Table 3.
Green tea consumption and metabolic health outcomes from meta-analyses.
| Outcome | Meta | Green tea | Results | Studies | Study design | Reference |
|---|---|---|---|---|---|---|
| Diabetes-related outcomes | 7 | 6 vs <1 cup/day | RR = 0.99 (0.97–1.24) | 2 | Cohort | [92] |
| Green tea/extract vs. placebo | Fasting plasma glucose: SMD = 0.04 (−0.15 to 0.24) | 7 | RCTs | [90] | ||
| Fasting serum insulin: SMD = −0.09 (0.30–0.11) | ||||||
| 2-h plasma glucose in the oral glucose tolerance test: SMD −0.14 (−0.63 to 0.34) | ||||||
| HbA1c: SMD = 0.10 (−0.13 to 0.33) | ||||||
| HOMA-IR: SMD = −0.06 (−0.35 to 0.23) | ||||||
| Green tea or green tea extract vs. placebo | HbA1c: SMD = −0.32 (−0.86 to 0.23) | 6 | RCTs | [89] | ||
| Insulin resistance SMD = −0.10 (−0.17 to 0.38) | ||||||
| Fasting insulin SMD = −0.25 (−0.64 to 0.15) | ||||||
| Fasting glucose SMD = −0.10 (−0.50 to 0.30) | ||||||
| Gtea vs. placebo/water | FBG: mean difference = −2.10 mg/dL (−3.93 to −0.27) | 11 | RCTs | [93] | ||
| Green tea | FBG: weighted mean difference: −0.09 mmol/L (−0.15, −0.03 mmol/L) | 17 | RCTs | [94] | ||
| HbA1c: weighted mean difference −0.30% (95% CI: −0.37, −0.22%) | ||||||
| Green tea | FBG: reduced levels in 1 of 3 small trials. | 3 | Human clinical trials | [95] | ||
| HbA1c: no change | ||||||
| Green tea or green tea extract | FBG: −0.07 (−0.60 to 0.47) | 8 | RCTs | [91] | ||
| FSI: 1.51 (0.05–2.97) | 6 | |||||
| HbA1c: −0.28 (−0.61 to 0.04) | 6 | |||||
| HOMA-IR: −0.00 (−0.68 to 0.68) | 5 | |||||
| BMI and fat | 7 | Green tea catechins | BMI: −0.55 (−0.65 to −0.40) | 15 | RCTs | [96] |
| Weight −1.38 kg (−1.70 to −1.06) | ||||||
| Daily green tea (EGCG 100 to 460 mg/day) | Body fat and body weight reduction periods of ≥12 weeks. caffeine doses between 80 and 300 mg/day has been shown to be an important factor | 15 | [97] | |||
| Catechins | Microcirc = −1.31 kg | 11 | Mixed | [99] | ||
| Green tea | No improvement in weight loss or maintenance | 2 | RCTs | [102] | ||
| Green tea preparations vs. control | Mean difference in weight loss of −0.04 kg (95% CI −0.5 to 0.4) non-Japanese | 14 | RCTs | [100] | ||
| Mean difference range −0.2 kg to −3.5 kg in Japanese | ||||||
| Green tea | Reduced weight −0.65 kg (−1.10 to −0.20) | 20 | RCTs | [101] | ||
| BMI −0.26 kg/m(2) (−0.43 to −0.10) | ||||||
| waist circumference −1.11 cm (−1.99 to −0.23) | ||||||
| Percent of body fat (PBF) (−1.42%, 95% CI: −3.02 to 0.18, P = 0.08) | ||||||
| Green tea catechin | Reduced total fat area: −17.7 cm2 (−20.9 to −14.4) | 6 | Human trials | [98] | ||
| Visceral fat area (−7.5 cm2, 95% CI: −9.3 to −5.7) | ||||||
| Subcutaneous fat area (−10.2 cm2, 95% CI: −12.5 to −7.8) | ||||||
| Blood pressure | 4 | Green tea | SBP: −2.08 mmHg (−3.06 to −1.05) | 13 | RCTs | [103] |
| DBP: −1.71 mmHg (−2.86, −0.56) | ||||||
| Green tea | SBP: 2.1 (− 2.9 to − 1.2) mmHg | 15 | RCTs | [104] | ||
| DBP: 1.7 (− 2.9 to − 0.5) | ||||||
| Green tea | SBP: MD: −1.94 mmHg (−2.95 to −0.93) | 20 | RCTs | [105] | ||
| Green tea vs control | SBP: −1.98 mmHg (−2.94 to −1.01 mmHg) | 13 | RCTs | [106] | ||
| DBP: −1.92 mmHg (−3.17 to −0.68 mmHg) |
BMI body mass index, DBP diastolic blood pressure, FBG fasting blood glucose, HbA1c glycosylated hemoglobin, HOMA-IR Homeostatic model assessment for insulin resistance, meta number of meta-analyses, RCTs randomized control trial, SBP systolic blood pressure, SMD standardized mean difference.