For patients who are overweight or obese, the use of green tea extract supplementation may produce a small, but significant, reduction in blood pressure, according to a new study published in the Journal of Hypertension. Green tea, which is rich in antioxidant polyphenols, has been shown to have a vasorelaxant effect which can benefit cardiovascular health; it may also protect against hyperlipidemia and endothelial dysfunction. In this study, researchers examined what effect both green tea and green tea extract had on blood pressure compared to placebo in overweight and obese participants.

Fourteen studies, involving 971 subjects were included in the analysis. Compared to placebo, green tea or green tea extract produced a significant effect on both systolic (mean difference –1.42mmHg) and diastolic (mean difference –1.25mmHg) blood pressure; however, heterogeneity among these studies was statistically significant for both systolic and diastolic blood pressure. Post-hoc subgroup analysis showed significant blood pressure effect only in patients without baseline comorbidities, but further analysis showed blood pressure reductions in both hypertensive and normotensive participants. As for caffeine content, no significant mean difference in blood pressure was seen in studies using decaffeinated supplementation or caffeinated green tea or green tea extract, but a significant effect was seen in studies where caffeine status was unclear. All of these results, the authors note, should be interpreted with caution given the small sample size.  

The authors conclude that given the low quality of evidence across the studies, more high-quality studies, with larger sample sizes, would be needed to confirm the effectiveness of green tea on blood pressure reduction. At this time, a strong recommendation for green tea or green tea extract supplementation among overweight and obese patients cannot be made.