A Cup of Black Tea Does Not Modify Heart Rate Variability

Background: The stimulatory effects of tea on the autonomic nervous system are well established. There exists, however, no conclusive data on the effects of tea on heart rate variability (HRV). This study's objective was to determine the effects of a cup of tea on these parameters among South Indian subjects. Methods: This interventional study involved a single group of 50 male subjects, aged between 18 and 25 years. The subjects were put through a set of baseline tests that included recording of the heart rate (HR), blood pressure (BP), and HRV indices. They were then given a cup of black tea, and 15 minutes later the same set of tests were conducted. Results: It was observed that tea significantly increased the HR and systolic BP (SBP) and reduced the diastolic BP (DBP). Tea produced a decrease in high-frequency power, suggesting a reduction in parasympathetic activity, but it did not have a significant effect on any of the other HRV parameters. Conclusions: In conclusion, tea stimulates the sympathetic nervous system and inhibits parasympathetic activity.