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Table 1 Characteristic of the included studies

From: Does zinc with and without iron co-supplementation have effect on motor and mental development of children? A systematic review and meta-analysis

Study (year) Research design; location Participants Baseline length-for-age Z-score Intervention/Control groups Zinc dosageFrequency Zinc salt/Formulation Intervention duration Co-supplementation with Iron
Ashworth 1998 [32] Randomized Controlled Trial; Brazil Low birth weight term infants, low income families Length at birth:placebo:45.9 ± 1.47,1 mg zinc group:46.2 ± 1.22,5 mg zinc group:46.5 ± 1.24 1 mg Zinc (n = 68), 5 mg Zinc (n = 71)/Placebo (n = 66) 1 mg or 5 mg ZincDaily except Sundays Zinc sulfate/Syrup eight weeks from birth No
Bentley 1997 [33] Randomized Controlled Trial; Guatemala 6–9 months old infants N/A Zinc (n = 43)/Placebo (n = 42) 10 mg ZincDaily Zinc sulfate/ Syrup 7 months No
Black Baqui 2004 [22] Randomized Controlled Trial; Bangladesh 6 months old infants Zinc group:- 1.2 ± 0.8,Iron group:- 1.2 ± 0.8,Iron+ zinc group:- 1.2 ± 0.7,Placebo group:- 1.2 ± 0.9 Iron+ Zinc (n = 74)/Iron (n = 72),Zinc (n = 70)/ Placebo (n = 65) 20 mg Zinc/ 20 mg IronWeekly Zinc acetate/ Capsule 6 months Yes in two arms of trial
Black Sazawal 2004 [34] Randomized Controlled Trial; India One month old, SGA infants N/A (at 9 months old for zinc group: −1.8 ± 1.1, no zinc group: −2.0 ± 1.1) a micronutrient mix including riboflavin, calcium, phosphorus, folate, and iron with zinc sulfate (n = 100)/ the same micronutrient mix without zinc (n = 100) 5 mg Zinc/ 10 mg IronDaily Zinc sulfate/ Syrup 8 months Yes
Castillo-Durán 2001 [35] Randomized Controlled Trial; Chile 20 days old infants N/A (at 6 months old for zinc group: − 0.06 ± 0.74, placebo group: − 0.06 ± 0.75) Zinc (n = 75)/ placebo (n = 75) 5 mg ZincDaily Zinc sulfate/N/A 12 months No
Christian 2011 [36] Cluster Randomized Controlled Trial; Nepal 7–9 years old children height for age z score < − 2 (38.6–45.5%) M-IFA C-IFAZn (n = 217) /M-IFA C-IFA (n = 164)M-IFAZn C-IFAZn (n = 124)/ M-IFAZn C-IFA (n = 137) 10 mg zincDaily N/A/ Tablet To age 36 months old Yes
Colombo 2014 [37] Randomized Controlled Trial; Peru 6 months old infants Iron+copper+ zinc group:- 0.5 ± 0.9,Iron+copper group:- 0.6 ± 0.8 Iron + Copper + Zinc (n = 129) / Iron + Copper (122) 10 mg Zinc/10 mg ironDaily Zinc sulfate/Syrup 12 months Yes
Gardner 2005 [38] Randomized Controlled Trial; Jamaica 9–30 months old, underweight children Zinc groups:- 1.6 ± 0.82,Placebo groups:-1.25 ± 0.81 Zinc (n = 35)/zinc + stimulation (n = 26),placebo + stimulation (n = 23)/placebo (n = 42) 10 mg zincDaily Zinc sulfate/ Syrup 6 months No
Hamadani 2001 [39] Randomized Controlled Trial; Bangladesh less than 4 weeks old infants Zinc group:- 1.1 ± 0.9,Placebo group:- 1.1 ± 0.8 Zinc (n = 104)/ Placebo (n = 109) 5 mg ZincDaily Zinc acetate/ Syrup 5 months No
Heinig 2006 [40] Randomized Controlled Trial; United States of America 4 months old infants, fully breastfeed for ≥10 mo Length in 4 months of age:Zinc group:64.2 ± 2.4,Placebo group:63.9 ± 2.4 Zinc (n = 41)/placebo (n = 44) 5 mg zincDaily Zinc sulfate/Drop 182 days No
Jimenez 2007 [41] Randomized Controlled Trial; Cuba one month old infants, low birth weight N/A Zinc (n = 87)/ Placebo (n = 76) 10 mg ZincDaily – divided to two doses in the first 6 month of life Zinc sulfate/ Syrup 6 months No
Katz 2010 [42] Community-Based, Cluster Randomized, Placebo Controlled Trial; Nepal 1–35 months old children N/A Zinc (n = 759)/placebo (n = 847),Zinc + iron+ folic(n = 340) acid/iron+ folic acid (n = 242) 10 mg ZincDaily Zinc sulfate/ Dispersible tablet up to 36 months of age Yes in two arms of trial
Lind 2004 [43] Randomized Controlled Trial; Indonesia 6 months old infants, healthy singleton Iron group: - 0.28 ± 0.81,Zinc group: - 0.33 ± 0.84,Iron+ zinc group: - 0.36 ± 0.83,Placebo group: - 0.41 ± 0.96 Iron+ Zinc (n = 170)/Iron (n = 170),Zinc (n = 170)/ Placebo (n = 170) 10 mg Zinc/ 10 mg IronDaily Zinc sulfate/ Syrup 6 months Yes in two arms of trial
Locks 2016 [44] Randomized Controlled Trial; Tanzania 6 weeks old infants Zinc groups:-0.43 ± 1.23,No zinc groups: −0.25 ± 1.16 Zinc (n = 62)/Placebo (n = 66),Zinc+ Multivitamin (n = 59)/Multivitamin (n = 60) 5 mg Zinc for 6 week to 6 months and 10 mg for 7–18 monthsDaily Zinc sulfate/ Capsule From ages 6 weeks to 18 months No
Mathur 2015 [45] Randomized Controlled Trial; N/A Preterm neonates, Less than 7 days old, Exclusively breastfed during study period N/A Zinc (n = 50)/no placebo (n = 50) 2 mg/kg/ day Zinc gluconate/syrup untill 3 month of corrected age No
Murray-Kolb 2012 [46] Cluster Randomized Controlled Trial; Nepal 7–9 years old children Iron, folic acid and Zinc group:- 1.93 ± 0.87,Iron and folic acid group:- 1.85 ± 0.91,Zinc group: - 1.97 ± 0.84,Placebo group:- 1.89 ± 0.90 Iron +Folic acid+ Zinc (n = 209)/ Iron+ Folic acid (n = 178);Zinc (n = 160) /Placebo(n = 188) 10 mg zincDaily N/A/ Tablet 12 to 36 months of age Yes in two arms of trial
Olney 2006 [47] Community-Based, Randomized Controlled Trial; Tanzania (Pemba) 5–11 months old children Iron+folic acid group: - 1.5 ± 1.0,Zinc group:- 1.3 ± 1.0 in,Iron+folic acid+zinc group:- 1.4 ± 1.2,Placebo group: - 1.6 ± 1.0 Zinc (n = 218)/Placebo(n = 215),Zinc + Iron+ Folic acid (n = 220)/Iron+ Folic acid (n = 223) 5 mg ZincDaily N/A/ Dispersible tablet One year Yes in two arms of trial
Olney 2013 [23] Community-Based, Randomized Controlled Trial; Tanzania (Pemba) 5–9 and 10–14 months old children 26% stunted in 5–9 months of age children36% stunted in 10–14 months of age children Zinc/Placebo,Zinc + Iron+ Folic acid/Iron+ Folic acidTotal number = 528 10 mg Zinc more than 12 months of age and 5 mg Zinc in less than 12 months of age childrenDaily N/A/ Dispersible tablet One year Yes in two arms of trial
Pongcharoen 2011 [48] Randomized Controlled Trial; Thailand 9 years old children, breastfed at infancy baseline length for age z score in original article:Zinc: - 0.9 ± 0.9,Iron: - 0.9 ± 0.9,Iron+ zinc group:- 0.8 ± 0.9,Placebo group: - 0.8 ± 0.9 Zinc (n = 139)/Placebo (n = 139)Zinc + Iron (n = 135)/Iron (n = 147) 10 mg Zinc10 mg Ferrous sulfateDaily Zinc sulfate/Syrup 6 month Yes in two arms of trial
Prado 2016 [49] Cluster Randomized Controlled Trial; Burkina Faso 8.8 to 9.9 months of age LNS-Zn0 group: −1.18 ± 1.08,LNS-Zn10 group: −1.31 ± 1.12,LNS-TabZn5 group:-1.07 ± 1.09 LNS-Zn10(n = 326)/ LNS-Zn0(n = 328)LNS-TabZn5(n = 326)/ LNS-Zn0(n = 328) 10 mg with LNSDaily Zinc sulfate/ with LNS or tablet5 mg zinc in the form of tablet 9 months Yes (6 mg iron in LNS product)
Sazawal 1996 [50] Randomized Controlled Trial; India children 6 to 35 months N/A Zinc (n = 48)/Placebo (n = 45) 10 mg ZincDaily Zinc gluconate/ Syrup 1 to 6 months No
Siegel 2011 [51] Randomized Controlled Trial, Nepal aged 53 weeks or less children 22% stunted Zinc/placeboZinc + iron+ folic acid/iron+ folic acidTotal number = 259 5 mg zincDaily Zinc sulfate/ Dispersible tablets 0–37 weeks Yes in two arms of trial
Sudfeld 2019 [52] Randomized Controlled Trial; Tanzania 6 weeks old N/A Zinc (n = 101)/placebo (n = 92)Zinc and multivitamins (n = 66)/ multivitamins (n = 106) 5 mg zinc less than 6 months of age10 mg zinc more than 6 months of ageDaily Zinc/ Capsule 6 weeks to 18 months old NO
Surkan 2013 [53] Cluster Randomized Controlled Trial; Nepal 4–17 months old N/A Zinc (n = 127)/placebo (n = 152)Zinc + iron+ folic acid (n = 161)/iron+ folic acid (n = 129) 10 mg zincChildren less than one year old received 5 mg zincDaily Zinc sulfate/ Dispersible tablets One year Yes in two arms of trial
Taneja 2005 [54] Randomized Controlled Trial; India 12–18 months old infants 34.6% of zinc and 38.9% of placebo infants had length- for -age z -score less than −2 SD Zinc (n = 327) /Placebo (n = 323) 10 mg Zinc20 mg Zinc older childrenDaily Zinc gluconate/ Syrup 4 months No
  1. N/A the data is not available in the article
  2. M Mother, I Iron, F Folic acid, C Child, PL Placebo, Zn Zinc