In this randomized, double‐blind, placebo‐controlled, crossover trial, 34 healthy volunteers consumed two different 32‐oz caffeinated energy drinks (drinks A and B) and a caffeine‐free placebo on separate days. The authors state: "The maximum change from baseline in Bazett's corrected QT interval for drinks A, B, and placebo were +17.9±13.9, +19.6±15.8, and +11.9±11.1 ms, respectively (P=0.005 for ANOVA)." They report that peripheral and central systolic and diastolic blood pressure were "statistically significantly different compared with placebo" and that the maximum SBP changes with drink A and B were significantly higher than with placebo. In the discussion, they reference a prior caffeine‐controlled trial: "In a small (n=18) randomized, caffeine‐controlled clinical trial, 32 oz of an energy drink resulted in a significantly higher QTc at 2 hours when compared with the caffeinated control (+0.4±18.4 ms versus −10.4±14.8 ms, respectively; P=0.02)."

The PubMed abstract for this randomized, double‐blind, placebo‐controlled, crossover study reports that healthy adults consumed 32 oz of 2 different caffeinated energy drinks or placebo. It states: "The maximum change from baseline in QTcB was 17.9±13.9 ms for energy drink A, 19.6±15.8 ms for energy drink B, and 11.9±11.1 ms for placebo (P=0.005)." The authors note that both energy drinks led to statistically significant increases in peripheral and central blood pressure compared with placebo. In the background and discussion, they reference prior caffeine‐controlled work, explaining that an earlier trial found that 32 oz of an energy drink produced a significantly higher QTc at 2 hours than a caffeinated control drink containing the same amount of caffeine.

This review summarizes clinical and experimental data on energy drinks. It reports that **energy drink intake has been associated with increased blood pressure, prolonged QTc interval, and cases of arrhythmia, myocardial infarction, and sudden cardiac death**, often in young individuals. The authors emphasize that ‘**adverse cardiovascular effects of energy drinks appear to exceed those of caffeine alone**, suggesting a role of other components and the pattern of consumption (rapid ingestion of large doses).’ The review contrasts this with evidence that **habitual coffee consumption is generally not associated with increased cardiovascular risk and may even be protective** at moderate intakes.

This narrative review notes that caffeine is the main active ingredient in energy drinks, stating: "The major constituent in most energy drinks is caffeine. They usually contain 80–150 mg of caffeine per 8 ounces, which is equivalent to 5 ounces of coffee or 2 cans of cola." It emphasizes that negative events are typically linked to the *combination* of caffeine with other ingredients: "The adverse health effects associated with energy drink consumption are mostly related to their caffeine content in combination with other stimulants, such as guarana and taurine, as well as high sugar content." The authors contrast this with coffee, mentioning that coffee consumption has been associated in other literature with reduced risk of several chronic diseases, whereas energy drink literature highlights cardiovascular and metabolic concerns, especially in youth.

This editorial reviews controlled studies of energy drinks and cardiac electrophysiology. It summarizes a double‐blind crossover trial in which healthy volunteers consumed 2 different caffeinated energy drinks or a caffeine‐free placebo: "Both energy drinks produced an average maximal increase in heart rate–corrected QT interval (QTc) of 18 to 20 ms that persisted up to 4 hours after consumption. In contrast, the placebo drink was followed by only a small transient increase in QTc." The article notes that "caffeinated energy drinks significantly prolong the QTc interval and raise brachial and central blood pressure post–acute exposure." It also emphasizes: "The electrocardiographic effects of caffeine, the main ingredient in energy drinks, have been extensively studied; there is **no convincing evidence that caffeine alone causes QTc prolongation**."

In this randomized, double‐blind, crossover study, 27 healthy young adults consumed 32 oz of a commercially available energy drink or placebo. The abstract reports that energy drink consumption "resulted in a modest increase in QTc interval" and states that the QTc interval was "transiently higher (6 ms) at 2 hours after 32-oz energy drink consumption when compared with placebo (+3.4±10.7 and −3.2±11.8 ms, respectively; P=0.030)." Systolic blood pressure was also increased following energy drink intake compared with placebo. The authors conclude that acute consumption of a large volume of energy drink was associated with "a mild but significant increase in QTc and blood pressure" in healthy young adults.

This review summarizes reported adverse health events associated with energy drink consumption, many involving high caffeine doses often in combination with other substances. It notes that while caffeine is the primary psychoactive ingredient, "the potential contribution of other ED constituents (e.g., taurine, guarana, sugar) to ED-related adverse events remains unclear" and that some studies suggest possible synergistic cardiovascular effects. The authors contrast EDs with other caffeine sources: "Coffee and tea, which also contain caffeine, have generally been associated with neutral or beneficial health effects in observational studies, whereas ED consumption has more frequently been linked with acute adverse events, particularly among children and adolescents." They stress that comparisons are complicated by differences in patterns of use (rapid ingestion, mixing with alcohol) and by co-ingredients in EDs.

This systematic review and meta-analysis of randomized and non-randomized studies evaluated acute cardiovascular responses to energy drinks in healthy adults. It found that EDs (typically containing 80–320 mg caffeine per serving plus taurine and sugar) were associated with significant increases in systolic and diastolic blood pressure and QTc interval compared with placebo or control drinks. The authors state: "The observed changes in blood pressure and QTc were modest but statistically significant," and they note that "some evidence suggests that these effects may not be fully explained by caffeine alone, raising the possibility that other ingredients or their combination with caffeine could contribute." They highlight that similar caffeine doses from coffee or tea are generally associated with smaller or no QTc effects in the literature, although direct head-to-head trials with equivalent caffeine doses are limited.

The UC Davis nutrition sheet explains that energy drinks are non-alcoholic beverages that "often include ingredients like caffeine, taurine, B-vitamins and herbal supplements." It notes that, although energy drinks may provide alertness effects similar to caffeine, "energy drinks have more ingredients than just caffeine and it is still unclear if these effects are from the caffeine, the herbal ingredients, or the combination of them." It emphasizes that adults who consume energy drinks "should do so with caution" and that drinking more than one per day, especially combined with other caffeinated products like coffee, can lead to excessive caffeine intake. The sheet also notes that energy drinks often contain added sugar and that other added ingredients such as guarana (which itself contains caffeine) "may substantially increase the effects" of an energy drink.

Mayo Clinic notes that while taurine in energy drinks "may not cause a problem, the other ingredients in these beverages could." It states that energy drinks may include "caffeine, sugar and other ingredients such as herbal extracts" and that "because of that, the safety of these drinks is less clear." It adds that adults without underlying conditions can often tolerate energy drinks, but in some people they "cause dehydration and problems falling asleep" and can make a person "feel nervous and tense," with most of these issues appearing to be from the caffeine. The article also notes that, due to caffeine content, "children or teens should not drink energy drinks" according to the American Academy of Pediatrics.

This brief review in a major medical journal notes that energy drinks typically contain caffeine, sugar, and other substances such as taurine, guarana, and B vitamins. It states that adverse events (e.g., palpitations, insomnia, nervousness, and, rarely, arrhythmias or seizures) have been reported "particularly when EDs are consumed in large quantities or mixed with alcohol." The authors compare this with coffee: "Although coffee and tea also provide substantial amounts of caffeine, their consumption has generally been associated with neutral or beneficial effects on cardiovascular and all-cause mortality in large cohort studies." They also emphasize that EDs are often consumed rapidly and in large-volume servings, which may alter the hemodynamic impact compared with sipping coffee.

This review from a peer‑reviewed journal discusses combined taurine and caffeine exposure through energy drinks, particularly in adolescents. It reports that energy drinks typically contain caffeine together with taurine and other ingredients, and summarizes evidence that consumption of energy drinks is associated with a variety of adverse outcomes, including sleep disturbances, anxiety, and risk‑taking behavior. It also notes that "those who consume taurine and caffeine may be at risk of higher alcohol consumption compared with those who do not," highlighting concern that the combination and context of energy drink use can exacerbate health risks beyond caffeine alone.

An article in the Cleveland Clinic Journal of Medicine explains that taurine is widely used in energy drinks together with caffeine. It notes that taurine supplementation has been proposed to have beneficial effects in conditions such as epilepsy, heart failure, cystic fibrosis, and diabetes, but also warns about neuroendocrine effects of high taurine intake in the context of energy drinks. The article discusses concerns that, when combined with caffeine and other stimulants in energy drinks, taurine could influence the hypothalamic‑pituitary‑adrenal axis and cardiovascular system, suggesting that the mixture of ingredients may have different physiological effects than caffeine alone.

An American Heart Association scientific statement in Circulation describes energy drinks as beverages that typically contain caffeine along with other ingredients such as taurine, B vitamins, herbal extracts, and sugar. It reviews reports of cardiovascular events like arrhythmias, elevated blood pressure, and, in rare cases, sudden cardiac death associated with energy drink consumption, particularly in young people. The paper emphasizes that these effects may be related to "the high caffeine content in combination with other stimulants" and that the overall safety profile differs from that of traditional caffeinated beverages such as coffee, where caffeine is usually consumed without these additional compounds and large sugar loads.

This clinical trial compared the acute cardiovascular effects of a commercially available energy drink with a drink containing equivalent caffeine but without the other energy drink ingredients. In healthy volunteers, the energy drink produced a significantly greater increase in systolic blood pressure and a prolongation of the QTc interval than the control drink with the same caffeine dose. The authors concluded that ingredients in energy drinks "other than caffeine" contribute to their observed cardiovascular effects, suggesting that consuming caffeine within an energy drink formulation can have different, potentially more adverse, acute effects than consuming the same amount of caffeine alone.

A randomized trial published in JAMA examined the effects of high‑volume energy drink consumption compared with a control drink containing the same amount of caffeine but no other energy drink ingredients. Participants who consumed the energy drink showed statistically significant increases in systolic blood pressure and a prolongation of the QTc interval compared with the caffeine‑only control. The authors stated that these findings indicate that "ingredients other than caffeine" in energy drinks can contribute to observed cardiovascular changes, implying that the health impact of caffeine may be more concerning when delivered via energy drinks than when taken in isolation.

Reporting on the randomized, double‐blind trial in the *Journal of the American Heart Association*, ScienceDaily explains that participants drank either "32 ounces of a commercially available energy drink" or "a control drink with the same amount of caffeine -- 320 milligrams (mg)." The summary notes: "Two hours after drinking 32 ounces of a commercially available energy drink, the heart's electrical activity was abnormal compared to drinking a caffeine-matched control drink." It states that, compared with the caffeine group, "those in the energy drink group had a corrected QT interval 10-milliseconds higher at 2 hours." The article also describes that while systolic blood pressure increased in both groups, "blood pressure normalized faster after caffeine" whereas those who consumed the energy drink "still had a mildly elevated blood pressure after six hours," suggesting that "ingredients other than caffeine may have some blood pressure altering effects."

The article notes that experts have ‘cautioned that, despite their popularity, caffeine‑based products and other types of energy‑boosting supplements could have adverse effects, especially on cardiovascular health.’ It cites a position statement from the European Association of Preventive Cardiology that a formulation containing caffeine, taurine, and glucuronolactone **‘may increase arterial blood pressure, act as a platelet aggregation enhancing factor and compromise endothelial function in healthy individuals.’** The authors highlight ‘a range of cardiovascular side effects linked to consumption of energy drinks, including coronary disease, heart failure, cardiac arrhythmias, ventricular tachycardia, and aortic dissection.’ In contrast, they note that observational studies suggest that **caffeine as found in commonly consumed beverages like coffee does not have a meaningful negative effect on heart rhythm disturbances and may even protect against some common arrhythmias.**

Harvard’s public health nutrition resource explains that energy drinks usually contain caffeine plus sugar and other ingredients like taurine, guarana, and B vitamins. It notes: "Most energy drinks contain between 70 and 240 mg of caffeine in a 16-ounce serving," and that many also have "large amounts of added sugar" comparable to soft drinks. The page contrasts EDs with coffee and tea: "Coffee and tea, despite their caffeine content, have been associated in many studies with health benefits, including lower risk of type 2 diabetes and cardiovascular disease." In discussing health risks, it states that EDs have been linked to increased emergency department visits, particularly among adolescents and young adults, and that some adverse cardiovascular and sleep effects "may be related to the rapid consumption of large volumes and the presence of other stimulants in addition to caffeine."

A brief review in The BMJ summarizes the health concerns associated with energy drink consumption. It notes that energy drinks typically contain high levels of caffeine along with sugar, taurine, and other additives, and that consumption has been linked to insomnia, nervousness, heart palpitations, and in some cases emergency department visits. The review contrasts energy drinks with other caffeinated beverages, explaining that the combination of high caffeine doses, high sugar content, and other stimulants in energy drinks raises different safety concerns than coffee or tea, even when total caffeine amounts are similar.

This narrative review concludes that ‘**energy drinks cause varying degrees of adverse cardiovascular effects when consumed in specific dosages**. While the highest levels of consumption led to arrhythmias, syncope and death, lower levels led to increased QTc interval and increased blood pressure.’ Importantly, the authors state that ‘**the effects of energy drinks were deemed greater than those caused by caffeine alone**.’ When analyzing ingredients, ‘caffeine, sugar, and guarana were found likely responsible for the adverse effects of energy drinks’ while taurine’s effect was less convincing. The review also points out that the caffeine content of many energy drinks ‘**are not higher than the amounts of caffeine in many coffees** such as those sold by Starbucks and Dunkin Donuts, suggesting that **non‑caffeine components or consumption patterns contribute to the differential risk.**’

This ACC release describes a study on chronic high caffeine intake from various sources, including coffee, soda, and energy drinks. It reports that **drinking over 400 mg of caffeine per day on most days could increase susceptibility to cardiovascular disease**, with chronic intake at this level ‘shown to significantly impact the autonomic nervous system, raising the heart rate and blood pressure over time.’ It notes that 400 mg corresponds to ‘about four cups of coffee, 10 cans of soda or **two energy drinks**.’ The study does not single out energy drinks as more harmful than coffee at equivalent caffeine doses but underscores that **high total caffeine load, regardless of source, is associated with elevated heart rate and blood pressure.**

Mayo Clinic cardiology experts note that **energy drinks, especially when consumed rapidly or in large quantities, may trigger abnormal heart rhythms and increases in blood pressure**. They highlight that while moderate caffeine intake from coffee is generally considered safe for most healthy adults, ‘**energy drinks contain not only caffeine but also other stimulants and additives**’ and that ‘there have been reports of serious heart rhythm disturbances and even sudden death in people who consumed energy drinks.’ The FAQ advises individuals with heart rhythm problems to be particularly cautious with energy drinks compared with other caffeinated beverages such as coffee.

This article summarizes a randomized crossover clinical trial comparing caffeine exposure from coffee and an energy drink at an equal dose of 160 mg caffeine. It reports that according to the study published in *Clinical Toxicology*, "caffeine exposure was very similar between the five conditions studied" and "would not be expected to result in clinically significant differences in effect." The press release states: "The study suggests that in terms of caffeine absorption and metabolism, coffee and energy drinks are very similar and that rate of consumption and temperature of drink don’t significantly alter caffeine absorption." It also notes that the trial specifically measured blood caffeine concentrations, not clinical endpoints like arrhythmias or blood pressure.

An article from Florida Cancer Specialists explains that taurine is a common ingredient in many energy drinks, added for potential effects on mental performance and fatigue reduction. It notes that taurine itself does not cause cancer, but recent research has suggested complex links between taurine and cancer cell growth, particularly in blood cancers such as leukemia. The article warns that high amounts of taurine, especially when combined with caffeine in energy drinks, have been linked to side effects such as "increased heart rate, high blood pressure, anxiety, and sleep disturbances," and advises people with blood cancers or at higher risk to be cautious with high‑taurine energy drinks.

EFSA’s scientific opinion on caffeine safety states that for healthy adults, single doses of caffeine up to 200 mg and total daily intakes up to 400 mg are generally not associated with safety concerns. The report notes, however, that caffeine exposure from energy drinks can be higher in certain population groups, particularly adolescents and young adults, because they may consume large volumes quickly or in combination with alcohol. It also explains that energy drinks can contain other substances, such as taurine and glucuronolactone, and while these were evaluated separately, the combined effects in typical consumption patterns are a consideration distinct from the effects of caffeine consumed in coffee or tea.

Jefferson cardiologists explain that ‘a cup of coffee contains around **90 mg of caffeine**, while an energy drink may contain anywhere between **100 to 350 mg**,’ and that some cans contain more than one serving. They warn that ‘over the past few years, more and more reports have shown that the consumption of energy drinks… can have **adverse effects on the heart**,’ including QT prolongation and arrhythmias. They contrast this with guidance that the FDA considers up to **400 mg of caffeine a day** generally safe in people without underlying heart disease, and that depending on the condition, ‘your cardiologist may say it’s safe to drink one or two cups of coffee per day.’ The article also notes that **added sugars and high caloric content** in some energy drinks and specialty coffees can contribute to weight gain, diabetes, and long‑term cardiovascular risk.

A registered dietitian at an academic medical center explains that both coffee and energy drinks mainly provide caffeine, but their health profiles differ. On caffeine, she notes: "For most healthy adults, up to 400 milligrams of caffeine a day is safe," regardless of source. However, the article highlights additional components: energy drinks often have "100 to 300 milligrams of caffeine in a single can" plus large amounts of added sugar, and excessive added sugar is "linked to diabetes, heart disease, weight gain and a number of other health problems." By contrast, "coffee is a natural, plant-derived food that contains vitamins, antioxidants and other nutrients" and "another distinct advantage coffee has over energy drinks: Its many health benefits are supported by decades of large observational research studies." The dietitian concludes: "Because coffee is a natural, plant-derived food that contains vitamins, antioxidants and other nutrients, without added sugar, I’d recommend it as the healthier choice over most energy drinks."

This systematic review and meta‑analysis of randomized and observational studies concluded that **energy drink consumption acutely increases systolic and diastolic blood pressure and may prolong the QTc interval**. The authors discuss that these changes ‘**cannot be fully explained by caffeine content alone**,’ given that similar caffeine doses in control beverages or coffee do not consistently produce the same magnitude of blood pressure rise or QTc prolongation. They suggest that **other ingredients (e.g., taurine, glucuronolactone) and the rapid ingestion of large volumes** likely contribute to the observed cardiovascular effects.

This academic thesis reviews multiple clinical studies on energy drinks, including the randomized caffeine‐controlled trial by Fletcher and colleagues. It notes that Fletcher et al. "investigated effects of energy drink versus caffeinated control drink on QT prolongation and blood pressure elevation" and that the study "demonstrated association with QT prolongation and blood pressure elevation after consumption." The thesis states that in a related placebo‐controlled trial, "the maximum baseline-adjusted difference of QTc interval was significantly higher in the energy drink arm than the placebo arm (13.68 ± 12.71 vs 4.20 ± 8.80 ms, respectively, p = 0.007)." It contrasts this with studies of caffeine-containing drinks alone, where "it was shown to shorten QTc interval and no significant difference was seen for systolic blood pressure." Overall, it concludes: "The results of the study demonstrated that both energy drinks significantly prolong QTc interval and raise blood pressure."

This reprint of the *Circulation: Arrhythmia and Electrophysiology* editorial summarizes evidence on energy drinks and QT prolongation. It states: "Caffeinated energy drinks significantly prolong the QTc interval and raise brachial and central blood pressure post–acute exposure." The piece highlights that in controlled trials, energy drinks increased QTc by approximately 18–20 ms and increased blood pressure compared with placebo. It contrasts this with caffeine, noting: "The electrocardiographic effects of caffeine, the main ingredient in energy drinks, have been extensively studied; there is no convincing evidence that caffeine alone causes QTc prolongation."

This patient resource summarizes clinical research on energy drinks in the context of sudden arrhythmic death syndromes. It cites the randomized trial of high-volume energy drink versus caffeine and notes: "Conclusions: The corrected QT interval and systolic BP were significantly higher post high-volume energy drink consumption when compared with caffeine alone." It further states: "Energy drinks significantly prolong the QTc interval and raise blood pressure." For patients with long QT syndrome (LQTS), it reports that caffeinated energy drinks have "significant haemodynamic effects" including an acute increase in blood pressure, and that dangerous QTc prolongation was seen in some LQTS patients, leading to a recommendation for caution in young patients with LQTS consuming energy drinks.

This industry‑affiliated information page cites regulatory and scientific bodies to argue that **moderate caffeine intake (up to 400 mg/day) from coffee or energy drinks is not associated with increased cardiovascular risk in healthy adults**. It states that ‘despite repeated attempts to demonstrate an association between caffeine/coffee and various types of cardiovascular disease, research has led to the conclusion that ingestion of moderate amounts (400 mg caffeine per day) of coffee and other caffeine‑containing beverages is not associated with any increase in cardiovascular risk in real life settings.’ It also claims that ‘**energy drinks typically contain the same amount of caffeine as a cup of home‑brewed filter coffee**’ and that ‘**the moderate intake of caffeine has no adverse impact on the human heart.**’

Experimental studies examining pure caffeine or caffeine in coffee typically report transient increases in blood pressure and sympathetic nervous system activity, but they have not consistently shown clinically meaningful QTc prolongation in healthy adults at usual consumption levels. Observational evidence has generally found that habitual coffee consumption, even up to several cups per day, is not associated with increased arrhythmia risk and may be linked to neutral or lower cardiovascular risk compared with non-consumption, suggesting that caffeine delivered via coffee does not typically produce the degree or pattern of QTc prolongation seen in high-volume energy drink trials.

A commercial overview of taurine in energy drinks notes that most scientific evidence considers taurine itself to be safe up to about 3,000 mg per day, and that typical energy drink servings contain less than this. It argues that "the health issues associated with energy drinks are almost always due to their high sugar and caffeine content" rather than taurine, pointing out that many popular energy drinks contain 40–60 grams of sugar per can and sometimes 300 mg or more of caffeine per serving. The article states that drinking a "high‑sugar, high‑caffeine energy drink every day is not recommended by health experts."