Short-Term tea consumption is not associated with a reduction in blood lipids or pressure: A systematic review and meta-analysis of randomized controlled trials

Authors: IGHO-OSAGIE, EBUWA - Tufts University; KELLY, CARA - Tufts University; WANG, DEENA - D&v Systematic Evidence Review Consulting; YAO, QISI - Tufts University; PENKERT, LAURA - Tufts University; CASSIDY, AEDIN - University Of East Anglia; FERRUZZI, MARIO - North Carolina State University; JACQUES, PAUL - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; JOHNSON, ELIZABETH - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; CHUNG, MEI - Tufts University; WALLACE, TAYLOR - George Mason University

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2020
Publication Date: 11/13/2020
Citation: Igho-Osagie, E., Kelly, C., Wang, D.D., Yao, Q., Penkert, L.P., Cassidy, A., Ferruzzi, M., Jacques, P.F., Johnson, E.J., Chung, M., Wallace, T.C. 2020. Short-Term tea consumption is not associated with a reduction in blood lipids or pressure: A systematic review and meta-analysis of randomized controlled trials. Journal of Nutrition. 150(12):3269-3279. https://doi.org/10.1093/jn/ nxaa295.
DOI: https://doi.org/10.1093/jn/nxaa295

Interpretive Summary: Some current research suggests that drinking tea is associated with health benefits, specifically lower risk of mortality and heart disease. We conducted a meta-analysis, which is a statistical analysis that combines the results of multiple scientific studies, to better understand how tea influences CVD risk. Using data from 14 randomized controlled trials with a total of 798 study participants, we found no significant effects of tea consumption on blood pressure, cholesterol (total, LDL, and HDL), and triglyceride levels in both healthy adults and at-risk adults, such as those with obesity, prediabetes, borderline hypercholesterolemia, and metabolic syndrome. However, the 14 studies analyzed largely examined short-term tea consumption (4-24 weeks), suggesting that there is a need for larger, high-quality, longer-duration studies to truly understand the effects of tea on health.

Technical Abstract: Background: A recent systematic review of epidemiological evidence suggests that higher amounts of tea intake are associated with lower risks of cardiovascular disease (CVD) incidence and mortality. Objectives: Our study objective was to assess mechanisms by which tea consumption may influence CVD risks. Methods: A systematic review and meta-analysis was conducted to investigate the effects of green and/or black tea consumption (>=4 wk) on systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol, LDL cholesterol, HDL cholesterol, and triglyceride (TG) in healthy populations and among at-risk adults (analyzed separately) with metabolic syndrome, prediabetes, and hypercholesterolemia. The Grading of Recommendations Assessment, Development and Evaluation approach was used to rate the strength of evidence (SoE). Results: A total of 14 unique RCTs which randomly assigned 798 participants to either green tea, black tea, or placebo controls were included in our analyses. Intervention durations ranged from 4 to 24 wk (mean: 7.4 wk). Individual studies were judged as moderate to high quality based on risk of bias assessments. SoE was low to moderate owing to low sample sizes and insufficient power for most included studies to observe changes in the measured CVD biomarkers. Meta-analyses showed no significant effects of tea consumption on SBP, DBP, total cholesterol, LDL cholesterol, HDL cholesterol, and TG in healthy and at-risk adults (i.e., adults with obesity, prediabetes, borderline hypercholesterolemia, and metabolic syndrome). Conclusions: Short-term (4-24 wk) tea consumption does not appear to significantly affect blood pressure or lipids in healthy or at-risk adults, although the evidence is limited by insufficient power to detect changes in these CVD biomarkers. High-quality RCTs with longer durations and sufficient sample sizes are needed to fully elucidate the effects of tea.