5- Hour Energy 1
The Physiological Effects of 5- Hour Energy Drinks
David Apatov, Ainsley Eberwein, Taylor Klein, Sara Schroeder
Physiology 435 Independent Study
May 6, 2011
5- Hour Energy 2
Abstract:
The use of caffeinated beverages and energy drinks has radically increased in recent
years. Of all the energy drinks on the market, 5-Hour Energy is unique. It is small compared to
other products, only 1.93 ounces, yet the “regular” drink contains close to 207 mg of caffeine.
For such a widely used product, there has been little research on its physiological effects. We
hypothesized that the regular and extra strength drinks would lead to increases in heart rate, heart
rhythm irregularities, blood pressure, and brain activity. We hypothesized that the decaffeinated
drink would have no effect on blood pressure and would lead to a decrease in heart rate and brain
activity. To record these measurements we used a manual blood pressure cuff, an ECG machine
for heart activity and heart rate, and an EEG machine for brain activity. Due to limited
knowledge and experience with the EEG, we were unable to properly analyze the EEG data. This
prevented us from running any statistical tests on brain activity. The effects of the regular drink
on systolic blood pressure and heart rhythm irregularities (binning) showed a trend towards
increased levels after consumption. After performing T tests with a 95% confidence interval,
none of our data showed any statistical significance. This suggests that 5-Hour Energy drinks
have no consistent effects on human physiology. However, previous studies imply that the
ingredients of 5- Hour Energy drinks should have physiological effects, so future researchers
should perform this experiment on a larger scale with many more participants.
Introduction:
There are various types of energy drinks on the market today. All of these energy drinks
vary in their contents and all claim to provide a boost of energy and a feeling of alertness. Of all
of the energy drinks, 5- Hour Energy controls 12 percent of the energy drink market (CBS
5- Hour Energy 3
Interactive, 2011). Although it is very widely used, there is very little published research that
focuses specifically on the physiological effects of the three different types of 5-Hour Energy
(regular, extra strength, and decaffeinated). This research experiment focuses on the effects of
these drinks on blood pressure, heart rate, heart rhythm irregularities, and brain activity.
The regular 5- Hour Energy drink contains 207mg of caffeine, the decaffeinated drink
contains an insignificant amount of caffeine (6mg), and the extra strength drink advertises a
higher caffeine content but does not provide an exact number (Living Essentials, 2011). The
regular 5-Hour energy drink claims that each drink contains an amount of caffeine comparable to
“a cup of premium coffee” while the Extra Strength drink claims that each drink contains
caffeine comparable to “12 ounces of premium coffee.” Previous research has shown that
caffeine has various effects on the human body. Caffeine has a noticeable effect on blood
pressure. Research shows that caffeine intake significantly raises both systolic and diastolic
blood pressure. One research report shows a 0.5-2.0 mmHg increase in systolic and diastolic
blood pressure after consumption of 250- 300 mg of caffeine (Myers, 2004). Caffeine also has a
noticeable effect on heart rate and rhythm. Caffeine is a central nervous system stimulant. By
stimulating the central nervous system, it causes unevenness in heart rhythms and an increase in
heart rate (Food and Drug Administration, 2007). Along with effects on the heart and blood
pressure, caffeine intake has a significant effect on brain activity. Studies show that caffeine
interacts with neuronal inhibitors in a way that leads to increased neurotransmitter release and
neuronal firing rates (Fredholm et al., 1999).
5-Hour Energy drinks also contain various other ingredients that claim to provide energy.
Of these ingredients, vitamin B12 and taurine have the highest concentrations in the three 5-Hour
5- Hour Energy 4
drinks. These energy drinks contain a synthetic form of vitamin B12 called cyanocobalamin.
While the 5-Hour Energy producers claim that its drink’s B12 supplementation has beneficial
effects on one’s energy, research shows that cyanocobalamin supplementation has little to no
effect on cognitive function in older men (Ford et al., 2010). While vitamin B12 may not have
any effect, rat studies show that taurine supplementation may have beneficial effects. Taurine
administration decreased rat anxiety in three different anxiety tasks. Researchers conclude that
taurine may have an anti-anxiolytic effect on the central nervous system (Kong et al., 2006).
We predict that the three different 5-Hour Energy drinks will have varying effects on
participants’ blood pressure, heart rate, heart rhythm irregularity, and brain activity. The regular
energy drink will lead to an increase in heart rate, blood pressure, and brain activity compared to
baseline levels. Due to its claim to provide a greater amount of energy, we predict that the extra
strength drink will lead to a greater increase in these three variables compared to baseline levels.
We also predict that the regular and extra strength energy drinks may lead to heart rhythm
irregularities. Taking into account the fact that the decaffeinated drink only contains 6mg of
caffeine, we predict that the caffeine content will have an insignificant physiological effect.
However, we predict that the presence of taurine in the decaffeinated drink will lead to a
decrease in heart rate and brain activity and have no effect on blood pressure compared to
baseline levels. If this is the case, we assume that the decaffeinated drink actually will have an
anti-anxiolytic rather than energy boosting effects. The 5-Hour company advertises the
decaffeinated drink as an energy boost, and this may create a false sense of energy.
This study will provide much needed physiological data related to the effects of these 5Hour Energy drinks. Data should provide information as to whether or not these drinks actually
5- Hour Energy 5
provide energy boosting effects. Researchers anticipate that this study’s findings will address
concerns of false advertising related to this small drink’s large claims. Considering this drink’s
high cost of around four dollars per bottle, the American public should be aware of the drink’s
true effects.
Materials and Methods:
For our experiment, we will take four physiological measurements both before and after
the administration of a 5-Hour Energy drink or a placebo. The placebo will function as a control
condition and consists of 1.93 ounces of water mixed with the same sweetener found in the 5Hour drinks (this sweetener is sucralose which is found in splenda). We will use an EEG to
measure brain activity, an ECG to measure heart rhythm and heart rate, and a blood pressure cuff
to measure blood pressure. We will acquire baseline measurements for all of the previously
mentioned physiological variables while the participant relaxes in a chair wearing ear plugs and a
blindfold to minimize environmental distractions. We will record the EEG for 90 seconds so as
to best obtain a viable sample of brain activity free from environmental distractions or
movements. We will obtain an ECG recording for approximately 30 seconds in order to
determine baseline heart rhythm and heart rate.
Since studies having to do with consumption of products are highly variable depending
upon what the participant has previously consumed, we will take measurements early in the
morning so as to minimize effects of different products consumed throughout the day. Also, we
will require that participants have not consumed any caffeine that morning so that the caffeine in
the 5-Hour Energy is the only recent source of caffeine. Caffeine tolerance can vary the strength
of caffeine’s physiological effects (WebMD, 2011). In order to account for this, we will use a
5- Hour Energy 6
caffeine usage survey to limit our experiment to participants that have very similar caffeine
usages. We will limit our study only to those who drink one caffeinated beverage every day. This
survey will ensure that all of our participants have similar tolerances to the effects of caffeine.
After the baseline measurements are recorded, the participant will consume either an
entire 5- Hour Energy drink (regular, extra strength, or decaffeinated) or an equal amount of
sweetened water as a placebo. We will randomly select participants to take each type of drink,
being sure to have at least one male and one female for each condition. Because 5- Hour Energy
is advertised to have effects within minutes, we will wait 20 minutes before taking experimental
data in order to allow the drink to have its advertised maximum effect (Living Essentials, 2011).
After a 20 minute rest interval, we will again measure all four physiological variables, and we
will again eliminate environmental distractions by providing the participants with earplugs and
blindfolds.
Results:
The survey data provided information on each participant’s normal caffeine intake. The
majority of participants consumed one caffeinated drink per day. Those that consumed more than
one caffeinated drink or zero drinks per day were excluded from this study.
Data was obtained for blood pressure, heart rate, and heart rhythm for all participants in
this study. This data is summarized in tables 1-4. Data from the EEG was very difficult to
analyze. The readings were very “noisy” and difficult to read (figure 1). None of the EEG
readings produced recognizable waves in which researchers could determine amplitudes and
5- Hour Energy 7
frequencies. Realizing that the EEG data could not be properly analyzed, EEG data was only
taken for about half of the participants.
“Binning analysis” was utilized in order to determine variations in heart rhythm. The
measured distances between 10 R-R waves were categorized into small ranges. By comparing
the number of categorizations in the baseline and post-consumption conditions any changes in
heart rhythm irregularities were determined. These results are depicted in figure 5.
A paired T-test with a 95% confidence interval was performed on heart rate, systolic
blood pressure, diastolic blood pressure, and R-R binning (using the number of categorizations
between R-R waves within each ECG reading) data. These results are depicted in table 5.
Tables 1-4 display all data related to ECG and blood pressure. Statistical analysis showed
no significant differences in these variables when comparing the baseline and post-consumption
values. However, the regular 5- Hour Energy drink showed a trend towards a significant increase
in systolic blood pressure. Based on the binning data, the regular 5- Hour Energy drink also
showed a trend towards a significant increase in heart rhythm irregularity. Figures 2-5 show
comparisons of all baseline and post-consumption data for all variables.
Discussion:
Contrary to hypotheses, there were no statistically significant changes in heart rate for
any of the four conditions. Although previous studies show that caffeine induces increases in
heart rate, the regular and extra strength drinks did not lead to any significant changes in heart
rate (Food and Drug Administration, 2007). In addition, the decaffeinated drink did not show any
hypothesized decreases in heart rate although it contained taurine and an insignificant amount of
5- Hour Energy 8
caffeine. Previous studies show that taurine can have depressive and anti-anxiolytic effects on
the heart, but this was not the case for this study based on the decaffeinated results (Kong et al.,
2006). It is possible that the combination of caffeine and taurine in the caffeinated 5- Hour drinks
counteracted each other’s effects and lead to the lack of any significant changes in heart rate.
Similarly, the presence of other ingredients, such as B12, in the decaffeinated drink could have
counteracted taurine’s reported effects on heart rate.
Blood pressure data also showed no statistically significant changes in diastolic or
systolic pressures for any of the four conditions. Again, it is believed that this may be due to the
combination of all of the ingredients in the 5- Hour drinks. There was a trend towards a
significant increase in systolic blood pressure in the regular 5- Hour condition. It seems that the
caffeine would explain this slight trend towards an increase in systolic pressure due to its
reported effects of increasing heart activity (Food and Drug Administration, 2007). It is unclear
as to why this would be the case with the regular drink but not with the extra strength drink.
Again contrary to hypotheses, there was no significant changes in heart rhythm
irregularties for any of the four conditions. Although caffeine is tied to increases in heart rhythm
irregularities, the other ingredients in the energy drinks could have counteracted these effects.
Another explination for this finding may lie in the fact that the majority of the participants in our
study were young healthy adults. A healthy and young heart may not be as susceptible to
changes in heart rhyth. In the regular 5- Hour drink condition, there was a trend towards a
significant increase in heart rhythm irregularity, however it is again unclear as to why this would
be the case with the regular drink but not the extra strength drink.
5- Hour Energy 9
If given more resources and time, researchers would have been able to determine the
individual effects of each of the active ingredients in the 5-Hour drinks. This study suggests that
the combination of the caffeine, taurine, B12, and other ingredients in the drinks has a unique
physiological effect. Considering the small amount that has been determined about each of these
ingredients individually, it is impossible to determine what the combined effect of all of these
may be. A larger study with more participants may provide a more reliable description of the
physiological effects of ingesting all of these ingredients together in one 1.93 ounce drink.
While conducting this experiment we encountered many limitations. Researchers had a
limited amount of time to gather enough participants to allow for any significant results. There
was also very limited funding for this experiment. Each experiment required one 5-hour energy
drink at the cost of around four dollars. This limited the number of participants that researchers
were able to recruit for the study. Also, all of the participants were all healthy college students.
A less homogenous group of participants would most likely provide a better explanation of the
effects of these drinks on the American public. The EEG also brought about limitations. With
proper training and experience with the EEG machine and data presentation software,
researchers will be better able to analyze brain activity data.
This study may not provide any definitive conclusions, but it provides a start to the much
needed research on the 5- Hour Energy drinks. With the growing market of unexplored energy
drinks, it is important for consumers to know the exact effects of these drinks. Future research
should include many more participants in order to allow this study’s insignificant trends to
potentially reach significance. This research design holds a lot of promise for future findings.
This study’s researchers encourage a continued focus on this topic.
5- Hour Energy 10
Tables and Figures:
Figure 1: This depiction shows the noisy data from the EEG machine
Drink
BP
HR
(Beats/
min)
71
76
63
84
57.9
R-R
(mm)
#4 Before Placebo
125/90
18.8
#4 After
Placebo
125/90
17.4
#5 Before Placebo
110/62
20.4
#5 After
Placebo
110/62
18.2
#11
Placebo
112/68
23.8
Before
#11 After Placebo
122/80
55.81
25.0
Table 1: ECG and blood pressure data for Placebo condition
#7 Before
#7 After
#8 Before
#8 After
#10
Drink
BP
Regular
Regular
Regular
Regular
Regular
110/80
120/90
104/70
124/68
107/65
HR
(Beats/min)
79
64
70
55
78.0
R-R
(mm)
20.6
22.8
19.8
25.4
19.6
R-T (mm) P-R (mm) T-P (mm)
5
5.6
6
6
8.0
3.6
3
3
2.8
6.0
10.4
8.6
12
9.6
10.0
11.0
5.0
15.0
P-R
(mm)
3.8
3.8
3.4
3.4
3.0
T-P (mm)
R-T
(mm)
6
6
6
6.6
6.5
10.6
13.4
11
15.6
10.0
5- Hour Energy 11
Before
#10 After Regular
111/77
73.0
21.3
6.7
Table 2: ECG and blood pressure data for regular 5-hour condition
Drink
BP
HR
(Beats/min)
64
58
92
91
81.4
R-R
(mm)
22.8
23.3
17.6
17.8
17.6
R-T
(mm)
6.6
6.6
5.6
5.6
7.0
#1 Before Decaf
130/70
#1 After
Decaf
125/80
#9 Before Decaf
102/78
#9 After
Decaf
110/82
#12
Decaf
128/80
Before
#12 After Decaf
120/80
80.0
18.2
6.0
Table 3: ECG and blood pressure data for decafinated 5-hour condition
Drink
BP
HR
R-R
(Beats/min) (mm)
71
22.3
R-T
(mm)
6.0
#2 Before Extra
100/72
Strength
#2 After
Extra
110/74
72
21.1
6.2
Strength
#3 Before Extra
140/70
90
16.7
5.6
Strength
#3 After
Extra
135/90
82
19.4
6.0
Strength
#6 Before Extra
120/80
81
18.2
5.4
Strength
#6 After
Extra
120/92
76
21.0
6.0
Strength
Table 4: ECG and blood pressure data for extra strength 5-hour condition
2.9
11.0
P-R
(mm)
4.0
4.0
3.0
3.0
4.0
T-P (mm)
13
13.4
8.8
9.2
9.0
4.0
9.1
P-R
(mm)
3.2
T-P (mm)
3.2
11.2
3.0
8.8
3.0
10.8
3.0
9.3
3.2
12.3
15
5- Hour Energy 12
Figure 2: average heart rate data for each condition
Figure 3: average systolic blood pressures
5- Hour Energy 13
Figure 4: average diastolic blood pressures
Figure 5: binning analysis. Y axis represents number of intervals between R-R waves.
Placebo
Regular
Decaf
Extra Strength
Heart Rate
p= 0.36, t= 1.17
p= 0.08, t= 3.50
p= 0.25, t= 1.60
p= 0.27, t= 1.60
Systolic BP
p= 0.42, t= 1.00
p= 0.14, t= 2.40
p= 0.77, t= 0.33
p= 0.78, t= 0.38
5- Hour Energy 14
Diastolic BP
p= 0.42, t= 1.00
p= 0.27. t= 1.53
p= 0.25, t= 1.60
p= 0.16, t= 2.18
Binning
p= 0.67, t= 0.50
p= 0.13, t= 2.50
N/A
p= 0.42, t= 1.00
Table 5: data from paired t tests using a 95% confidence interval
5- Hour Energy 15
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