Table 1 Characteristics of 27 included randomized controlled trials
Reference | Study design | No. of subjects (M/F) | Country or Region | Age(y)a | BMI (kg/m2)a | FBG (mmol/) (GT/C) | FBI (μIU/ml) (GT/C) | HbA1c (%) (GT/C) | Duration | Tea group | Control group | Type of diet |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Basu 2011 [22] | P | 25(5/20) | USA | 42.5 ± 1.7 | 36.1 ± 1.3 | 5.0/4.9 | NA | 5.5/5.6 | 8wk | DGTE beverage (928 mg catechins) | Placebo (water) | Usual diet |
Bogdanski 2012 [23] | P | 56(28/28) | Poland | 30–60 | 33.2 ± 2.8 | 5.5/5.6 | 32.0/31.8 | NA | 3mo | GTE capsule (208 mg EGCG) | Placebo (cellulose) | Usual diet |
Brown 2009 [24] | P | 88(88/0) | UK | 40–65 | 31.2 ± 2.8 | 5.4/5.3 | 11.1/10.7 | 5.3/5.1 | 8wk | DGTE capsule (800 mg EGCG) | Placebo (lactose) | Usual diet |
Brown 2011 [25] | C | 66(66/0) | UK | 40–69 | 31.7 ± 2.7 | 5.9/6.0 | 12.5/12.1 | NA | 6wk | DGTE capsule (800 mg catechins) | Placebo (lactose) | Usual diet |
Chan 2006 [26] | P | 34(0/34) | China | 25–40 | 30.5 ± 1.9 | 5.1/5.2 | 7.3/13.8 | NA | 3mo | GTE capsule (661.3 mg cathchins, 152.8 mg caffeine) | Placebo | Usual diet, caffeine-free |
Chen 2016 | P | 77(0/77) | Taiwan | 44.5 ± 11.4 | 30.5 ± 3.7 | 5.5/5.9 | 19.6/16.5 | 5.8/6.2 | 12wk | DGTE capsule (1344 mg catechins) | Placebo (cellulose) | Usual diet |
Diepvens 2006 [28] | P | 46(0/46) | Netherlands | 19–57 | 27.7 ± 1.8 | 5.2/5.2 | NA | NA | 12wk | GTE capsule (1125 mg catechins, 225 mg caffeine) | Placebo | Low-energy diet |
Dostal 2016 | P | 237(0/237) | USA | 60.7 ± 5.0 | 28.2 ± 2.9 | 5.4/5.4 | 6.7/6.2 | NA | 12mo | DGTE capsule (1315 mg catechins) | Placebo (maltodextrin and cellulose) | Usual diet with exercise |
Frank 2009 [30] | P | 33(33/0) | UK | 18–55 | 26.7 ± 3.3 | 3.9/3.8 | NA | NA | 3wk | GTE capsule (672 mg catechins, 114 mg caffeine) | Placebo (matched with caffeine) | Usual diet with exercise, limit tea and coffee |
Fukino 2005 [31] | P | 66(53/13) | Japan | 53.5 ± 8.0 | 25.7 ± 4.3 | 7.5/7.8 | 8.7/10.3 | 6.2/6.1 | 2mo | GTE beverage (456 mg catechins, 102 mg caffeine) | Not report | Usual diet |
Fukino 2008 [32] | C | 60(49/11) | Japan | 32–73 | 25.5 ± 4.8 | 7.5/7.7 | 8.8/10.3 | 6.2/6.1 | 2mo | GTE beverage (456 mg catechins, 102 mg caffeine) | No intervention | Usual diet |
Hill 2007 [33] | P | 38(0/38) | Australia | 45–70 | 25–39.9 | 5.4/5.5 | 11.0/8.1 | NA | 12wk | DGTE capsule (300 mg EGCG) | Placebo (lactose capsules) | Usual diet with exercise |
Hsu 2008 [34] | P | 78(0/78) | Taiwan | 16–60 | > 27 | 6.3/5.8 | 16.1/13.1 | NA | 3mo | GTE capsule (613.5 mg cathchins, 27.3 mg caffeine) | Placebo | Usual diet |
Hsu 2011 [35] | P | 68(24/44) | Taiwan | 20–65 | > 25 | 9.5/9.7 | 14.5/11.4 | 8.4/8.4 | 16wk | DGTE capsule (1344 mg catechins) | Placebo (cellulose) | Usual diet |
Kovacs 2004 [36] | P | 104(26/78) | Netherlands | 18–60 | 25–35 | 5.7/5. | 11.0/10.3 | NA | 13w | GTE capsule (573 mg cathchins, 104 mg caffeine) | Placebo | Usual diet |
Liu 2014 [37] | P | 77(32/45) | Taiwan | 54.3 ± 6.8 | 26.3 ± 4.4 | 7.7/8.5 | 15.6/17.0 | 7.5/7.7 | 16wk | DGTE capsule (1344 mg catechins) | Placebo (cellulose) | Usual diet |
Lu 2016 [38] | P | 64(0/64) | Taiwan | 29.1 ± 8.9 | 21.2 ± 4.4 | 5.0/4.7 | NA | NA | 4wk | DGTE capsule (1344 mg catechins) | Placebo (cellulose) | Usual diet |
Mielgo-Ayuso 2014 [39] | P | 83(0/83) | Spain | 18–49 | 34 ± 2.8 | 5.0/5.1 | 9.6/8.4 | NA | 12wk | 300 mg EGCG | Placebo (lactose) | Usual diet |
Mirzaei 2009 [40] | P | 82(16/66) | Iran | 54.6 ± 11.2 | 29.9 ± 4.2 | 9.0/9.8 | 15.9/14.1 | 7.2/7.6 | 8w | GTE capsule (240 mg polyphenols, 150 mg caffeine) | Placebo (cellulose) | Usual diet |
Miyazaki 2013 [41] | P | 52(20/32) | Japan | 68.7 ± 6.3 | 22.6 ± 3.0 | 5.6/5.4 | NA | 5.5/5.1 | 14wk | GTE beverage (630.9 mg catechins, 77 mg caffeine) | GTE beverage (88.7 mg catechin, 82.4 mg caffeine) | Low-energy diet,limit exercise |
Nagao 2007 [42] | P | 240 (140/100) | Japan | 25–55 | 24–30 | 5.4/5.2 | NA | NA | 12wk | GTE beverage (582.8 mg catechins, 72.3 caffeine) | GTE beverage (96 mg catechins, matched with caffeine) | Usual diet with exercise |
Nagao 2009 [43] | P | 43(18/25) | Japan | 64.9 ± 7.3 | 25.6 ± 3.7 | 7.5/7.2 | 7.4/6.3 | 6.7/6.6 | 12wk | GTE beverage (582.8 mg catechins, 72.3 caffeine) | GTE beverage (96 mg catechins, matched with caffeine) | Usual diet |
Ryu 2006 [44] | C | 55(31/24) | Korea | 53.9 ± 7.7 | 25 ± 2.2 | 6.7/6.9 | 10.3/10.4 | NA | 4wk | GTE beverage (9 g green tea) | Placebo (water) | Usual diet |
Sone 2011 [45] | P | 51(18/33) | Japan | 20–70 | 25 ± 4 | 5.3/5.5 | NA | NA | 9wk | GTE beverage (400 mg catechins, 105 mg caffeine) | GTE beverage (100mgcatechins, 80 mg caffeine) | Usual diet, limit catechins |
Suliburska 2012 [46] | P | 46(23/23) | Poland | 30–60 | 32.8 ± 2.5 | 5.6/5.7 | NA | NA | 3mo | GTE capsule (208 mg EGCG) | Placebo (cellulose) | Usual diet |
Tadayon 2018 | P | 79(0/79) | Iran | 53.3 ± 3.9 | 29.9 ± 4.1 | 5.1/5.2 | NA | NA | 4wk | GTE capsule (80-94 mg polyphenol) | Placebo | Usual diet |
Wu-a 2012 [48] | P | 69(0/69) | USA | > 45 | 26.8–31.8 | 5.5/5.4 | 8.5/7.3 | 5.9/5.9 | 2mo | DGTE capsule (400 mg EGCG) | Placebo | Usual diet |
Wu-b 2012 [48] | P | 66(0/66) | USA | > 45 | 26.8–31.4 | 5.7/5.4 | 9.5/7.3 | 6.3/5.9 | 2mo | DGTE capsule (800 mg EGCG) | Placebo | Usual diet |