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The Physiological Effects of 5- Hour Energy Drinks

David Apatov, Ainsley Eberwein, Taylor Klein, Sara Schroeder

Physiology 435 Independent Study

May 6, 2011

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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

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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

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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 5-

Hour Energy drinks. Data should provide information as to whether or not these drinks actually

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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 5-

Hour 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

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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

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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

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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.

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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.

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Tables and Figures:

Figure 1: This depiction shows the noisy data from the EEG machine

Drink BP HR

(Beats/

min)

R-R

(mm)

R-T (mm) P-R (mm) T-P (mm)

#4 Before Placebo 125/90 71 18.8 5 3.6 10.4

#4 After Placebo 125/90 76 17.4 5.6 3 8.6

#5 Before Placebo 110/62 63 20.4 6 3 12

#5 After Placebo 110/62 84 18.2 6 2.8 9.6

#11

Before

Placebo 112/68 57.9 23.8 8.0 6.0 10.0

#11 After Placebo 122/80 55.81 25.0 11.0 5.0 15.0

Table 1: ECG and blood pressure data for Placebo condition

Drink

BP HR

(Beats/min)

R-R

(mm)

R-T

(mm)

P-R

(mm)

T-P (mm)

#7 Before Regular 110/80 79 20.6 6 3.8 10.6

#7 After Regular 120/90 64 22.8 6 3.8 13.4

#8 Before Regular 104/70 70 19.8 6 3.4 11

#8 After Regular 124/68 55 25.4 6.6 3.4 15.6

#10 Regular 107/65 78.0 19.6 6.5 3.0 10.0

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Before

#10 After Regular 111/77 73.0 21.3 6.7 2.9 11.0

Table 2: ECG and blood pressure data for regular 5-hour condition

Drink

BP HR

(Beats/min)

R-R

(mm)

R-T

(mm)

P-R

(mm)

T-P (mm)

#1 Before Decaf 130/70 64 22.8 6.6 4.0 13

#1 After Decaf 125/80 58 23.3 6.6 4.0 13.4

#9 Before Decaf 102/78 92 17.6 5.6 3.0 8.8

#9 After Decaf 110/82 91 17.8 5.6 3.0 9.2

#12

Before

Decaf 128/80 81.4 17.6 7.0 4.0 9.0

#12 After Decaf 120/80 80.0 18.2 6.0 4.0 9.1

Table 3: ECG and blood pressure data for decafinated 5-hour condition

Drink

BP HR

(Beats/min)

R-R

(mm)

R-T

(mm)

P-R

(mm)

T-P (mm)

#2 Before Extra

Strength

100/72 71 22.3 6.0 3.2 15

#2 After Extra

Strength

110/74 72 21.1 6.2 3.2 11.2

#3 Before Extra

Strength

140/70 90 16.7 5.6 3.0 8.8

#3 After Extra

Strength

135/90 82 19.4 6.0 3.0 10.8

#6 Before Extra

Strength

120/80 81 18.2 5.4 3.0 9.3

#6 After Extra

Strength

120/92 76 21.0 6.0 3.2 12.3

Table 4: ECG and blood pressure data for extra strength 5-hour condition

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Figure 2: average heart rate data for each condition

Figure 3: average systolic blood pressures

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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

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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

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5- Hour Energy 16

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