Table 1 Characteristic of the included studies

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