Energy drinks and energy shots are food supplements that typically contain sugar, artificial sweeteners, and a stimulant like caffeine, taurine, or guarana (which contains caffeine). However, they usually also contain a large array of other substances including glucuronolactone, carnitine, choline, electrolytes (sodium, potassium, magnesium, etc.), and vitamins — vitamin A, vitamin C, vitamin D, and vitamins B3, B6, and B12. Consequently, the composition of different energy drinks and shots is highly variable. For example, the caffeine content of an energy drink can range from 45 to 400 milligrams (174±81 milligrams on average),^[5][6] while the sugar content can range from 1 to 63 grams (19.9±18.2 grams on average).^[5][6]

Energy drinks and shots are often known by their brand names — 5-hour Energy, Rockstar Energy, Red Bull, etc. — and are marketed to improve focus, increase energy, and reduce feelings of fatigue. Energy drink consumption is popular worldwide,^{[7][8][9][10][11]} especially in teenagers and young adults,^{[12][13][14][15]} and their market is huge: in 2021, the global market for energy drinks was valued at $86 billion.^[16]

Manufacturers focus their advertisement campaigns at people involved in extreme sports, esports, and people engaged in cognitively demanding work, and use brand ambassadors and sponsored athletes to “influence” engagement.^[17] However, in the face of their popularity and claimed effects, several scientists and organizations have raised awareness of the potential adverse health effects of energy drinks and shots, claiming that they’re a public health concern.^[18][19][20]

Some studies show that energy drinks can reduce feelings of sleepiness and fatigue,^[21][22][23] increase feelings of alertness,^[24][25] and improve some aspects of cognitive function, including mood,^[24] attention,^[26][27][24] memory,^[28][26][24] and reaction time.^{[5][29][30][25]} Energy drinks have also been shown to reduce ratings of perceived exertion (RPE) during exercise and enhance aerobic and anaerobic exercise performance.^{[5][31][32][33]} However, existing randomized controlled trials examining the effects of energy drinks are few in number, include small numbers of participants, and often lack a control group for each ingredient. Furthermore, existing trials have large variability in the types of participants, testing modalities, and product ingredients. Therefore, further high-quality research is needed to make firm conclusions.

It is also important to note that caffeine is the primary ingredient — and typically the sole stimulant — added to energy drinks.^[5][6] Consequently, it is very likely that caffeine is responsible for the above-described effects of energy drinks because ample evidence shows that all of these effects are also caused by caffeine in isolation.

Studies examining the effects of energy drinks have highly variable study designs, and long-term randomized controlled trials are lacking.^[34] Consequently, further high-quality studies are needed to fully understand the short- and long-term drawbacks of energy drinks and shots. That said, several papers reviewing the evidence from observational studies have highlighted public health concerns about energy drinks, which are due to their numerous side effects and their potential adverse health effects.^{[18][19][35][20]}

Common side effects of energy drinks include headache, shortness of breath, jitteriness/restlessness, gastrointestinal upset, and sleep problems (e.g., insomnia).^{[36][37][38][38]} Furthermore, observational studies indicate that frequent energy drink consumers are more likely to consume other caffeine-containing beverages,^[39] and are also more likely to engage in unhealthy behaviors, such as alcohol, drug use, and smoking, and more likely to make less-healthful dietary choices such as sugar-sweetened beverages and junk foods.^{[39][40][41][42][43][44]}

Consumption of energy drinks and shots is also associated with increased stress, anxiety, and depression-related symptoms.^[45][5][38] However, such health risks are often derived from observational studies involving cross-sectional study designs and correlation analyses, which makes it difficult to be confident about causality. Furthermore, “reverse causation” is also possible — i.e., people with conditions like anxiety or depression might be more likely to consume energy drinks to cope with symptoms. That said, one 2-year observational study found that male participants who went from being a non-energy drink user to an energy drink user had an increase in stress, anxiety, and depression-related symptoms over the course of the study, even after controlling for known confounders.^[46] Further studies are needed to make firm conclusions concerning the association between energy drink use and mental health.

Consuming an energy drink can acutely raise heart rate and blood pressure at rest^[47][48][49] and during exercise,^[50][47] and delay their recovery following exercise.^[50][47] Energy drinks can also disturb electrical activity in the heart: electrocardiogram (ECG) readings show a prolonged QRS complex (the time it takes for heart muscles to contract) and lengthened QTc intervals (the time it takes for heart muscles to relax after they start to contract).^[47] The long-term effects of such outcomes are currently unclear, but people with heart conditions should exercise caution when consuming energy drinks and consult their doctor if they are unsure.

There have been several case reports of adverse cardiovascular events occurring following the consumption of energy drinks and shots.^{[51][52][53][54][55][56][57]} However, these have largely occurred when energy drinks or shots were consumed either in excess or in combination with other substances with potential adverse effects, such as alcohol and drugs.^[58] While the population-level incidence of an adverse event is low^[59], it’s important to note that, particularly for members of certain groups (children, teenagers, people with underlying heart conditions), dramatically exceeding one's recommended daily caffeine intake limit, whether by energy drinks alone or in combination with other caffeine-containing food and drink, carries risks to one's health.^[60][61]

It is difficult to identify the component of energy drinks responsible for the above-described effects, because most studies do not include the multiple control groups that would be needed to compare the energy drink or shot to each of its listed ingredients. However, caffeine is a likely candidate, because its benefits — improved cognitive function and exercise performance, etc. — and adverse effects — elevated heart rate and blood pressure, sleep disturbance, headaches, etc. — are almost identical to those caused by energy drinks. For more information, please read our article: How does caffeine work?.

In addition to caffeine, energy drinks also typically contain sugar, which might contribute to the exercise-performance-enhancing effect of energy drinks and shots that has been documented in some studies.^[5] However, the sugar content of energy drinks is highly variable (1–63 grams; 19.9±18.2 grams on average),^[5][6] and further studies are needed to understand the contribution of energy drinks’ sugar content to the claimed effects.

Many other ingredients are added to energy drinks and shots: taurine, glucuronolactone, carnitine, choline, electrolytes, vitamin A, vitamin C, vitamin D, and vitamins B3 (niacin), B6, and B12. The known effects of these ingredients do not align with the claimed benefits of energy drinks and shots. That said, some studies have found greater disturbances in blood pressure and in the heart’s electrical activity after consumption of an energy drink than after a drink containing identical amounts of caffeine, but lacking the energy drink’s other ingredients.^[62][63] This suggests that some energy drink ingredients besides caffeine may also have detrimental effects. However, the problem is that most studies simply compare an energy drink to water, rather than having a control group for each ingredient (e.g., energy drink vs. water, vs. water+caffeine, vs. water+taurine, vs. water+sugar, etc.). Therefore, the additional ingredients in energy drinks have not been studied in adequate detail to fully understand their benefits or risks, or the lack thereof.^[18] Consequently, further high-quality research is necessary to fully understand how energy drinks cause their benefits and drawbacks.