Table 1. Characteristics of the included studies.
| Study | Design | Participant | Age, yr | Intervention | Control | Treatment duration | Quality of reportinga |
|---|---|---|---|---|---|---|---|
| Fukino et al. (2008) [16] Japan |
Crossover | T2DM and pre-diabetes patients (n=60) |
32–73 | GTE beverage (456 mg catechins; 102 caffeine) | Water | 8 weeks | Moderate to high |
| Mirzaei et al. (2009) [27] Iran |
Parallel | T2DM patients (n=72) | 54.56±11.23 | GTE capsule (240 mg polyphenols; 150 mg caffeine) | Placebo (cellulose capsules) | 8 weeks | Low |
| Nagao et al. (2009) [30] Japan |
Parallel | T2DM patients (n=50) | 64.9±1.6 62.8±2.2 |
GTE beverage (528.8 mg catechins; 75 mg caffeine) | GTE beverage (96.3 mg catechins; 72.3 mg caffeine) | 12 weeks | Moderate to high |
| Huyen et al. (2010) [24] Vietnam |
Parallel | T2DM patients (n=24) | 63.5±6.5 57.2±8.2 |
Gynostemma pentaphyllum tea 6 g/day (3 g/packet, twice a day) | GT 6 g/day (3 g/packet, twice a day) | 12 weeks | High |
| Hsu et al. (2011) [17] China |
Parallel | T2DM patients (n=68) | 20-65 | DGTE capsule (856 mg EGCG) | Placebo (cellulose capsules) | 16 weeks | High |
| Huyen et al. (2013) [25] Vietnam |
Crossover | T2DM patients (n=16) | 58.8±5.9 58.1±6.6 |
Gynostemma pentaphyllum tea 6 g/day (3 g/packet, twice a day) | GT 6 g/day (3 g/packet, twice a day) | 8 weeks | Moderate to high |
| Mousavi et al. (2013) [28] Iran |
Parallel | T2DM patients (n=63) | 35–65 | GT (4 cups/day); GT (2 cups/day) | Water (no tea drinks) | 8 weeks | Moderate to high |
| Lasaite et al. (2014) [26] Lithuanian |
Parallel | T2DM patients (n=56) | 37–78 | GTE capsules (200 mg polyphenols) | Placebo (cellulose capsules) | 18 months | Low |
| Liu et al. (2014) [19] China | Parallel | T2DM patients (n=77) | 55.0±6.6 53.5±7.0 |
DGTE capsule (856.8 mg EGCG) | Placebo (cellulose capsules) | 16 weeks | High |
| Mozaffari-Khosravi et al. (2014) [29] Iran |
Parallel | T2DM patients (n=94) | 52.2±6.7 52.1±6.0 |
GT bag (3 g/day) | Sour tea bag (3 g/day) | 4 weeks | High |
| Ryu et al. (2006) [31] Korea |
Crossover | T2DM patients (n=55) | 53.9±7.7 | GTE beverage (9 g GT) | Water | 4 weeks | Very low |
Values are presented as range or mean±standard deviation.
T2DM, type 2 diabetes mellitus; GTE, green tea extract; GT, green tea; DGTE, decaffeinated green tea extract; EGCG, epigallocatechin gallate.
aAssessed by the CONSORT (CONsolidated Standards of Reporting Trials) checklist for randomized controlled trials.