|Year : 2013 | Volume
| Issue : 1 | Page : 20-24
Acute effects of consumption of energy drink on intraocular pressure and blood pressure-pilot study
Jennifer Aleye Ebeigbe, Eki Anita Obahiagbon
Department of Optometry, Faculty of Life Sciences, University of Benin, Nigeria
|Date of Web Publication||19-Apr-2014|
Jennifer Aleye Ebeigbe
Department of Optometry, Faculty of Life Sciences, University of Benin
Source of Support: None, Conflict of Interest: None
Context: Energy drinks are popular caffeinated beverages believed to improve cognitive function and concentration. They contain two main ingredients taurine and caffeine, which have both been reported to have effects on blood pressure (BP) and intraocular pressure (IOP). Aim: The aim of this study is to investigate the acute effects of consumption of energy drinks on IOP and BP of healthy black young subjects. Materials and Methods: A total of 50 undergraduates from the University of Benin, Nigeria, aged 18-30 years (mean 24.43 ± 1.54) were randomly selected to participate in this study. The subjects were of either gender and were divided into experimental and control groups of 25 subjects each. The subjects were told to abstain from caffeine for 48 h prior to and during the study. Baseline IOP and BP were measured. The experimental group consumed one can of Red Bull (containing 85 mg of caffeine in 250 ml) and measurements were repeated at 30, 60 and 90 min while the control group drank 250 ml of water and were tested over the same period of time. Results: When compared to baseline, a significant decrease in mean IOP was observed at 30, 60 and 90 min (P < 0.05) in the experimental group, but there was no significant difference in the mean change of the systolic and diastolic BP (P > 0.05). Conclusion: Results suggest that energy drinks produce a significant reduction in IOP, but have no effect on blood pressure. These findings may however reflect the combined effect of caffeine and taurine, as present in Red Bull.
Keywords: Blood pressure, caffeine, energy drinks, intraocular pressure, taurine
|How to cite this article:|
Ebeigbe JA, Obahiagbon EA. Acute effects of consumption of energy drink on intraocular pressure and blood pressure-pilot study. Afr J Med Health Sci 2013;12:20-4
|How to cite this URL:|
Ebeigbe JA, Obahiagbon EA. Acute effects of consumption of energy drink on intraocular pressure and blood pressure-pilot study. Afr J Med Health Sci [serial online] 2013 [cited 2019 Jan 19];12:20-4. Available from: http://www.ajmhs.org/text.asp?2013/12/1/20/129918
| Introduction|| |
Energy drinks are caffeinated beverages designed primarily to increase the consumer's physical performance.  These beverages contain ingredients like caffeine (80-500 mg) and an amino acid derivative taurine (1000-2000 mg). They also contain other ingredients such as sugar, vitamins and other nutritional supplements.  They come in a variety of brand names such as Red Bull, Climax, Power Horse, Vero energy and Rox. Most popular among them is Red Bull (caffeine [0.03%] and taurine [0.4%]) in a 250 ml can. Red Bull advert claims its active ingredients "give you wings" by improving performance, concentration and reaction speed, vigilance, emotional status and stimulating metabolism. The Red Bull website recommends drinking Red Bull before tests. This has led to increased popularity of this drink among adults, especially undergraduates in our campuses who are involved in stressful mental activities. Many students have turned away from the old traditional practice of drinking coffee to stay awake to drinking Red Bull while studying and before examinations, because, they believe it improve their memory and performance. A survey of energy drink consumption by young people revealed that 51% have reported consuming at least one energy drink per month. 
Researchers have studied caffeine and taurine and have reported that they are the most physiologically active ingredients in energy drinks. 
Caffeine consumption is known to trigger the release of epinephrine, which causes some of the physiological effects like increased heart rate and blood pressure (BP) that are usually reported.  Previous studies ,, on the effects of caffeine on intraocular pressure (IOP) and BP had reported an increase in both variables measured.
Taurine is a non-essential amino acid that is found in high concentration in the brain and acts as both a neuromodulator and neurotransmitter. , It is also present in high quantities in mammalian hearts where it has been shown to increase cardiac stroke volume and may have antihypertensive activity.  Studies , on the effect of taurine on IOP suggest a reduction in IOP. A combination of taurine and 0.5% of timolol has been reported to cause a significant decrease in IOP in rabbits 24 h after instillation.  Studies on the effects of energy drinks on ocular parameters are scant. Steinke et al. investigated the effects of energy drinks consumption on hemodynamic and electrocardiogram parameters in healthy young adults and reported a significantly increased heart rate and BP within 4 h. Ilechie and Tetteh  studied the acute effects of consumption of energy drinks on IOP and BP of young adults in Ghana and reported a decrease in IOP 60 min and 90 min after consumption, there was no change in systolic and diastolic pressure.
Primary open-angle glaucoma (POAG) and hypertension are two common conditions that affect millions of Nigerians. POAG is a major cause of blindness world-wide.  It is characterized by progressive optic nerve deterioration which eventually leads to blindness if untreated. Not much is known of its etiology, but an important established risk factor for its development and progression is elevated IOP. , Furthermore, elevated BP is the single most important predictor of hypertension. Hypertension is an important public health problem world-wide and one of the leading causes of disability or death, due to stroke, heart attack or kidney failure.  Sub-Saharan Africans are more predisposed to glaucoma ,, and hypertension , and because these conditions are influenced by factors affecting life-style, efforts to identify factors that may influence IOP and BP levels are encouraged.  It is against this background that this study was carried out to determine the acute effect of drinking a can of Red Bull, which includes taurine and caffeine, on IOP and BP among young Nigerian undergraduates.
| Materials and Methods|| |
This study was a prospective study that involved 50 healthy undergraduates from the University of Benin visiting the Optometry Clinic for routine eye examinations. They were aged between 18 and 30 years of age. They were recruited by systematic random sampling by picking every third patient from the names of patients entered in the register. The subjects were from various faculties of the University of Benin. A total of 25 subjects were in the experimental group while, the other 25 were in the control group. There were 12 females and 13 males in each group. Both groups were also matched for age with a mean age of 24.43 ± 1.54. Inclusion criteria included subjects who have no history of glaucoma, ocular hypertension, high refractive error, increased systemic BP and diabetes. A detailed systemic and oculo-visual history was taken from the subjects. Relevant questions were asked which had to be adequately answered for the subject to qualify to participate. Prior to the experiment, some basic optometric examinations were carried out on the subjects. This included contact tonometry, distance visual acuity test using the Snellen letter chart and monocular direct ophthalmoscopy to assess the integrity of the posterior segment. BP measurements were also taken. Exclusion criteria included individuals with glaucoma, posterior segment disease, systemic diseases such as hypertension and diabetes.
Subjects who met our inclusion criteria and who were willing to participate in the study were told to return to the Optometry clinic on specified days. Subjects were asked to abstain from caffeine 48 h before coming for the study after the aim and the purpose of this study were explained in details to them. Subjects who reported to the clinic had the procedure explained to them and their written consent obtained. The study was approved by the Department of Optometry Ethics Committee, University of Benin. The study was conducted according to the tenets of the declaration of Helsinki regarding scientific research on human subjects. Two examiners conducted the tests independently and the average of the readings was recorded.
Baseline IOP, systolic and diastolic BP was measured. The experimental group consumed one can of Red Bull (equivalent to 85 mg caffeine in 250 ml beverage). IOP and BP measurements were repeated at 30, 60 and 90 min after consumption. The control group was given 250 ml of water to consume and IOP and BP were measured over the same period of time. The IOP measurement was done between 10 am and 12 noon, to minimize the influence of diurnal variation. The hand held Kowa applanation tonometer was used. BP was measured using manual mercury sphygmomanometer. Data for IOP presented are for the right eyes only because there was no significant difference in the IOP values for both eyes.
Results are presented as means (±standard deviation), differences between measured variables were tested for using t-test. The pre-test and post-test data were analyzed using a paired-sample t-test. Level of significance was set at P < 0.05, using SPSS program for windows (statistical package for the social sciences Inc., version 16; Chicago, IL).
| Results|| |
A total of 25 subjects were in the experimental group while the other 25 were in the control group. The mean age in the experimental and control group was 24.43 ± 1.54 years.
The mean values with standard deviations of all the variables measured in the pre and post tests are presented in [Table 1], [Table 2], [Table 3]. There was no significant difference (P > 0.05) between the experimental and control group with respect to baseline parameters of IOP, systolic and diastolic BP.
|Table 2: Mean systolic blood pressure at different time intervals for each group |
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|Table 3: Mean diastolic blood pressure at different time intervals for each group |
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There was a decrease of ≤2 mmHg in 21 subjects, while there was no change in 4 subjects, among the experimental group. 22 subjects had <1 mmHg decrease in IOP, while 3 subjects did not show any change among the control group. Compared with baseline, mean IOP for the experimental group decreased significantly at 30 and 90 min (by 1.20 ± 1.56 mmHg and 1.17 ± 1.58 mmHg, respectively, P < 0.05). There was no significant change in IOP from baseline at any of the time period measured, P > 0.05, among the control group. This is shown in [Table 4] and [Table 5].
There was no significant change in systolic BP P > 0.05, in both the experimental and control groups from baseline at any of the time period measured. Furthermore, no significant change was observed in diastolic BP from baseline at any of the time period measured, P > 0.05.
| Discussion|| |
Energy drinks have been around for a long time, but they have only just become popular in the markets in the last few years.  These drinks contain high amounts of caffeine and taurine, which have been reported to influence IOP and BP levels. , Available evidence suggests that caffeinated beverages have varying effects on IOP in a different group of individual. Although some, ,, had reported increase in IOP and BP, others have reported no changes. , Ajayi and Ukwade,  reported a significant transient mean IOP increase of 4 mmHg after coffee intake in normal subjects. George and Odjimogho  also reported an increase in IOP and BP after intake of coffee. In another study,  no significant increase in IOP in healthy volunteers was reported after oral administration of 300 mg caffeine after 60 min.
When compared with baseline our study reported a significant reduction in IOP at 30 min, 60 min and 90 min of consumption of a can of Red Bull in the experimental group when compared with the control group. Our findings are similar to that reported by Ilechie and Tetteh  who studied the effect of energy drink on intraocular and BP of students from the University of Cape Coast in Ghana. They reported a significant decrease in IOP after ingestion of a can of Red Bull at 60 and 90 min. However, our study differs from theirs because significant change from baseline was recorded in our study beginning from 30 min after consumption of Red Bull and at subsequent time intervals. There are arguments over the effect of energy drink on BP. One study reported an increase  while another reported a decrease.  In this study, we did not record any significant change either in systolic or diastolic BP in the experimental group. Our result agrees with that of Ilechie and Tetteh  in this aspect. The effect of drinking water on BP has not been fully established. We did not record any significant change in BP among our control subjects, after ingesting 250 ml of water. However, Ilechie and Tetteh  reported a significant reduction in mean systolic BP in the control group 60 min after consumption of water.
There is some controversy among researchers over the mechanism by which caffeine increases IOP. , Some studies have it that it could be due to a decrease in the facility of outflow of aqueous humor caused by vascular constriction of the aqueous vein resulting from caffeine's inhibition of adenosine, which is said to be a potent vasodilator of ocular vasculature. , Others reported that caffeine increases IOP by stimulating the production of aqueous humor by the ciliary body and not by inhibiting aqueous drainage through the trabecular meshwork. ,, Taurine is a 2-aminoethane sulfuric acid that has been reported to have hypotensive activity. It has been reported to decrease systolic BP by an average of 9 mmHg as compared to a 2 mmHg decrease in placebo. ,, Taurine has also been shown to influence IOP levels. 
The reduction in IOP recorded in our study after ingestion of energy drink could therefore be ascribed to a possible dominant hypotensive effect of taurine as against the hypertensive effects of caffeine as available in the existing literature. It should also be borne in mind that apart from the active ingredients caffeine and taurine, contained in energy drinks, other ingredients present in it could exert some form of influence which we unfortunately, have not accounted for. The small sample size used in this pilot study is another factor to put into consideration in interpreting our results. Hence, our findings should be interpreted against this backdrop. To remove these limitations, we suggest that future studies be done with caffeine and taurine, or with taurine only, using a large sample size so as to be able to substantiate this finding.
| Acknowledgment|| |
The authors wish to acknowledge the assistance of Dr. Rejoice Nkechi Duruohia in the collection of data for this work.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]