Energy Drinks: Performance Effects and Safety Concerns
Energy drinks are becoming a larger, more controversial topic in the world of athletics. This article summarizes studies that look at the effects of energy drinks on performance.
Energy drinks have become very controversial because of their alleged
capacity to enhance performance and because of their potential health
risks. Is the controversy about either their benefits or dangers valid?
Do they help both aerobic (endurance) and anaerobic (speed, power, or
weightlifting) performance? Are they helpful enough to justify their use
despite potential harm? This short paper will attempt to answer these
Ergogenic (from the Greek “ergon,” meaning “work”) aids are ingested
to enhance energy utilization in athletes and have been used for
hundreds, possibly even thousands, of years. Energy drinks are a
relatively new entry into the ergogenic marketplace and are heavily
marketed. They arrived on the scene about 9 years ago, and the demand
among an ever-broader demographic has continued to increase
Energy drink sales figures for the 2005 calendar year
showed Red Bull at the top with around $262 million in sales. Monster
sold about $81 million, Rockstar $67million, and Full Throttle $40
million (2). According to Report Buyer, in 2002 the energy drink market
was about $1.2 billion and progressed to an estimated $6.6 billion in
It does not appear likely that the market will slow down any time
soon, which makes answering these questions regarding their risks and
benefits even more important.
Energy drinks are typically composed of a carbohydrate source
(glucose, maltodextrin), B vitamins, caffeine, and possibly other minor
ingredients, such as the amino acids taurine and L-carnitine and some
herbs. Despite the great deal of data on caffeine and the use of
carbohydrates to enhance aerobic exercise performance, (3, 9-11, 18, 29,
30) there is little data on the effects of energy drinks on exercise
performance, especially from randomized controlled trial formats.
Effects of Energy Drinks on Aerobic Exercise Performance
Candow and colleagues investigated the effects of a sugar-free Red
Bull energy drink on high-intensity run time to exhaustion in young
adults(4). Physically active university students (9 men, 8 women, aged
21 ±4 years) participated in a double-blind, crossover,
Each subject was randomized to the supplement
group (sugar-free Red Bull at 2 mg/kg body mass of caffeine) and a
non-caffeinated, sugar-free placebo (tonic water with lime juice) with 7
days between tests. A run time to exhaustion test at 80% VO2 max was
performed while rating of perceived exertion (RPE) was assessed
immediately after exercise. They found no differences in run time to
exhaustion (Red Bull: 12.6 ±3.8 minutes, placebo: 1.8 ±3.4 minutes), or
perceived exertion on a Borg scale (Red Bull: 17.1 ±2.0, placebo: 16.6
±1.8) between groups.
Ivy and company investigated the effects of a commercially available
energy drink ingested before exercise on endurance performance (17).
This study also used a double-blind, randomized, crossover design.
Subjects (6 male and 6 female) were trained cyclists (mean age 27.3 ±1.7
years, mass 68.9 ±3.2 kg, and VO2 peak 54.9 ±2.3 ml/kg/min) and arrived
to the lab after an overnight (12-hour) fast.
They consumed 500 ml of
either a flavored placebo or Red Bull Energy Drink (160 mg caffeine with
54 g carbohydrate). Performance was measured as time to complete a
standardized amount of work equal to 1 hour of cycling at 70% wVO2 max.
Performance improved with the energy drink compared with placebo (3,690
±64 s vs. 3,874 ±93 s, p < .01), although there was no difference in
ratings of perceived exertion (RPE).
Respiratory exchange ratio (RER)
was also evaluated to investigate substrate (fat or carbohydrate)
utilization by open-circuit spirometry and did not differ between
The conflicting results of these two studies from Candow and Ivy may
be related to the different study designs and the mode of exercise. For
example, Candow (4) used a run to exhaustion yet Ivy (17) used a cycling
time trial. Furthermore, it remains difficult to pinpoint the potential
ergogenic ingredient(s) in energy drinks, such as carbohydrates and
Carbohydrates and fluids have been repeatedly shown to be
ergogenic when given before and during endurance exercise (18, 19, 22,
24, 27-30). There is substantial information that shows caffeine can
improve endurance performance (9, 10), but the combination of
ingredients in energy drinks may inhibit this improvement in
Effects of Energy Drinks on Anaerobic Exercise Performance
Not all athletes engage in aerobic-based sports, as some sports are
anaerobic in nature. With that said, perhaps there is an ergogenic
effect of an energy drink taken pre-exercise in anaerobic-based
performance? Forbes and company studied the effects of Red Bull at 2
mg/kg body mass caffeine as compared to those of a placebo
(noncaffeinated Mountain Dew with lemon juice) (8).
physically active subjects (12 men, 4 women, aged 24 ±6 years)
volunteered for the study. After a familiarization trial, subjects were
randomized to groups and accordingly ingested either the supplement or a
placebo 60 minutes before exercise.
Muscle strength and endurance was
measured by 1-rep max (1RM) bench press test where subjects performed 3
sets of reps to volitional fatigue at 70% of their 1RM. Anaerobic power
was assessed by repeated 30-second Wingate cycle ergometer tests with
resistance set at 7.5% of their body mass.
The Red Bull group was found
to increase the total bench press reps vs. that of the placebo group (34
± 9 reps vs. 32 ± 8 reps, p<0.05), but had no effect on peak
anaerobic power (701 ± 124 W vs. 700 ± 132 W) or average power (479 ±74 W
vs. 471 ±74 W) for the Red Bull vs. placebo, respectively. From this
study, Red Bull improved bench press rep performance but not anaerobic
Despite the great deal of data on the main active ingredients in
energy drinks (caffeine and carbohydrates), there is limited data to
show that they enhance aerobic or anaerobic exercise performance.
The albeit brief history of energy drinks contains many case reports
of acute short-term effects, but substantial data to determine the
validity of any and all claims regarding short- or long-term effects is
yet to come (5-7, 25). More safety data is always a good thing, but that
argument could be made for any supplement or even some common food
items. Energy drinks are no different in this regard.
The main active stimulant in most energy drinks is caffeine since it
is cheap and effective. Recently, Canada passed new rules limiting
caffeine levels at 180 mg per drink (12). For comparison, the average
cup of coffee contains between 40 and 150 mg caffeine, although
specialty coffees may contain much higher doses (20).
"The dose makes the poison" – Paracelsus
A substance can produce the harmful effect once it reaches a high
enough dose. Caffeine is one of the most studied substances in the food
supply and has a long history with overwhelming scientific evidence
supporting its safety when consumed in moderation (13).
overdoses in adults are relatively rare and require ingestion of a large
amount of the drug, typically in excess of 5 g or 5,000 mg (20). At 120
mg caffeine per average cup of coffee, that amounts to about 41 cups of
coffee. While there are a handful of case reports of caffeine
overdosing in the literature (16, 20, 26), they are very rare especially
considering the broad accessibility of caffeine.
The effective dose where an ergogenic effect is seen is about 2-6 mg
caffeine/kg body mass; so a 220-pound athlete would need about 200 to
600 mg or 1.5 to 5 averaged-sized cups of coffee to potentially enhance
performance (9). Too much caffeine, on the other hand, can potentially
be ergolytic (detrimental to performance) (9). For athletes monitoring
performance, an increased dose of caffeine will show a performance
drop-off well before they approach the amount close to acute caffeine
Based on the data reviewed by Nawrot and colleagues in 2003(23), up
to 400 mg of caffeine daily was not associated with any adverse effects
in healthy adults. The study did state that children should limit their
consumption to less than 2.5 mg/kg bodyweight/day. Higdon and company
(14) presented data (also in children), that no adverse effects were
seen with doses under 3 mg/ kg bodyweight/day; however, the exact amount
of caffeine will vary from person to person based on genetics, body
mass, and sensitivity.
For reference, a youth athlete weighing 120 lb (54.4 kg) at 3 mg/kg
body mass caffeine calculates out to 163 mg of caffeine per day, or
about 2 servings of an average energy drink (average caffeine per
serving of Red Bull is 81 mg).
While clear-cut recommendations for athletes do not exist, some
groups such as the Mayo Clinic do not recommend energy drinks for
athletes participating in exercise lasting less than 1 hour (15), but
also admit there is a lack of long-term data to support this conclusion.
Even when consumption of an energy drink results in a statistical
increase in performance, this translates into a very small real-world
change; it will not transform anyone into the next Olympic athlete
overnight. The main ergogenic ingredient (caffeine) has a great safety
record when used in moderation.
The longest-term data available in the
literature on one type of energy drink (Celsius) taken once a day for 10
weeks did not show any change in clinical markers for hepatic, renal,
cardiovascular, or immune function, and revealed no adverse effects in
response to its consumption (21).
Unfortunately there are not any other
data investigating other types of energy drinks for a similar length of
time, especially accounting for a higher total dose and frequency. Based
on current data, it appears that an occasional energy drink with regard
to acute health risks is safe; but long-term studies have not yet been
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