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Table 1 Characteristics of the included studies

From: Antioxidant effects of vitamins in type 2 diabetes: a meta-analysis of randomized controlled trials

Author, years Country Treatments N (sample) Duration (weeks) Main outcome measures Age (years) Male (%) Jadad score
Aghamohammadi, 2011 [25] Iran Vitamin B9 5 mg/day Placebo 70 8 MDA; TAC; vitamin concentration 58.7 ± 7.2 55.6 ± 9.3 100 3
Anderson, 2006 [26] Wales Vitamin C 1000 mg/day Placebo 20 6 TBARS 52.7 ± 6.9 53.6 ± 7.9 40.0 2
Antoniades, 2004 [27] Greece Vitamin C 2000 mg/day Placebo 17 4 Vitamin concentration; TNF 48.5 ± 6.6 52.6 ± 5.9 58.8 1
Ble-Castillo, 2005 [28] United States Vitamin E 800 IU/day Placebo 33 6 Blood glucose; HbA1c; MDA; GPx 51.3 ± 14.0 55.3 ± 11.6 0 2
Chen, 2006 [29] United States Vitamin C 800 mg/day Placebo 32 4 Blood glucose; vitamin concentration 50.0 ± 1.0 40.6 3
Dalan, 2016 [30] Singapore Vitamin D 4000 IU/day Vitamin D 2000 IU/day Placebo 64 16 HbA1c; vitamin concentration; GSH 52.2 ± 8.2 54.8 ± 10.8 51.6 5
Gariballa, 2013 [31] Arab Emirates Vitamin complex (B, C, E) Placebo 100 12 MDA; TNF; vitamin concentration 52 (44–56) 51 (42–60) 41.0 2
Haghighat, 2014 [32] Iran Vitamin E enriched canola oil 15 ml/day Placebo oil 45 8 CRP; NO 55.9 ± 5.9 55.2 ± 5.6 26.7 2
Hejazi, 2015 [33] Iran Vitamin E 400 IU/day Placebo 27 6 Blood glucose; MDA 48.0 ± 6.3 46.6 ± 7.6 26.0 3
Jamalan, 2015 [34] Iran Vitamin C 1000 mg/day Vitamin E 300 mg/day 80 4 Blood glucose; CRP; TNF 52.0 ± 8.0 100 2
Jorde, 2009 [35] Norway Vitamin D 40,000 IU/week Placebo 32 24 Blood glucose; HbA1c; vitamin concentration 57.7 ± 9.7 54.8 ± 5.9 56.2 2
Lai, 2008 [36] Japan Chromium 1000 µg Vitamin E 800 IU + chromium Placebo 30 24 Blood glucose; HbA1c; SOD; CAT; TBARS; TAS; GPx 53.2 ± 2.0 51.5 ± 1.7 50.5 ± 1.9 46.7 3
Lu, 2005 [37] Sweden Vitamin C 3000 mg/day Placebo 20 2 Blood glucose; HbA1c; IL-6 60.0 2
Mahmoudabadi, 2014 [38] Iran Eicosapentaenoic acid 500 mg/day Vitamin C 200 mg/day Vitamin C + eicosapentaenoic acid Placebo 81 8 Blood glucose; HbA1c; vitamin concentration; SOD; MDA; TAC; GPx 54.0 ± 5.0 53.0 ± 5.0 52.0 ± 6.0 50.0 ± 8.0 100 2
Manzella, 2001 [39] Italy Vitamin E 600 mg/day Placebo 50 16 HbA1c; TBARS 64.3 ± 4.7 65.1 ± 3.9 3
Mason, 2016 [40] Australia Vitamin C 1,000 mg/day Placebo 13 16 Insulin; GSH; IL-6 59.4 ± 3.5 92.3 3
Mazloom, 2011 [41] Iran Vitamin C 1,000 mg/day Placebo 27 6 Plasma lipid parameters; MDA 47.0 ± 8.9 46.6 ± 7.6 42.1 2
Mullan, 2002 [42] United Kingdom Vitamin C 500 mg/day Placebo 30 4 Plasma lipid parameters; LDL-ox 61.0 ± 6.5 57.9 ± 6.6 73.4 3
Nikooyeh, 2011/2014 [43, 44] Iran Yogurt (150 mg calcium/250 mL) Vitamin D fortified (150 mg calcium + 500 IU/250 mL) Vitamin D fortified (250 mg of calcium + 500 IU/250 mL) *Two bottles/day = 500 mL/day 90 12 Blood glucose; HbA1c; vitamin concentration; SOD; MDA 50.8 ± 6.6 51.4 ± 5.4 49.9 ± 6.2 38.9 2
Paolisso, 2000 [45] Italy Vitamin E 600 mg/day Placebo 40 8 TBARS; vitamin concentration 58.3 ± 6.4 56.7 ± 5.3 52.5 3
Park, 2002 [46] Korea Vitamin E 200 mg/day Placebo 98 8 Blood glucose; HbA1c; SOD; CAT 49.4 ± 9.3 49.5 ± 10.1 59.2 2
Reaven, 1995 [47] United States Vitamin E 1600 lU/day Placebo 21 10 Blood glucose; HbA1c; LDL-ox 60.8 ± 6.1 61.8 ± 8.4 100 2
Shab-Bidar, 2015 [48] Iran Vitamin D fortified Yogurt 500 UI, 500 ml/day Yogurt 100 12 Blood glucose; HbA1c; SOD; MDA; TAC; GSH 52.6 ± 6.3 52.4 ± 8.4 43.0 3
Sugden 2007 [49] United Kingdom Vitamin D 100,000 UI/day Placebo 34 8 HbA1c; vitamin concentration; NO 64.9 ± 10.3 63.5 ± 9.5 52.9 5
Tessier, 2009 [50] Canada Vitamin C 500 mg/day Vitamin C 1000 mg/day Placebo 36 12 Plasma lipid parameters; GSH 72.0 ± 5.0 72.0 ± 4.0 71.0 ± 4.0 22.2 3
Vafa, 2015 [51] Iran Vitamin E enriched canola oil 15 ml/day Canola oil 45 8 Blood glucose; MDA; TAC 55.9 ± 5.9 55.2 ± 5.6 73.3 4
Winterbone, 2007 [52] United Kingdom Vitamin E 1200 IU α-tocopherol/day Placebo 19 4 Blood glucose; insulin; vitamin concentration 62.7 ± 1.8 61.9 ± 1.9 100 2
Witham, 2010 [53] United Kingdom Vitamin D3 100,000 IU/day Vitamin D3 200,000 IU/day Placebo 41 16 HbA1c; vitamin concentration; GSH 65.3 ± 11.1 63.3 ± 9.6 66.7 ± 9.7 67.2 3
Wu, 2007 [54] Australia Vitamin E α-tocopherol 500 mg/day Vitamin E mixed tocopherols 500 mg/day Placebo 55 6 SOD; GPx 64.0 ± 7.0 58.0 ± 4.0 62.0 ± 7.0 74.5 2
Yiu, 2013 [55] China Vitamin D 500 IU/day Placebo 100 12 Blood glucose; HbA1c; SOD 65.8 ± 7.3 64.9 ± 8.9 50.0 4
  1. CAT catalase; CRP C-reactive protein; GPx glutathione peroxidase; GSH glutathione; HbA1c glycated hemoglobin; IL-6 interleukin; LDL-ox oxidized low-density lipoprotein; MDA malondialdehyde; NO nitric oxide; SOD superoxide dismutase; TAC total antioxidant capacity; TBARS thiobarbituric acid reactive substances; TNF tumor necrosis factor