Written By: Hannah Cozby, Texas A&M Dietetic InternMemorial Hermann Rockets Sports Medicine Institute
Edited By: Meredith Parmley, MS, RD, CSSD, LD, Memorial Hermann Rockets Sports Medicine Institute
“Energy drinks” are non-alcoholic beverages, with or without sugar, that usually contain high amounts of caffeine. Total caffeine amounts range from 70 to 300 mg in a 16-oz energy drink.1 Energy drinks also contain plant-based stimulants, amino acids, herbs, vitamins, and other ingredients.2,3 Energy drinks are often marketed to improve energy, weight loss, stamina, athletic performance, and concentration.4
Energy drinks are becoming increasingly more popular, and much of the advertising for energy drink consumption is aimed toward active younger adults and adolescent populations.5,6 For example, children between ages 2- and 11-years old saw, on average, 66 ads on television for energy drinks or shots in 2012. In addition, many of the messages in energy drink marketing appeal to children including sponsorships of young athletes.
Claims of enhanced physical performance from energy drink use while participating in sports raise concerns, particularly for young consumers. Prevalence of energy drink consumption in adolescents has increased over the years. For example, a 2024 study in U.S. female high school athletes did a questionnaire on self-reported energy drink consumption and found out of 203 female high school athletes around the age of 14-16, 64.5% reported use of an energy drink at some point during the last 12-months and more than 25% reported using energy drinks 3-4 times a week or more.2 This frequency is substantially higher than earlier reported ranges of 5- 16% in U.S. high school students.
Despite having a multitude of other ingredients, the stimulant in energy drinks that provides a performance-enhancing effect is caffeine. Caffeine is absorbed within ~45 minutes after ingestion, peaking in the blood anywhere from 15- to 120 minutes, with a half-life of ~5 hours.7 Whereas carbohydrates, protein, and fat from food supply the body with the actual fuel for all body processes, including muscle contraction, through the form of ATP, the “energy” of caffeine does not use this same mechanism.
Caffeine is an “adenosine antagonist”. This means that caffeine blocks the compound adenosine from binding to receptors in the brain which mediate critical functions like sleep, arousal, memory, and learning. When adenosine is blocked from binding to these receptors, the mental processes in the brain are increased and the perception of effort and pain during exercise is reduced.7,8 Studies in adults have shown that low doses of caffeine (<3 mg/kg body weight,
~200 mg) are ergogenic when given prior to or during exercise in a wide variety of exercises and sports in recreationally active and well-trained women and men.
However, these doses have not been studied in adolescents. Very high doses of caffeine (e.g., 9 mg/kg bm) are associated with a high incidence of side effects such as tachycardia, heart palpitations, anxiety, headaches, and insomnia, and do not seem to be required to elicit an performance-enhancing effect.5
Despite the high levels of caffeine and incidence of novel ingredients in energy drinks and other products, consumers have limited information about the contents due to inconsistent and incomplete labeling requirements.6 The US Food, Drug, and Cosmetic Act does not require companies to disclose the caffeine content of either beverages or supplements, and many companies do not disclose this information. The Food and Drug Administration (FDA) only mandates that ingredients be listed in energy drinks, but the individual ingredient amounts themselves do not need to be disclosed.9 Energy drinks and other products often contain high amounts of labeled and even masked caffeine, as well as other substances in variable quantities, which may generate uncertain interactions.10 Therefore, consumers are likely to be exposed to large and variable caffeine doses.11
In addition, carbonated energy drinks often come in larger-sized nonsealable containers intended to be consumed in one sitting. Therefore, consumers may feel obligated to consume an entire container, even if more than one serving is listed, which can put them at risk for consuming higher than recommended doses of caffeine.
Specifically for athletic consumers, it may be challenging for them to ensure they consistently ingest safe and effective doses of caffeine to enhance performance. Other ingredients commonly added in energy drinks such as beta-alanine and creatine can boost performance, however due to the FDA not requiring specific dosages of these dietary ingredients to be disclosed, the amounts of these ingredients added may not be sufficient or may be higher than required to have an ergogenic effect.12
In addition, energy drinks can be contaminated with National Collegiate Athletics Association (NCAA) banned drugs not listed on the label, putting student athletes at risk for testing positive on a drug test and potentially losing their eligibility. A stimulant found among many energy drinks and supplements is Guarana, a Brazilian plant containing “guaranine,” which has about twice the concentration of the caffeine found in coffee beans.10 The NCAA caffeine limit is a urinary level of 15 mcg/mL, which equates to consuming ~500-800 mg of caffeine within 2–3-hours before an event, but this amount may vary between individuals. Therefore, repeated energy drink consumption may cause an athlete to test positive in a drug test for stimulants.
Although healthy people can tolerate caffeine in moderation, serious adverse effects have been reported when consumed in large doses, especially in children, adolescents, and young adults.10 These include, but are not limited to, psychological problems such as anxiety, depression, and insomnia, gastrointestinal disturbances, cardiovascular symptoms such as high blood pressure and tachycardia, and in extreme cases, death.13 Although most cases of sudden cardiac death (~80%) are attributed to underlying coronary artery disease, a non-negligible 5%- 10% of all cases occur in young apparently healthy individuals. Some cardiac manifestations have been reported after high ingestion of energy drinks.
In addition to adverse health outcomes, people can develop a caffeine tolerance, requiring a higher amount of consumption for the same stimulant effect, causing it to be addictive and depended upon for normal function.14 Withdrawal symptoms such as headache, drowsiness, agitation, and irritability can occur when suddenly discontinuing the consumption of caffeine.6 There is insufficient evidence to conclude that energy drinks are safe for consumption in adults or
adolescents to allow “definitive dietary recommendations” to be made regarding safe levels.
There is currently limited research on how energy consumption affects adolescents. The high concentration of caffeine in many energy drink products, together with evidence of frequent and growing energy drink consumption among adolescents, appears to present substantial risks for caffeine toxicity and other health concerns.6 In addition, there is growing evidence of a relationship between energy drink consumption and other negative social, emotional, and behavioral outcomes. Known side effects from caffeine consumption include sleep disturbances, anxiety, irritability, and restlessness.
It has been suggested that athletes who sleep more than 8 hours during weekdays and reach recommended nutrition intake, reduce the odds of injury.15,16 Irregular sleep patterns have been shown to cause temporary impaired recovery and may be associated with injury risk, as well as have negative impacts on sports performance.
Therefore, athletes experiencing sleep disturbances due to excessive caffeine intake may be more prone to injury and have negative performance outcomes. For athletes who experience anxiety, irritability, and restlessness, or those with gastrointestinal sensitivity, caffeine can exacerbate these symptoms and may have a negative impact on performance.
In addition, adolescent populations at potentially higher risk of consumption are those with ADHD, who consume other forms of stimulants, those with eating disorders or disordered eating patterns, and those with other health conditions (e.g., cardiovascular, renal, etc.).
There is currently no proven safe dose of caffeine for children, and energy drinks have been shown to provide no nutritional benefits but can cause potentially dangerous adverse reactions in some vulnerable populations. The American Academy of Pediatrics recommends children and adolescents should not consume energy drinks and children under the age of 12 should not consume caffeine.17 For those 12-18 years old, the suggested limit of caffeine intake is at most 100 mg daily (about two cans of cola or 1 cup of coffee).
For adolescents considering the use of energy drinks or supplements, it is important to be aware of adverse effects, especially for populations at high risk. For proper dosage, limit total caffeine intake to 100 mg per day. If consuming energy drinks, avoid risky behaviors such as rapid intake, drinking a large amount at once, or mixing with alcohol/drugs.
When considering an energy drink or any other form of supplement, ensure the product is third-party tested. Third-party certification means that an independent organization has reviewed the manufacturing process of a product and has independently determined that the final product complies with specific standards for safety, quality, and performance. Some examples of third-party testing organizations are US Pharmacopeia (USP) Convention Dietary Supplement Verification Program, ConsumerLab.com, National Sanitation Foundation (NSF), and Informed Choice.
Athletes who are considering the use of caffeine for performance benefits need to ensure they first are dialed into the fundamentals of proper fueling with nutrition, hydration, adequate sleep, etc. Due to caffeine plasma levels peaking ~ 60 min post-ingestion, a dose < 100 mg consumed approximately 60 minutes before an event may be beneficial. For those in longer events, which caffeine appears to be the most beneficial, ingestion during exercise (mid/later stages) may be more beneficial than ingestion before.8
When determining how caffeine affects performance, a trial should be done during training prior to an event with a third-party tested product to ensure the individual’s performance is not negatively impacted. Further research is necessary to deem energy drink consumption safe or unsafe when consumed as intended and in
combination with athletic activity (before, during, and after) in adolescents. In addition, there may be interactions with the consumption of other stimulants and potentially addictive substances that are commonly consumed by adolescents.
Have questions? Please feel free to talk to an Athlete Training and Health Performance Coach or Meredith Parmley, MS, RD, CSSD, LD, Sports Dietitian with the Memorial Hermann Rockets Sports Medicine Institute. Meredith can be reached at Meredith.Parmley@memorialhermann.org or can be found on Instagram at @meredithdarcienutrition.
References
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