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Table 6 GRADE evidence profile for VitD food fortification for preventing vitD deficiency among children

From: The impact of vitamin D food fortification and health outcomes in children: a systematic review and meta-regression

Certainty assessment Summary of findings
No. of participants (studies)Follow-up Risk of bias Inconsistency Indirectness Imprecision Other considerations Overall certainty of evidence Number of children Relative effect (95% CI) Anticipated absolute effects
No. fortification Vitamin D fortification Risk with no fortification Risk difference with vitamin D fortification
25(OH)D concentration (follow-up: range 2 to 24 months; assessed with: nmol/L)
 4044 (18 RCTS) Not serious Seriousa, b Not serious Not serious Strong associationd High 1731 2313 The mean vitamin D concentration was 44 nmol/L MD 15.51 nmol/L higher (6.28 higher to 24.74 higher)
Vitamin D deficiency prevalence (follow up: range 2 to 24 months)
 4093 (16 RCTS) Not serious Seriousa Not serious Not serious Strong associationd High 739/1732 (42.7%)* 632/2361 (26.8%)* RR 0.53 (0.41 to 0.69) 427 per 1000 201 fewer per 1000 (252 to 132 fewer)
Cognitive function (follow up: range 6 to 14 months; assessed with: IQ)
 904 (2 RCTS) Seriousc Not serious Not serious Not serious Strong associatione OModerate 446 458  - MD 1.22 IQ points higher (0.65 higher to 1.79 higher)
School grade for Math (follow up: range 6 to 14 months)
 904 (2 RCTs) Seriousc Seriousa Not serious Serious None OOOVery LOW 446 458 SMD 0.90 SD higher (0.39 lower to 2.18 higher)
  1. The evidence quality table was produced using the online GRADE-Pro-Guidelines Development Tool (
  2. CI confidence interval, MD mean difference, RR risk ratio, SMD standardized mean difference
  3. aCI not overlapping
  4. bSubstantial heterogeneity was partially explained by a meta-regression model including vitD dose, latitude, and vitD baseline level. The proportion of total between-study variance explained by the model is 76.2%
  5. cWang et al. (lack of concealment, blinding, and did not use appropriate statistical method for cluster RCT)
  6. dLarge effect, dose response for every 100 IU vitD, the 25(OH)D concentration increased by 3 nmol/L when controlling for baseline 25(OH)D concentration and latitude
  7. eLarge effect: increased IQ by 1 point
  8. *Event rate high qulity evidence, O Moderate qulity evidence, OOO LOW qulity evidence, OOO Very LOW qulity evidence