Acute effects of consumption of energy drinks on intraocular pressure and blood pressure

Background: Energy drinks contain a wide variety of ingredients including caffeine, for which there have been conflicting reports regarding its effects on intraocular pressure (IOP) and blood pressure. The aim of this study was to investigate the acute effects of an energy drink (Red Bull (R)) on the IOP and blood pressure of healthy young adults. Methods: Thirty healthy university students of either gender, aged 18-30 (mean 23.20 +/- 2.81) years were randomly selected to participate in this study. The subjects were randomly divided into two groups (experimental and control) and were asked to abstain from caffeine for 48 hours prior to and during the study. Baseline IOP and blood pressure were measured. The experimental group (n = 15) consumed one can of the energy drink (containing 85 mg of caffeine in 250 mL) and measurements were repeated at 30, 60, and 90 minutes, while the control group drank 250 mL of water and were tested over the same time period. Results: When compared with baseline, a significant decrease (P<0.05) in mean IOP at 60 and 90 minutes was observed in the experimental group. There was no corresponding change in systolic or diastolic blood pressure. Conclusion: Our results suggest that energy drinks (ie, Red Bull) produce a significant reduction in IOP but have no effect on blood pressure. These findings may be interpreted as reflecting the effect of the combination of caffeine and taurine in the Red Bull energy drink. This effect may result from the known hypotensive effect of taurine, and warrants further study.