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Table 5 Summary of results for iodine, Vitamin A and calcium/vitamin D fortification in children

From: Micronutrient fortification of food and its impact on woman and child health: a systematic review

   Iodine fortification
Outcome/quality of evidence Combined effect  
Serum thyroxin levels SMD: 0.45 (95% CI: -1.15, 2.06) 2 studies 1,131 participants reported this outcome. The studies were conducted in Africa on school-going children.
Quality of evidence: Low  
Urinary iodine concentrations SMD: 6.39 (95% CI: 2.69, 10.08) 2 studies 1,016 participants reported this outcome. The studies were conducted in Africa on school-going children.
Quality of evidence: Moderate  
   Vitamin A fortification
Outcome/quality of evidence Combined effect  
Hemoglobin levels SMD: 0.48 (95% CI: 0.07, 0.89) 2 studies with1,538 participants reported the outcome. The study by Zhang et al.[132] used four different comparison groups. The first group received low amounts of vitamin A-fortified biscuits for 9 months daily. The second group received high amount of vitamin A-fortified biscuits for 3 months daily. The third group received very high amounts of vitamin A-fortified biscuits for 3 months weekly. The standard mean differences for the three groups were 0.73 (95% CI: 0.42, 1.04), 0.62 (95% CI: 0.38, 0.85) and 0.63 (95% CI: 0.38, 0.88) respectively.
Quality of evidence: Low
Serum vitamin A concentration SMD: 0.61 (95% CI: 0.39, 0.83) 3 studies with 2,362 participants reported the outcome. The study by Zhang et al.[132] used four different comparison groups as explained in comments for hemoglobin levels. The standard mean differences for the three groups were 0.52 (95% CI: 0.21, 0.82), 0.73 (95% CI: 0.49, 0.97) and 0.44 (95% CI: 0.22, 0.66).
Quality of evidence: Low
Vitamin A deficiency RR: 0.39 (95% CI: 0.09, 1.74) 2 studies with 1,465 participants reported the outcome. The study by Zhang et al.[132] showed positive impacts in reducing vitamin A deficiency whereas the study by Solon et al.[110] showed negative impacts. The latter used monosodium glutamate for vitamin A fortification and the quantity of vitamin A used was much less than that used by Zhang et al.
Quality of evidence: Moderate
Calcium and vitamin D fortification
Outcome/quality of evidence Combined effect Calcium only Vitamin D only Calcium and vitamin D
Serum parathyroid hormone levels SMD: -0.40 (95% CI: -0.56, -0.24) SMD: -0.28 (95% CI: -0.50, -0.06) No studies identified SMD: -0.52 (95% CI: -0.74, -0.29)
Quality of evidence: Low 2 studies 317 participants 2 studies 327 participants
Serum vitamin D levels SMD: 1.23 (95% CI: 0.35, 2.11) SMD: -0.15 (95% CI: -0.41, 0.10) SMD: 1.76 (95% CI: 0.37, 3.15) SMD: 1.58 (95% CI: 1.28, 1.87)
Quality of evidence: Moderate 1 study 233 participants 2 studies 651 participants 1 study 235 participants
Serum calcium levels SMD: -0.40 (95% CI: -0.59, -0.20) SMD: -0.30 (95% CI: -0.56, -0.04) No studies identified SMD: -0.50 (95% CI: -0.76, -0.24)
Quality of evidence: Low 1 study 231 participants   1 study 235 participants
  1. Estimates in bold show significant impacts. CI, confidence intervals; RR: relative risk; SMD: standard mean difference.