Association between tea consumption and prevention of coronary artery disease: A systematic review and dose-response meta-analysis

Abstract

Background: Evidence from previous studies reporting on the relationship between tea consumption and its preventive effect on coronary artery disease (CAD) has conflicting outcomes. With the accumulation of new clinical evidence, we conducted this meta-analysis to assess tea consumption and CAD risk.

Methods: We searched PubMed, EMBASE, Cochrane Library, and Medline databases for published observational studies from their inception to May 2022. A random-effects model was used to calculate risk ratios with 95% confidence intervals. We also conducted linear and non-linear dose-response meta-analyses to analyze the association. We regarded that one cup equals 237 mL. Subgroup analyses and univariate meta-regression were conducted to explore the source of heterogeneity.

Results: A total of 35 studies, including 24 on green tea and 11 on black tea consumption, were included in this meta-analysis. An inverse association for the risk of CAD was observed for black tea (RR: 0.85; 95% CI: 0.76, 0.96) and green tea (RR: 0.93; 95% CI: 0.88, 0.99). The dose-response meta-analysis showed that drinking less than four cups of black tea daily may effectively prevent CAD, while more than 4-6 cups/d will promote disease risk. Furthermore, the dose-response relationship between green tea consumption and the prevention of CAD showed that the risk of CAD gradually decreased as green tea consumption increased. We also demonstrated that the more cups of green tea consumed, the lower the risk of CAD. In the subgroup analysis by continent, a significant negative correlation between CAD risk and green tea consumption was observed in the Asian population (RR: 0.92; 95% CI: 0.85, 0.99) but not in the western population [North America (RR: 0.97; 95% CI: 0.92, 1.03), Europe/Oceana (RR: 0.91; 95% CI: 0.78, 1.07)].

Conclusions: Higher green tea consumption was associated with reduced CAD risk, but drinking more than 4-6 cups of black tea per day may increase the risk. This study offers new insight into the relationship between tea consumption and its preventive effect on CAD. However, further large prospective cohort studies are needed to validate these findings.

Systematic review registration: The protocol of this systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) system (CRD42022348069).

Keywords: cardiovascular disease; coronary artery disease; dose-response; meta-analysis; tea.

Figure 1

Flow diagram of literature search and study selection.

Figure 2

Pie chart showing the results of the Newcastle-Ottawa Scale (NOS) scale.

Figure 3

Forest plot: Summary relative risks (RRs) of coronary artery disease (CAD) for comparing the highest black tea consumption with the lowest black tea consumption. The squares indicate study-specific risk estimates (the size of the square reflects the study's statistical weight), the horizontal lines indicate the 95% confidence intervals (CIs), and the diamond shows the summary RR estimate with its corresponding 95% CI.

Figure 4

Forest plot: results of subgroup analysis of black tea consumption and coronary artery disease (CAD) risk. (A) Forest plot of black tea consumption and CAD risk after subgroup analysis stratified by continent. (B) Forest plot of black tea consumption and CAD risk after subgroup analysis stratified by country.

Figure 5

Subgroup analysis of black tea intake and coronary artery disease (CAD) risk. (A) Forest plot of subgroup analysis stratified by the study design. (B) Forest plot of subgroup analysis stratified by gender.

Figure 6

Funnel plot and Egger's test analyses to detect publication bias of studies on black tea consumption and coronary artery disease (CAD) risk. (A) Funnel plot: used to detect the publication bias studies. (B) Egger chart: used to detect the publication bias of studies.

Figure 7

Dose-response relationship between black tea cup number (cups/d) and coronary artery disease (non-linear model).

Figure 8

Forest plot: Summary relative risks (RRs) of coronary artery disease for comparing the highest green tea consumption with the lowest green tea consumption. The squares indicate study-specific risk estimates (the size of the square reflects the study's statistical weight), the horizontal lines indicate the 95% confidence intervals (CIs), and the diamond shows the summary RR estimate with its corresponding 95% CI.

Figure 9

Forest plot: results of subgroup analysis of green tea consumption and coronary artery disease (CAD) risk. (A) Forest plot depicting green tea consumption and CAD risk after subgroup analysis stratified by continent. (B) Forest plot showing green tea consumption and CAD risk after subgroup analysis stratified based on country.

Figure 10

Forest plot depicting the subgroup analysis of green tea intake and coronary artery disease (CAD) risk. (A) Subgroup analysis forest plot stratified by the study design. (B) Forest plot of subgroup analysis based on gender.

Figure 11

Funnel plot and Egger's test analyses to detect publication bias of studies on green tea consumption and coronary artery disease (CAD) risk. (A) Funnel plot: used to detect studies on green tea consumption and CAD risk publication bias. (B) Egger chart: used to detect studies evaluating green tea consumption and CAD risk publication bias.

Figure 12

The dose-response relationship between green tea cup number (cups/d) and coronary artery disease (linear and non-linear models).