Energy Drinks: A Clinical Primer and National Data Update

Abstract

This article describes estimates of energy drink uptake using national-level data in the US and provides clinical strategies for evaluating patients with unhealthy energy drink consumption. Our approach is grounded in the paradigm of harm reduction, which supports incremental change while recognizing people’s dignity, autonomy, individualism, and accountability.¹ Rather than urge complete abstinence, we emphasize the importance of helping people understand energy drinks’ potential harmful effects independently of whether individuals are ready to abstain from energy drinks.

Caffeine Content Unknown in Energy Drinks

Energy drinks represent nearly 10% of all sugar-sweetened beverages worldwide.² The target consumer market for energy drinks consists heavily of young adults,³ a population less tolerant of caffeine’s effects and at heightened risk of adverse effects.³ Surveys suggest that half of college students consume at least one energy drink per month, with common reasons including the desire to increase energy, reverse the effects of alcohol (a misconception described in detail in article), and/or compensate for poor sleep.⁴

Protected by the 1994 Dietary Supplement Health and Education Act, energy drinks are grouped together with natural dietary supplements described as Generally Regarded as Safe (GRAS) by government regulators, owing to the inclusion of specialty ingredients not commonly found in juices and soft drinks such as amino acids (taurine), yerba mate, guaraná, ginseng, B-complex vitamins, and other ingredients.⁵ The stimulating effects of energy drinks are not only due to caffeine and specialty ingredients but also the rush caused by a high dosage of carbohydrates and sugars.⁶

Due to their GRAS status, energy drinks often do not report their caffeine content, nor provide warning labels advising proper use.⁷ In cases where drinks do disclose their content, labeling inaccuracies are common.⁵ Some energy drinks may contain up to 70% more caffeine on average than the 0.02% caffeine threshold for GRAS products.^8–10 Yet, the FDA has not re-evaluated energy drinks’ GRAS status in recent decades.¹⁰ While most soft drinks fall within the FDA’s limit of no more than 65 mg of caffeine per 12 ounces,¹¹ energy drinks are suspected to contain far greater amounts of caffeine, ranging from 50 to 550 mg per bottle.¹² As shown in Figure 1, energy drinks may sometimes report the quantity of caffeine, yerba mate, and guaraná separately, without disclosing the precise quantity of caffeine contained in the mate and guarana contents.

Figure 1.

Example of nutrition and supplement facts for selected energy drinks (available sale on www.amazon.com)

Energy drinks are altering the debate about the risk/benefit ratio for caffeinated beverages, which has historically been grounded in controversy surrounding whether caffeine use disorder is a valid diagnosis. After all, caffeine consumption is considered “more a dedicated habit” than a risk factor for “compulsive addiction” due to its mood and alertness-enhancing effects at low doses.^{13 14} Most people can consume caffeine throughout the life-span without sustaining functional impairment. Many individuals report improvements in subjective alertness and decreased fatigue immediately after consuming energy drinks,^15,16 supporting the popularity of energy drinks among athletes who report improved short-term strength and endurance.^17–21 While caffeine use disorder remains without formal Diagnostic and Statistical Manual of Mental Disorders (DSM) diagnostic criteria, the DSM-5 recently added criteria for caffeine withdrawal and intoxication, as studies show that caffeine withdrawal and intoxication can cause functional impairment among chronic consumers of caffeine.^22–24 Per DSM-5 guidelines, caffeine withdrawal is defined as prolonged daily use of caffeine with 3+ symptoms, occurring within 24 hours of reduction in use, including headache (the most common symptom³), fatigue, dysphoria, depressed mood, irritability, concentration deficits, and flu-like symptoms.²⁵ Caffeine intoxication is also included in the DSM, with symptoms including insomnia, rambling speech and flow of thought, increased psychomotor activity and restlessness, nervousness and excitement, diuresis, gastrointestinal upset.²⁵

Caffeinated Dietary Supplement Consumption Increase

Because there is limited data on trends in energy drink consumption in the US, we conducted preliminary analyses using the publicly-available National Health and Nutrition Examination Surveys (NHANES), which encompass face-to-face interviews and physical examinations in a nationally representative sample of approximately 5,000 individuals per two-year cycle. The NHANES survey’s dietary supplement questionnaires contain data (i.e., brand, amount, caffeine content) on prescribed and over-thecounter dietary supplements reported by NHANES participants based on past 24-hour recall.

Using SAS 9.4, we computed the number of dietary supplements containing the term “energy” in their product name as a proxy for energy drink consumption. We also calculated the median amount of caffeine content (mg) per supplement, as well as the percentage of supplements (containing “energy” in the product name) consumed more than once daily. As shown in Figure 2, the number of supplements containing “energy” in the product name increased steadily from 2009 to 2020, rising from 14 in 2009–2010 to 44 in 2017–2020. The median caffeine content, across all supplements, increased from 57.4–80mg in 2009–2010 to 135–150 mg in 2017–2020. Whereas 17.9% of dietary supplements containing the term “energy” in the product name were reportedly taken >1 per day in 2009–2010, this figure increased to 29.1% in 2017–2020.

Figure 2.

Caffeine Use Characteristics, NHANES 2019–2020

There are limitations associated with our preliminary analyses. After all, caffeinated dietary supplements in the NHANES data do not capture all available energy drinks, and not all dietary supplements containing the term “energy” are necessarily energy drinks. Yet, such trends have important implications; multiple professional organizations (including the American Academy of Pediatrics²⁶) recommend children and adolescents not consume energy drinks owing to current gaps in our knowledge of caffeine content and risk level. There is also no legal age limit to buying energy drinks, and the overtones of caffeine being a GRAS dietary supplement may lead consumers to believe that “more is better.”³ While studies suggest that energy drink consumption increased nearly 10-fold across children and adolescents in the 2010s,²⁷ up-to-date data remains sparse on the risks and benefits of energy drinks in children and young adults. While death from caffeine intoxication is thought to be rare,²⁸ energy drink-related toxicity reports are also underestimated, as data relies on self-reported signs and symptoms when many consumers may not be able to link their symptoms to energy drink consumption.⁷

Harm Reduction for Safer Caffeine Consumption

Harm reduction (the framework of mitigating risk without the goal or expectation of completely eliminating risk) can be useful for helping patients with unhealthy energy drink consumption, particularly since many patients may not be ready to completely cut energy drinks out of their routine. Rather than help people move from active energy drink consumption to a state of abstinence, harm reduction strategies aim to optimize the safety of energy drink consumption regardless of whether they are ready to cut down. We provide a clinical checklist (Table 1, created via expert clinician consensus) to guide physicians through the evaluation of young adults engaged in unhealthy energy drink consumption.

Table 1.

Clinical Case Challenge: A 21-year-old college student presents to her primary care doctor for recurrent panic attacks and reports that she had not slept for 36 hours. Her history of present illness is significant for one year of sustained low mood “poor quality” sleep, day time fatigue, headaches, stomach aches, passive suicidal ideation, and irritability. Four months ago, she initiated a selective serotonin-reuptake inhibitor, which was up-titrated to a therapeutic dose with limited benefit. She had been diagnosed with attention-deficit hyperactivity disorder (ADHD) at age 16; she had a prescription for amphetamine salts (Adderall XR) in high school but discontinued it in 12th grade. Notably, she reports consuming approximately six energy drinks in the afternoons for the last 2 years. After trying Red Bull for the first time at a college orientation week party (where it was mixed with alcohol), she escalated her energy drink consumption in order to “power” herself through a heavy freshman year course load. Lately, she feels as if she cannot function without energy drinks. What might your work-up look like for this patient?

Framework for an Office-Based Energy Drink Workup Evaluate for Caffeine Toxicity [ ] Physical exam and vitals; electrocardiogram (if clinically indicated) [ ] Readily apparent signs and symptoms of caffeine poisoning should prompt emergency department referral [ ] Complete blood count, pregnancy test, comprehensive metabolic panel, total creatinine kinase, thyroid studies [ ] Dipstick urinalysis; urine drug screen with confirmatory testing and blood alcohol level (if clinically indicated) Evaluate for Treatable Mental Health Conditions [ ] Depression; anxiety disorders; bipolar and psychotic disorders [ ] Attention-deficit hyperactivity disorder; substance use-related problems (i.e., alcohol, vaping/nicotine, marijuana) [ ] Consider referral to psychiatry or counseling/psychotherapy Focus on Preventive Health Care [ ] Primary care follow-up [ ] Dentist referral [ ] Motivational interviewing; discuss why patients were drawn to energy drinks in the first place and whether safer alternatives may exist

Evaluate for Caffeine Toxicity

1. Outpatient generalists must consider whether the patient needs to go to the emergency room

Caffeine intoxication is characterized by tachycardia, neuropsychiatric excitation (ranging from anxiety and tremor to status epilepticus), nausea and vomiting, and metabolic abnormalities including hypokalemia and hyperglycemia.²⁹ As with most poisonings and intoxications, caffeine toxicity exists on a spectrum; patients with mild tremor, mild sinus tachycardia, or mild gastrointestinal upset do not typically require medical intervention, while patients with significant tachycardia, seizure, or intractable vomiting should be referred to the emergency department for evaluation and treatment.

2. Cardiovascular changes, seizures, and gastrointestinal problems are expected in cases of caffeine poisoning

Tachycardia is essentially universal in caffeine intoxication; the rhythm is typically sinus tachycardia, but patients with severe poisoning or comorbid cardiac conditions may experience dysrhythmias, myocardial infarction, or cardiac arrest.³⁰ Although premature atrial contractions were initially thought to be associated with high caffeine intake, studies have shown that this is not the case in the general population, although caffeine intake is associated with an elevated risk of premature ventricular contractions.³¹ Blood pressure is usually elevated, and widened pulse pressures the difference between systolic blood pressure and diastolic blood pressure) may be observed. Hypotension may develop in very severe intoxication due to profound tachycardia resulting in inadequate diastolic filling time or due to peripheral vasodilation mediated by beta-2 agonism. Visits to the emergency department specifically related to energy drink consumption–often for rapid heart rate, palpitations, or chest pain–increased nearly 20-fold in the 2000s.^{32 33} While the moderate consumption of energy drinks (<200 mg caffeine/day) is not known to correlate with clinically relevant cardiovascular changes in most individuals,^{34 35} a recent study more than 50% of a sample of healthy subjects developed a long QTc interval with light activity following energy drink consumption.³⁶ Seizures should be expected in severe caffeine poisoning, and may be recurrent and difficult to control.²⁹ Gastrointestinal upset can be profound and lead to hypovolemia. Hyperglycemia and hypokalemia—both due to the effects of catecholamine release provoked by caffeine—can be useful diagnostic markers.

3. Laboratory evaluation may be needed in some cases

People without readily apparent signs and symptoms of caffeine poisoning do not necessarily need a laboratory evaluation outpatient. In patients with moderate-severe symptoms requiring referral to the emergency department or another acute care environment, clinicians should obtain diagnostic testing including complete blood count, electrolytes, total creatinine kinase, thyroid studies (as thyrotoxicosis can mimic caffeine intoxication), and an electrocardiogram. Testing for serum acetaminophen should be pursued in any patient with a known or suspected intentional overdose. Direct testing for caffeine in blood has limited availability and does not typically play a role in acute management. Clinicians should also consider ordering a pregnancy test in reproductive-age women, as high caffeine consumption has been found to correlate with increased risk for adverse birth outcomes, such as miscarriage and small-for-gestational-age infants.³⁷ The treatment of caffeine intoxication severe enough to require emergency medical care involves targeted sedation with benzodiazepines or other GABAergic sedatives, anti-emetics, intravenous hydration, management of metabolic disturbances, and in very severe cases intravenous beta-blockers, vasopressors, inotropes, and/or emergent hemodialysis.³⁸

Evaluate for Treatable Mental Health Problems

1. Energy drink consumption may suggest unmet mental health needs

Unhealthy energy drink consumption is often comorbid with treatable mood and anxiety disorders.³⁹ Yet, the relationship between caffeine consumption and mental illness is complex. Symptoms of anxiety and depression can be produced by both caffeine withdrawal and caffeine consumption,⁴⁰ and clinicians are recommended to evaluate caffeine intake as part of routine psychiatric assessment.⁴¹ While a cross-sectional study suggested that coffee and caffeine consumption were associated with a lower risk of depressive symptoms.⁴² the authors urged caution on interpretation of their results due to confounding. Other studies found that after adjustment for confounders, people who used energy drinks frequently were more likely to experience depressed mood and heightened sleep difficulty^{43, 44} compared to moderate and infrequent energy drink consumers.⁴⁵ A recent meta-analysis shows that caffeine intake is associated with an increased risk of anxiety disorders in healthy individuals without psychiatric disorders,⁴⁶ while caffeine intake can also exacerbate symptoms in individuals with preexisting anxiety-spectrum disorders.⁴⁷ Studies also found that adolescents with higher levels of caffeine consumption are more likely to experience insomnia compared to peers with lower levels of caffeine consumption.^{48, 49} Caffeine’s effects can be particularly problematic for patients with serious mental illnesses (i.e., bipolar and psychotic disorders) who are sensitive to sleep disruption.^{50, 51}

2. Energy drinks are not a substitute for SSRIs or psychotherapy

Past literature^{52, 53} on the effects of caffeine on mood were conducted on lower risk thresholds than the amounts contained in energy drinks. Improvements to mood from caffeine may be short-lived, as energy drink consumption was associated with a transient decrease in anxiety and depressive symptoms that returned to baseline after the effects of caffeine wore off.⁵³ Overall, it is difficult to differentiate between improvements to mood as a consequence of reversing caffeine withdrawal (among habitual consumers who developed tolerance and dependence) and caffeine’s direct effects on mood and cognition.³

3. Energy drinks are not a substitute for ADHD medication

Teens with ADHD often report using caffeine to “self-medicate” ADHD symptoms. However, the observational nature of existing analyses on the caffeine-ADHD relationship hinders our ability to infer causation.^{54, 55} Consumers of energy drinks were nearly 70% more likely to exhibit symptoms of ADHD (i.e., hyperactivity and inattention) compared to peers who did not consume energy drinks.⁵⁶ On one hand, adolescents with ADHD were twice as likely as peers without ADHD to consume caffeinated beverages in the afternoon and evening;⁵⁷ yet, caffeine consumption was not consistently associated with ADHD symptom severity.⁵⁵ Importantly, psychostimulants such as methylphenidate and amphetamines consistently are significantly more effective than caffeine for the treatment of ADHD.⁵⁸

3. Inquire about whether energy drinks are being mixed with alcohol

The co-consumption of alcohol and caffeine increased in popularity since the 2000s,⁵⁹ with nearly 50% of young adult samples reporting that they used energy drinks in tandem with alcohol.⁴ Consumers often incorrectly believe that caffeine may counteract the CNS depressant effects of alcohol. Yet, in reality, caffeine reduces sleepiness without alleviating alcohol-related impairment (i.e., “wide-awake drunkenness”).⁶⁰ Thus, people may underestimate their degree of impairment while consuming energy drinks with alcohol,⁶¹ and are more likely to experience dehydration and alcohol poisoning than peers who do not mix caffeine and alcohol.⁶⁰ Studies raised concern for increased risk of alcohol dependence,^{62, 63} and driving while intoxicated⁶⁴ among people who consume caffeine and alcohol together. Of concern, chronic alcohol consumption may increase the half-life of caffeine by over 70%.⁶⁵

4. Non-judgmentally, ask your patients about substance use

Studies showed a correlation between energy drinks use and a myriad of non-alcohol substance use-related problems; for instance, US national survey data of middle and high school students illustrated associations between energy drink consumption and 30-day cigarette and marijuana use.⁶⁶ Associations between regular energy drink consumption and smoking among adolescents were also observed in European samples,⁶⁷ paralleled by Canadian studies showing an increase in sensation-seeking, depressive symptoms, and substance use among energy drinks users relative to peers who do not consume energy drinks.⁶⁸

Focus on Preventive Health Care

1. Do not neglect primary care labs and workup

Sugar is the second most prominent ingredient in energy drinks after water, and thus clinicians should evaluate for diabetes^69–71 and dental caries^{7 72} associated with chronic energy drink consumption. Patients may also develop hypertension, cardiovascular problems,^73–75 and renal dysfunction^{7, 76} Because studies suggest that some patients with sleep apnea may turn to caffeine to promote wakefulness,⁷⁷ history should be gathered regarding sleep-disordered breathing, and sleep studies should be considered if clinically appropriate. Studies also suggest that people with narcolepsy may also turn to caffeine for management of drowsiness.⁷⁸

2. Engage your patients in conversation about safer caffeine consumption

Consistent with the spirit of motivational interviewing, clinicians should explore the benefits patients are deriving from energy drinks (i.e., managing an overwhelming workload; relief from depression; influence of social norms). Perceived benefits such as improvements in athletic performance, wakefulness, and reaction time should be explicitly acknowledged and weighed against potential risks. Recognizing that abstinence is not necessarily the goal, clinicians should assess their patients’ readiness for change and discuss caffeinated alternatives to energy drinks that may be safer (i.e., flavored coffee, tea/chai), if patients are open to such discussions. While patients may not be ready to discontinue energy drinks, they may, however, be open to discussion about ways to engage in safer alcohol and drug use.

Conclusion

Caffeine consumption is a multi-faceted phenomenon that has a continuum of behaviors, ranging from excessive daily use to daily use without functional impairment to complete abstinence. Defining risk-reduction levels for energy drinks—a crucial step in any harm reduction initiative—is hindered by a dearth of research investigating the safety and mental health risks/benefits of specialty ingredients in energy drinks and their interactions with caffeine. For instance, while some articles suggest that 100+ mg caffeine/day for adolescents and 2.5 +mg caffeine/kg of body weight for children correlates with increased risk of caffeine toxicity and adverse cardiovascular events,⁷⁹ research has not established clear safety thresholds.⁸⁰ Because there is no consensus on the threshold for safe caffeine consumption, data is urgently needed to inform definitions for energy drink consumption risk levels and illustrate how changes in consumption risk may correspond to functional impairment.