Some studies support the temporary health benefits of ED in improving mental and physical stamina among both adults and adolescents. Several randomized controlled trials among adults have shown an association between components of ED and improved subjective alertness (21), as well as restoration of fatigue (22). Due to its similar structure to adenosine, caffeine can inhibit sleep through its competitive binding to the adenosine receptor (23). Studies have also shown the effect of ED on improved physical activity performance in young-adult athletes (24–27). A recent meta-analysis of acute-effect studies conducted among adults found that ED consumption improved muscle strength and endurance, performance on endurance exercise tests, jumping, and sport-specific actions (28).

In contrast, the vast majority of evidence suggests negative health effects of both short- and long-term ED consumption (Table 1), with most literature proposing these health disadvantages are attributable to high levels of caffeine and sugar while highlighting that more research is needed on the effects of other ED constituents.

Several studies report a consistent association between ED consumption and substance abuse, although the evidence base consists primarily of cross-sectional studies, which does not allow for establishing directionality of the association (29–34). For example, in a nationally representative sample of U.S. middle- and high-school students, significant associations were found between ED frequency and 30-day frequency of use of alcohol, cigarettes, marijuana, or amphetamines (32). This echoes cross-sectional results among adolescent regular consumers (>1 ED/week) in Europe who were more likely to smoke and drink alcohol compared to non-consumers (35). Some studies have additionally found evidence for an association between ED consumption and mental health, including stress, anxiety, depressive symptoms, and suicidal ideation, plan or attempt (33, 36, 37). For example, teenagers in Canada who reported ED consumption more than once a month were nearly three times more likely to report elevated depressive symptoms compared to those who did not report ED consumption (33). A review of ED consumption and mental health among adolescents and adults supported a positive association between chronic ED use and undesirable mental health effects, including stress, anxiety, and depression (37). The authors postulate that this association may be moderated by dysregulated sleep, such that consuming heavily caffeinated ED may result in sleep loss which in turn may contribute to poor functioning and mental health.

Numerous studies have explored the short-term effects of ED on the cardiovascular system, primarily with respect to caffeine and sugar (38–40). For example, a recent randomized crossover study on healthy subjects found that consumption of 355 mL of an ED resulted in increased systolic and diastolic blood pressure, heart rate, and cardiac output (39). A 2016 meta-analysis of 15 studies similarly reported that acute ED consumption resulted in increased systolic and diastolic blood pressure across the pooled results (41). Although the meta-analysis did not find evidence for increased heart rate, the researchers noted the need for well-designed studies before any conclusions can be made.

Caffeine toxicity is believed to occur above 400 mg/day for adults, 100 mg/day for adolescents (12–18 years), and 2.5 mg/kg of body weight for children (<12 years), with serious symptoms often related to cardiovascular effects (42). In the 1-year period between October 2010 and September 2011, the U.S. National Poison Data System received 4,854 ED-related calls, including major adverse events such as seizure, dysrhythmia, and tachypnea (42). Data from Australian poisons centers confirm these major symptoms of recreational or accidental ED intake among children and adolescents, in addition to palpitations, agitation, and tremor (43). Given that these data relies on self-reported signs and symptoms and most consumers may not readily identify ED as a poison, it is likely that ED-related toxicity reports are underestimated. It is believed that the potential for caffeine toxicity from ED is greater than other caffeine sources such as coffee or tea due to inadequate labeling and greater volume of consumption driven by heavy advertising promoting “more is better,” especially among children and youth (5).

Sugar-sweetened beverages, which refer to beverages with added sugar such as soda, fruit juice, and many ED, are consistently associated with long-term negative health effects particularly among children and adolescents (44–46). Primarily, SSBs have been linked to overweight/obesity risk and metabolic conditions such as type 2 diabetes (44, 47–49), potentially through the low satiety of SSBs and consumers not sufficiently reducing total energy intake to account for the additional calories of SSBs (50). In addition, consumption of SSBs increases blood glucose and insulin levels, contributing to a high glycemic load which is associated with glucose intolerance and insulin resistance (48). SSBs are also associated with a high prevalence of dental caries, wherein bacteria in the mouth utilize the sugars from SSBs and produce acid that decays the teeth (51, 52). Finally, renal diseases, specifically renal microvascular damage (53) and accelerated progression of chronic kidney disease, have been shown to be induced by fructose in SSBs in animal-based models (54, 55).

Energy drinks’ consumption is also associated with other commonly reported health problems such as sleep dissatisfaction, tiredness/fatigue, late bedtime, headaches, and stomachaches and irritation (35, 56–59). It is likely that many of these general health complaints are attributable to caffeine or sugar content, but additional research needs to be conducted to confirm this, as well as to assess the potential effect of other constituents. In a cross-sectional study conducted in Finland, consumers of ED had a 4.6 (95% CI: 2.8, 7.7) times greater odds of headaches, 3.6 (95% CI: 2.2, 5.8) times greater odds of sleeping problems, and 4.1 (95% CI: 2.7, 6.1) times greater odds of having an irritable mood compared to non-consumers (57).

The literature generally suggests that the negative health effects of ED outweigh the beneficial effects. However, there are considerable limitations to the existing literature. First, most studies on ED are cross-sectional, limiting the ability to establish temporal relationships and support causality. In addition, many articles used small homogenous populations, often consisting of healthy, young to middle-aged adults, thus limiting generalizability to the U.S. population. Finally, studies specifically examining the effects of other ED constituents are lacking and thus there is limited knowledge on the potential mechanisms beyond those of caffeine and sugar, for which most of the literature exist.

Since 2004, aggressive advertising by ED companies has led to substantial market growth, with a more than 240% increase in sales in the U.S. and worldwide. ED are now available in more than 140 countries (8) and are on track to become a $21 billion industry in the U.S. by 2017 (60).

Energy drinks’ marketing strategies pose a significant public health threat in the U.S. due to the size of their target adolescent market and the marketing strategies they employ. ED face heavy competition for market share with SSB corporations that dwarf them in size, customer base, distribution capability, and ability to invest in advertising (61). To compete, ED companies target the approximately 33.5 million 12- to 19-year olds in the U.S. (62). The public health implications of targeting adolescents are not trivial: adolescents lack maturity in key areas of the brain, are biologically predisposed to have poor impulse control, and are more likely to engage in risk-taking behavior (63). This not only makes them more likely to consume the product on a regular basis but also makes them more vulnerable to identifying and potentially engaging in sexual and risk-taking behaviors depicted in ED marketing.

Adolescents’ vulnerability to the marketing tactics of ED companies is particularly serious given that ED are now omnipresent across multiple vending channels with price points widely affordable to all strata of the population. There are few signs that the scale and targeting of ED marketing will change in the near future. A 2014 study on ED marketing conducted by the offices of several U.S. Senators found that of the sixteen companies they approached, only four agreed to avoid marketing their products to children (64).

Overall, there is a significant lack of ED regulation in the U.S. (65). While the Food and Drug Administration (FDA) enforces a caffeine limit of 71 mg per 12 fluid ounces for soda, ED manufacturers can avoid this by classifying their product as a “supplement,” regulated under the 1994 Dietary Supplement and Education Act and not subject to any caffeine limits (1, 8). That said, many ED companies are moving to marketing their products as beverages to address public concerns that their products are circumventing labeling requirements and also to enable ED to be available to participants of the Supplemental Nutrition Assistance Program, a U.S. nutrition assistance program providing low-income individuals with financial support to purchase food and beverages.

In 2014, the American Beverage Association published the “Guidance for the Responsible Labeling and Marketing of Energy Drinks,” which allowed ED companies to voluntarily commit to a number of industry goals (66). The companies committed to report total quantities of caffeine from all sources, restrict marketing to children, and voluntarily report adverse events to the FDA. However, an assessment report found that compliance to this commitment was staggeringly low (64), with 8 of 12 companies still marketing to children and 4 of 10 companies not willing to report adverse events voluntarily. Other countries facing similar challenge to the U.S. have implemented various approaches to regulate ED. For example, Australia and New Zealand created a unique regulatory category for ED called “formulated caffeine beverages,” and set the upper limit of caffeine from any source to be 320 mg/L (65).

In addition to regulation, some countries have implemented taxation policies as a deterrent to ED consumption. Mexico currently taxes all non-alcoholic beverages with added sugar, including ED, at one-peso-per-liter, with recent assessments reporting that purchases of taxed beverages have decreased by an average of 6% since implementation in January 2014 (67). Similarly successful initiatives have been emerging in some U.S. cities (68).

In addition to being consumed alone, ED are frequently mixed with alcohol, with one study in the European Union finding that 71% of young adults report consuming ED with alcohol (69). This is problematic because individuals who drink alcohol-mixed ED consume more alcohol than if they were drinking alcohol alone (70, 71). Researchers attribute this to the fact that consumption of ED masks the signs of alcohol inebriation, enabling an individual to believe they can still safely consume more alcohol, leading to “awake drunkenness” (72). As a result of this increased alcohol consumption, those who drink alcohol-mixed ED are more likely to experience severe dehydration and alcohol poisoning (73). This negative health trend is particularly concerning as it disproportionately affects underage individuals and has been linked to binge drinking, alcohol-dependence behaviors (70) and drunk driving (74).