22. Results of included systematic reviews: preschool and school‐aged children (aged 2 to 10 years).
| Review | Comparison | Outcome | Number of studies; number of participants | Results | GRADE assessment |
| Supplementation | |||||
|
Low 2013 Effects of daily iron supplementation in primary‐school‐aged children: systematic review and meta‐analysis of randomized controlled trials |
Iron supplementation versus placebo or control | Hb (g/L) | 28 trials; 6545 children | MD 8.38, 95% CI 6.21 to 10.56 (P < 0.001), significant increase in Hb concentration for children receiving iron supplementation | Not assessed |
| Anaemia | 7 trials; 1763 children | RR 0.50, 95% CI 0.39 to 0.64 (P < 0.001), significant reduction in anaemia for children receiving iron supplementation | Not assessed | ||
| IDA | 2 trials; 334 children | RR 0.12, 95% CI 0.02 to 0.66 (P = 0.01), significant reduction in IDA for children receiving iron supplementation | Not assessed | ||
| ID | 4 trials; 1020 children | RR 0.21, 95% CI 0.07 to 0.63 (P = 0.006), significant reduction in IDA for children receiving iron supplementation | Not assessed | ||
| Adverse event: 'gastrointestinal upset' | 4 trials; 576 children | RR 1.30, 95% CI 0.89 to 1.91, no evidence of a difference | Not assessed | ||
| Adverse event: 'constipation' | 2 trials; 202 children | RR 3.44, 95% CI 0.66 to 19.68, no evidence of a difference | Not assessed | ||
| Adverse event: 'vomiting' | 2 trials; 202 children | RR 0.86, 95% CI 0.13 to 5.67, no evidence of a difference | Not assessed | ||
|
De‐Regil 2011 Intermittent iron supplementation for improving nutrition and development in children under 12 years of age |
Intermittent supplementation with iron alone or with other nutrients versus placebo or no intervention | Hb (g/L) | 19 trials; 3032 children | MD 5.20, 95 % CI 2.51 to 7.88 (P < 0.001), significant increase in Hb concentration for children receiving intermittent iron supplementation versus placebo or no intervention | Low |
| Anaemia | 10 trials; 1824 children | RR 0.51, 95 % CI 0.37 to 0.72 (P < 0.001), significant reduction in anaemia for children receiving intermittent iron supplementation versus placebo or no intervention | Moderate | ||
| ID | 3 trials; 431 children | RR 0.24, 95 % CI 0.06 to 0.91 (P = 0.036), significant reduction in ID for children receiving intermittent iron supplementation versus placebo or no intervention | Very low | ||
| Any side effects | 1 trial; 53 children | RR 3.87, 95% CI 0.19 to 76.92, no evidence of a difference | Not assessed | ||
| Intermittent iron supplementation versus daily iron supplementation | Hb (g/L) | 19 trials; 2851 children | MD −0.60, 95% CI −1.54 to 0.35, no evidence of a difference | Low | |
| Anaemia | 6 trials; 980 children | RR 1.23, 95% CI 1.04 to 1.47 (P = 0.017), significant reduction in anaemia for children receiving intermittent iron supplementation versus daily iron | Low | ||
| ID | 1 trial; 76 children | RR 4.00, 95% CI 1.23 to 13.05, (P = 0.022), significant increase in ID for children receiving intermittent iron supplementation versus daily iron | Very low | ||
| Diarrhoea | 2 trials; 122 children | RR 1.17, 95% CI 0.60 to 2.28, no evidence of a difference | Not assessed | ||
| Any side effects | 4 trials; 895 children | RR 0.60, 95% CI 0.19 to 1.87, no evidence of a difference | Not assessed | ||
|
Mayo‐Wilson 2014a Zinc supplementation for preventing mortality, morbidity, and growth failure in children aged 6 months to 12 years of age |
Zinc versus no zinc | Blood Hb concentration | 26 trials; 6024 children | SMD 0.05, 95% CI ‐0.00 to 0.10, no evidence of a difference | Not assessed |
| Prevalence of anaemia | 13 trials; 4287 children | RR 1.00, 95% CI 0.95 to 1.06, no evidence of a difference | Not assessed | ||
| Prevalence of ID | 10 trials; 3149 children | RR 0.99, 95% CI 0.89 to 1.10, no evidence of a difference | Not assessed | ||
| Side effect: 'participants with ≥ 1 side effect' | 3 trials; 850 children | RR 1.13, 95% CI 1.00 to 1.27, no evidence of a difference | Not assessed | ||
| Side effect: 'vomiting episodes' | 5 trials; 4095 children | RR 1.68, 95% CI 1.61 to 1.75 (P < 0.001), significant increase in vomiting episodes for children receiving zinc supplementation | Not assessed | ||
| Side effect: 'participants with ≥ 1 vomiting episode' | 5 trials; 35192 children | RR 1.29, 95% CI 1.14 to 1.46 (P < 0.001), significant increase in ≥ 1 vomiting episode for children receiving zinc supplementation | High | ||
| Zinc versus zinc plus iron | Blood Hb concentration | 8 trials; 1341 children | SMD −0.23, 95% CI −0.34 to −0.12 (P < 0.001), difference favouring zinc plus iron | Not assessed | |
| Prevalence of anaemia | 3 trials; 482 children | RR 0.78, 95% CI 0.67 to 0.92 (P = 0.003), significant reduction anaemia prevalence for children receiving zinc plus iron | Not assessed | ||
| Prevalence of ID | 2 trials; 248 children | RR 0.12, 95% CI 0.04 to 0.32 (P < 0.001), reduction in ID prevalence for children receiving zinc plus iron | Not assessed | ||
|
Thompson 2013 Effects of daily iron supplementation in 2‐ to 5‐year‐old children: systematic review and meta‐analysis |
Iron supplementation versus control | Hb (g/L) | 9 trials; 1690 children | MD 6.97, 95% CI 4.21 to 9.72, significant increase in Hb concentration for children receiving iron supplementation | High |
| Anaemia | 1 trial; 359 children | 144/183 (79%) anaemic in iron group, 142/176 (81%) anaemic in control group; no evidence of a difference | Very low | ||
| Fortification | |||||
|
Aaron 2015 Multiple‐micronutrient fortified non‐dairy beverage interventions reduce the risk of anemia and iron deficiency in school‐aged children in low‐middle income countries: a systematic review and meta‐analysis |
Non‐dairy MMN‐fortified beverages versus control | Hb (g/L) | 8 trials; 3835 children | MD 2.76, 95% CI 1.19 to 4.33 (P = 0.004), significant increase in Hb concentration for children receiving MMN‐fortified beverages | Moderate |
| Anaemia | 6 trials; 2828 children | RR 0.63, 95% CI 0.54 to 0.73 (P < 0.001), significant reduction in anaemia for children receiving MMN‐fortified beverages | Moderate | ||
| ID | 7 trials; 2523 children | RR 0.32, 95% CI 0.23 to 0.45 (P < 0.001), significant reduction in ID for children receiving MMN‐fortified beverages | Moderate | ||
| IDA | 3 trials; 1649 children | RR 0.13, 95% CI 0.07 to 0.25 (P < 0.001), significant reduction in IDA for children receiving MMN‐fortified beverages | Low | ||
|
Das 2013a Systematic review of zinc fortification trials |
Zinc fortification versus control (with a regular diet or unfortified foods) | Serum Hb | 1 trial; 19 children | SMD 0.28, 95% CI −0.62 to 1.19, no evidence of a difference | Not assessed |
|
De‐Regil 2017 Point‐of‐use fortification of foods with micronutrient powders containing iron in children of preschool and school age |
Point‐of‐use fortification of foods with MNP versus no intervention or placebo | Hb (g/L) | 11 trials; 2746 children | MD 3.37, 95% CI 0.94 to 5.80 (P = 0.007), significant decrease in Hb concentration for children receiving MNP | Low |
| Anaemia | 10 trials; 2448 children | RR 0.66, 95% CI 0.49 to 0.88 (P = 0.005), significant decrease in anaemia for children receiving MNP | Moderate | ||
| IDA | 3 trials; 918 children | RR 0.28, 95% CI 0.07 to 1.10, no evidence of a difference | Not assessed | ||
| ID | 5 trials; 1364 children | RR 0.35, 95% CI 0.27 to 0.47, significant decrease in iron deficiency for children receiving MNP | Moderate | ||
| Adverse effects | 1 trial; 90 children | RR 1.09, 95% CI 0.16 to 7.42. no evidence of a difference | Moderate | ||
| Diarrhoea | 2 trials; 366 children | RR 0.97, 95% CI 0.53 to 1.78, no evidence of a difference | Low | ||
|
Eichler 2019 Health effects of micronutrient fortified dairy products and cereal food for children and adolescents: a systematic review |
Fortified dairy products and cereal food versus no fortification with MN | Hb g/L | 14 trials; 4855 children and adolescents | MD 0.90, 95% CI −0.10 to 1.80, no evidence of a difference | Very low |
| Anaemia | 12 trials; 1149 children | RR 0.87, 95% CI 0.76 to 1.01, no evidence of a difference | Very low | ||
| IDA | 5 trials; 148 children | RR 0.38, 95% CI 0.18 to 0.81, significant reduction in IDA for children receiving fortification | Very low | ||
| ID | 8 trials; 519 children | RR 0.62, 95% CI 0.40 to 0.97, significant reduction in ID for children receiving fortification | Very low | ||
| Adverse events | 3 trials | Three studies reported that no significant adverse events were related to the study food or to the fortification | Low | ||
CI: confidence interval; Hb: haemoglobin; ID: iron deficiency; IDA: iron deficiency anaemia; MD: mean difference; MMN: multiple‐micronutrient; MN: micronutrient; MNP: micronutrient powders; OR: odds ratio; RR: risk ratio; SMD: standardised mean difference.