Monster energy drink: the trials tested energy drinks as a class

No study in our sources tested this brand. What has been tested is energy drinks as a class, and the pooled result is moderate. Across 34 studies published between 1998 and 2015, drinking a caffeinated energy drink before exercise improved muscle strength and endurance by a standardised effect of 0.49 and endurance tests by 0.53, pooled across many different drinks, doses and tests. Sprinting did not improve, at 0.14 with p = 0.06. A standardised effect near 0.5 is a moderate shift in a score on a test, measured in people doing exercise trials rather than in anyone getting through a working day. EFSA puts the caffeine intake that raises no safety concern for healthy adults at up to 400 mg a day spread through the day, and at up to 200 mg in a single dose, counting every source in the day together and excluding pregnancy. The single USDA record on this page is the low carb version rather than the sugared one, and no card here gives the caffeine or the sugar in one can, so nothing on this page lets us hold a can against that 200 mg, or against the 150 mg that the EFSA level works out to for a 50 kg teenager.

The numbers, per 100 g

What your body absorbs

• A systematic review of 32 studies found that 100 to 300 mg of caffeine chewed as gum is absorbed rapidly and positively affected most of the exercise and physiological performance measures those studies used. — 32 exercise studies of caffeinated chewing gum in trained and active people (n = 32 studies) Evidence A source
  100-300 mg or 2-4 mg/kg absorbed rapidly, with a positive impact on most exercise and physiological performance outcomes, no pooled effect size and no comparison against another form

What it does to your health

• In a meta-analysis of 34 studies, drinking a caffeinated energy drink before exercise improved muscle strength and endurance by a standardised effect of 0.49 and endurance test performance by 0.53, while sprint performance did not improve. — 34 studies published between 1998 and 2015 in people performing exercise tests (n = 34 studies) Evidence A source
  ES 0.49 muscle strength and endurance, ES 0.53 endurance tests, ES 0.29 jumping, ES 0.51 sport-specific actions, sprinting ES 0.14 (p = 0.06, not significant)
• Pooling 26 randomised crossover trials in female team-sport athletes, a measured dose of caffeine improved physical performance by a small effect of 0.32 (95% CI 0.22 to 0.42), with repeated sprint ability at 0.43 and agility at 0.42. — female team-sport athletes in 26 randomised, blind, placebo-controlled crossover trials (n = 26 trials) Evidence A source
  Hedges g 0.32 (95% CI 0.22 to 0.42) for physical performance; repeated sprint 0.43, agility 0.42, sprint 0.39, anaerobic power 0.30, jumping 0.29
• Taurine taken as a supplement at 1.5 to 3.0 g a day lowered fasting blood glucose by 5.90 mg/dL (95% CI 9.65 to 2.15 lower) and systolic blood pressure by 4.38 mmHg (95% CI 7.26 to 1.50 lower) across 34 randomised trials in adults. — adults in 34 randomised controlled trials of oral taurine supplementation (n = 34 RCTs) Evidence A source
  Fasting glucose MD -5.90 mg/dL (95% CI -9.65 to -2.15), systolic BP MD -4.38 mmHg (95% CI -7.26 to -1.50), diastolic BP MD -2.54 mmHg (95% CI -3.97 to -1.11)

Safety, limits and interactions

• EFSA puts the caffeine intake that raises no safety concern for healthy adults at up to 400 mg a day spread through the day, and at up to 200 mg in a single dose. — healthy adults in the general population, excluding pregnant women Evidence E source
  Up to 400 mg per day (about 5.7 mg/kg bw per day) and up to 200 mg (about 3 mg/kg bw) in a single dose
• A 37-year-old man was hospitalised with severe low potassium of 2.0 mmol/l and muscle breakdown after drinking more than three cans of energy drink a day, which is at least 480 mg of caffeine. — one 37-year-old man drinking over three cans of energy drink daily (n = 1) Evidence D source
  Serum potassium 2.0 mmol/l, raised creatine kinase, leg paralysis and ECG changes, recovery after intravenous potassium and fluids

What people believe that the data does not support

• In the same meta-analysis the performance gain tracked the taurine dose of the drink (slope 0.0001, p = 0.04) and not the caffeine dose (slope 0.0009, p = 0.21), which is the opposite of how these drinks are usually explained. — 34 exercise studies included in the meta-regression (n = 34 studies) Evidence C source
  Taurine dose to performance slope 0.0001 (p = 0.04), caffeine dose to performance slope 0.0009 (p = 0.21)
• In the EU register of health claims caffeine carries 11 rejected claims and not a single authorised one, including the claim that it enhances physical performance and delays the onset of fatigue. — EU register of nutrition and health claims, snapshot of 2026-09-21 (n = 11 rejected, 0 authorised) Evidence E source
  Claim POL-HC-6841 on physical performance and fatigue was assessed and not authorised
• The taurine claim that the substance supports proper metabolism was put to the EU assessment and was not authorised either. — EU register of nutrition and health claims, snapshot of 2026-09-21 Evidence E source
  Claim POL-HC-8026 on taurine and metabolism was assessed and not authorised

Who this works differently for

• Across 12 studies in 666 people, caffeine improved cycling time trials only in carriers of the CYP1A2 A allele (WMD -0.90, 95% CI -1.48 to -0.33). In C allele carriers it did nothing (WMD -0.08, 95% CI -0.32 to 0.17). — 666 participants in 12 studies, split by CYP1A2 rs762551 genotype (n = 666) Evidence A source
  Cycling time trial WMD -0.90 (95% CI -1.48 to -0.33, p = 0.002) in A allele carriers versus WMD -0.08 (95% CI -0.32 to 0.17, p = 0.53) in C allele carriers
• For pregnancy EFSA sets the no-concern level at 200 mg of caffeine a day from all sources, and for children and adolescents at 3 mg per kg of body weight a day, which for a 50 kg teenager is 150 mg. — pregnant women, and children and adolescents Evidence E source
  200 mg per day in pregnancy, 3 mg/kg bw per day for children and adolescents
• Across 46 studies of children and young people, mostly aged 11 to 18, energy drink use went together with higher odds of headaches, stomach aches, hyperactivity and insomnia, with some sign of a dose-response. — 46 studies, mostly cross-sectional, in participants aged 11-18 in North America and Europe (n = 46 studies) Evidence C source
  Higher odds of health-damaging behaviours and of headaches, stomach aches, hyperactivity and insomnia, with some evidence of a dose-response effect

What is still unknown

• The review that gathered 46 studies on young people ended by saying that the short-term and long-term effects still need to be explored, and ten years on no trial has followed young drinkers over time. — 46 studies in children and young people (n = 46 studies) Evidence C source
  No long-term follow-up studies identified

The bottom line

The usual story about these drinks is that the caffeine does the work. In the meta-regression inside that same 34-study analysis, performance tracked the taurine dose of the drink at a slope of 0.0001, p = 0.04, and did not track the caffeine dose, slope 0.0009, p = 0.21. That is a comparison across studies rather than a test inside one, so it cannot show which ingredient caused the gain. It is still the opposite of how the can is usually explained. Regulators were not persuaded by either ingredient. In the EU register caffeine carries 11 rejected claims and no authorised one, including the claim that it enhances physical performance and delays the onset of fatigue. The taurine claim about supporting proper metabolism was assessed and not authorised either. Non-authorised means the wording failed the assessment. It is not a finding that the effect is absent. Taurine has also been trialled on its own, away from any drink. Across 34 randomised trials in adults, 1.5 to 3.0 g a day lowered fasting blood glucose by 5.90 mg/dL, 95 percent confidence interval 9.65 to 2.15 lower. Systolic blood pressure fell by 4.38 mmHg, interval 7.26 to 1.50 lower. Those trials gave taurine as a supplement to people with cardiometabolic risk, and none of them handed anyone a sugared caffeinated drink, so the result stays with the supplement. Caffeine also behaves differently by form and by genotype. A systematic review of 32 exercise studies reports that 100 to 300 mg chewed as gum is absorbed rapidly and positively affected most of the performance measures those studies used. That review pooled no effect size and set no form against another, and the speed of absorption is its own framing rather than something it measured. In 12 studies covering 666 people split by CYP1A2 genotype, caffeine improved cycling time trials only in carriers of the A allele, by a weighted mean difference of -0.90, 95 percent confidence interval -1.48 to -0.33. In C allele carriers the difference was -0.08, interval -0.32 to 0.17, which is nothing. Wingate and jump tests showed no benefit in either genotype, and that caffeine came as a measured dose rather than in a can. The caution is about dose and about who is drinking. In pregnancy the EFSA level is 200 mg of caffeine a day from all sources, and for children and adolescents it is 3 mg per kilogram of body weight a day, which for a 50 kg teenager is 150 mg. A 37-year-old man was hospitalised with a serum potassium of 2.0 mmol/l, muscle breakdown, leg paralysis and ECG changes after drinking more than three cans a day, which the report put at 480 mg of caffeine or more. That is one case, so it shows what can happen at that intake and not how often it happens. Across 46 studies of young people, mostly aged 11 to 18 in North America and Europe, energy drink use went together with higher odds of headaches, stomach aches, hyperactivity and insomnia, with some sign of a dose-response. Those studies are mostly cross-sectional, so the drinks may mark a pattern of behaviour rather than cause the symptoms. The review that gathered them asked for work on the short-term and long-term effects in young people, and ten years later no trial has followed young drinkers over time. No card here gives the caffeine, sugar or taurine in one can of this product, so every number above describes something other than the drink in your hand.

Sources

1. mned-r4-05 · systematic review
   In conclusion, a low dose of caffeine (100-300 mg or 2-4 mg/kg) in the form of chewing gum is rapidly absorbed and utilized, positively impacting most exercise and physiological performance.
   Nutrients, 2024 · checked 2026-09-24
2. mned-r4-01 · systematic review and meta-analysis
   Overall, ED ingestion improved physical performance in muscle strength and endurance (ES = 0.49; p < 0.001), endurance exercise tests (ES = 0.53; p < 0.001), jumping (ES = 0.29; p = 0.01) and sport-specific actions (ES = 0.51; p < 0.001), but not in sprinting (ES = 0.14; p = 0.06).
   Eur J Nutr, 2017 · checked 2026-09-24
3. mned-r4-03 · systematic review and meta-analysis
   For physical performance, caffeine showed a small favorable effect (g = 0.32, 95% CI 0.22 to 0.42), with statistical evidence for repeated sprint ability (g = 0.43), agility or change in direction (g = 0.42), sprint or speed performance (g = 0.39), anaerobic power (g = 0.30), and jumping performance (g = 0.29).
   Nutrients, 2026 · checked 2026-09-24
4. mned-r4-04 · systematic review and meta-analysis
   Taurine supplementation resulted in significant reductions in fasting blood glucose (MD, -5.90 mg/dL; 95% CI, -9.65 to -2.15)...Subgroup and dose-response analyses indicated that a daily taurine dose of 1.5-3.0 g was more effective in improving these cardiometabolic risk factors.
   Nutr Rev, 2026 · checked 2026-09-24
5. mned-r4-07 · agency risk assessment
   Intakes up to 400mg per day (about 5.7mg/kg bw per day) consumed throughout the day do not raise safety concerns for healthy adults in the general population, except pregnant women.
   European Food Safety Authority, Caffeine topic page, Scientific Opinion on the safety of caffeine, EFSA Journal 2015;13(5):4102 · checked 2026-09-24
6. mned-r4-09 · case report
   A 37-year-old man developed severe hypokalemia and rhabdomyolysis after daily intake of over three cans of energy drink (≥ 480 mg caffeine).
   Ugeskr Laeger, 2026 · checked 2026-09-24
7. mned-r4-02 · meta-regression
   The meta-regression demonstrated a significant association between taurine dosage (mg) and performance (slope = 0.0001; p = 0.04), but not between caffeine dosage (mg) and performance (slope = 0.0009; p = 0.21).
   Eur J Nutr, 2017 · checked 2026-09-24
8. mned-r4-11 · claims register
   POL-HC-6841 Caffeine -Enhances physical performance. -Provides a performance edge -Can delay the onset of fatigue -Can increase exercise intensity/work rate Non-authorised
   EU Register on nutrition and health claims, claim POL-HC-6841, snapshot 2026-09-21 · checked 2026-09-24
9. mned-r4-12 · claims register
   POL-HC-8026 Taurine It supports proper metabolism (uptake of glucose/caffeine). Non-authorised
   EU Register on nutrition and health claims, claim POL-HC-8026, snapshot 2026-09-21 · checked 2026-09-24
10. mned-r4-06 · systematic review and meta-analysis
    In subgroup analyses, acute caffeine intake improved cycling time trial only in individuals with the A allele (WMD = -0.90, 95%CI: -1.48 to -0.33, p = 0.002), but not the C allele (WMD = -0.08, 95%CI: -0.32 to 0.17, p = 0.53).
    J Sport Health Sci, 2024 · checked 2026-09-24
11. mned-r4-08 · agency risk assessment
    Caffeine intakes from all sources up to 200mg per day consumed throughout the day do not raise safety concerns for the foetus....A safety level of 3mg/kg bw per day is also proposed for habitual caffeine consumption by children and adolescents.
    European Food Safety Authority, Caffeine topic page, Scientific Opinion on the safety of caffeine, EFSA Journal 2015;13(5):4102 · checked 2026-09-24
12. mned-r4-10 · rapid evidence assessment
    Several studies identified a strong, positive association between the use of energy drinks and higher odds of health-damaging behaviours, as well as physical health symptoms such as headaches, stomach aches, hyperactivity and insomnia.
    BMJ Open, 2016 · checked 2026-09-24
13. mned-r4-13 · rapid evidence assessment
    More research is needed to explore the short-term and long-term impacts in all spheres, including health, behaviour and education.
    BMJ Open, 2016 · checked 2026-09-24