Acute effects of hibiscus tea versus coffee consumption before prolonged sitting on blood pressure and heart rate variability in adults: a randomized crossover trial

Purpose To compare acute effects of consuming hibiscus tea and coffee before prolonged uninterrupted sitting on blood pressure (BP) and heart rate variability (HRV) in young, healthy adults. Methods In a randomized crossover trial, participants (n = 24; 24.9 [4.9] years old; 50% women; 54.2% with overweight/obesity) completed two 3-hour prolonged uninterrupted sitting sessions after consuming hibiscus tea or coffee. A Polar H10 heart rate (HR) strap connected to a Polar V800 monitor evaluated HRV indices, including HR, standard deviation of normal R-R intervals (SDNN), root mean square of successive differences (RMSSD), low-frequency power (LF), and high-frequency power (HF). A sphygmomanometer (Welch Allyn Connex) measured systolic (SBP) and diastolic (DBP) BP, and mean arterial pressure (MAP) was calculated. HRV indices were natural log-transformed (ln) due to skewness. Generalized linear mixed models with random effects examined the influence of both beverages on BP and HRV while adjusting for baseline values. Results SBP, DBP, and MAP were significantly lower (β = − 4.2, − 3.3, − 3.6 mmHg, respectively), and lnHF (β = 0.3) was significantly higher in the hibiscus tea condition compared with the coffee condition (p < 0.05 for all). No other significant differences were detected for other HRV indices (p > 0.05 for all). Sex- and BMI-stratified analyses suggested potential variation in cardiovascular responses across subgroups, although these findings should be interpreted cautiously as formal interaction tests were not performed. Conclusions These findings suggest that hibiscus tea may have potential to favorably modulate cardiovascular responses to prolonged uninterrupted sitting compared with coffee, although further controlled studies are needed to confirm these effects and establish their long-term implications.