Pomegranate juice consumption influences urinary glucocorticoids, attenuates blood pressure and exercise-induced oxidative stress in healthy volunteers
Catherine Tsang, Gillian Wood & Emad Al-Dujaili
Background and aim: Antioxidants have been postulated to exert beneficial effects on cardiovascular and neurodegenerative diseases by neutralizing reactive oxygen species (ROS). Exercise and metabolic processes are known to produce ROS. Pomegranates are rich in polyphenolic antioxidants. The aim of this study is to investigate the effects of pomegranate pure juice consumption on blood pressure, lipid peroxidation and urinary glucocorticoid levels before and after a moderate exercise bout.
Methods: A randomized placebo controlled 2-arm study was conducted. Participants (2 groups of 10 each) attended two 30 min treadmill exercise sessions (50% Wmax); pre and one week post pomegranate juice (500 ml/day containing 1685 mg total phenolics/l) or water consumption. 24 h urine samples were collected and blood pressure monitored before and after each session. Urinary lipid peroxidation levels (TBARS), free cortisol and cortisone levels were determined in all urine samples using in house ELISA methods.
Results: Pomegranate juice consumption was found to significantly decrease systolic blood pressure (pre-exercise: 141±20.7 to 136.1±17.3, P=0.03 and post-exercise:156.4±17.5 to 149.5±10.2 mmHg, P=0.04), diastolic blood pressure (90.9±11.6 to 87.1±8.7, P=0.04 and 102.6±23.9 to 94.6±20.4 mmHg, P=0.05) and TBARS levels (0.312±0.106 to 0.264±0.098 MDA mM/l, P=0.035). There was no significant change in lipid peroxidation or blood pressure for subjects consuming water. Urinary free cortisol was reduced from 39.1±26.6 to 26.4±16.5 nmol/24 h (P=0.064), however there was a statistically significant increase in urinary free cortisone (28.1±20.4 to 51.9±45.1 nmol/24 h, P=0.045), and decrease in free cortisol/cortisone ratio (1.81±1.24 to 0.82±0.56, P=0.009) following one week of pomegranate juice intake.
Conclusions: Our results suggest that pomegranate juice seems to exert beneficial effects in reducing blood pressure pre/post exercise and lipid peroxidation levels due to exercise-induced oxidative stress. The reduction in blood pressure could presumably be due to the inhibition of 11β-HSD1 activity as evidenced by the reduction in cortisol/cortisone ratio or other mechanisms yet to be investigated.