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Table 7 Summary of results for iron, folate and calcium/vitamin D fortification in women

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

Iron fortification
Outcome/quality of evidence Combined effect Population Country Fortificant type Food vehicle
General/healthy population Deficient population Low- and lower middle-income countries Upper middle- and higher-income countries Ferrous sulfate NaFeEDTA Processed food Staples Condiments
Hemoglobin levels SMD: 0.62 (95% CI: 0.36, 0.89) SMD: 0.66 (95% CI: 0.30, 1.02) SMD: 0.59 (95% CI: 0.34, 0.83) SMD: 0.52 (95% CI: -0.12, 1.16) SMD: 0.66 (95% CI: 0.31, 1.00) SMD: 0.44 (95% CI: 0.21, 0.67) SMD: 0.48 (95% CI: 0.22, 0.73) SMD: 0.50 (95% CI: 0.30, 0.70) SMD: 0.90 (95% CI: -0.10, 1.90) SMD: 0.45 (95% CI: 0.22, 0.68)
Quality of evidence: Moderate   7 studies 2,819 participants 4 studies 404 participants 2 studies 524 participants 8 studies 2,588 participants 3 studies 310 participants 4 studies 1,588 participants 4 studies 398 participants 3 studies 1,211 participants 4 studies 1,614 participants
Serum ferritin levels SMD: 0.41 (95% CI: 0.23, 0.60) SMD: 0.23 (95% CI: 0.08, 0.38) SMD: 0.75 (95% CI: 0.47, 1.03) SMD: 0.48 (95% CI: 0.31, 0.66) SMD: 0.39 (95% CI: 0.17, 0.61) SMD: 0.42 (95% CI: 0.05, 0.78) SMD: 0.45 (95% CI: 0.21, 0.69) SMD: 0.46 (95% CI: 0.10, 0.82) SMD: 0.17 (95% CI: -0.15, 0.49) SMD: 0.50 (95% CI: 0.33, 0.68)
Quality of evidence: Low   6 studies 2,609 participants 4 studies 400 participants 2 studies 525 participants 8 studies 2,484 participants 1 study 117 participants 4 studies 1,559 participants 5 studies 1,390 participants to 2 studies 993 participants 3 studies 626 participants
Effect on anemia RR: 0.68 (95% CI: 0.49, 0.93) RR: 0.65 (95% CI: 0.40, 1.04) RR: 0.74 (95% CI: 0.61, 0.90) RR: 0.74 (95% CI: 0.61, 0.90) RR: 0.67 (95% CI: 0.39, 1.17) RR: 0.57 (95% CI: 0.34, 0.94) RR: 0.74 (95% CI: 0.61, 0.90) RR: 0.51 (95% CI: 0.21, 1.25) RR: 0.67 (95% CI: 0.39, 1.17) RR: 0.74 (95% CI: 0.61, 0.90)
Quality of evidence: Low   3 studies 1,180 participants 1 study 136 participants 1 study 136 participants 2 studies 1,056 participants 2 studies 199 participants 1 study 136 participants 1 study 124 participants 2 studies 1,056 participants 1 study 136 participants
Folate fortification
Outcome/quality of evidence Combined effect Quantity Duration
40 μg/100 g More than 100 μg/100 g Less than 1 year Greater than 1 year
Neural tube defects RR: 0.57 (95% CI: 0.45, 0.73) RR: 0.80 (95% CI: 0.75, 0.86) RR: 0.55 (95% CI: 0.41, 0.75) RR: 0.52 (95% CI: 0.28, 0.97) RR: 0.60 (95% CI: 0.50, 0.72)
Quality of evidence: Moderate   3 studies 2 studies 3 studies 4 studies
Spina bifida RR: 0.64 (95% CI: 0.57, 0.71) RR: 0.72 (95% CI: 0.65, 0.80) RR: 0.51 (95% CI: 0.41, 0.65) RR: 0.72 (95% CI: 0.65, 0.80) RR: 0.56 (95% CI: 0.49, 0.65)
Quality of evidence: Moderate   6 studies 3 studies 3 studies 7 studies
Anencephaly RR: 0.76 (95% CI: 0.68, 0.85) RR: 0.81 (95% CI: 0.74, 0.88) RR: 0.67 (95% CI: 0.43, 1.04) RR: 0.85 (95% CI: 0.79, 0.93) RR: 0.70 (95% CI: 0.59, 0.83)
Quality of evidence: Moderate   6 studies 2 studies 3 studies 7 studies
Serum folate levels SMD: 1.38 (95% CI: -0.20, 2.95) No studies identified No studies identified SMD: 1.65 (95% CI: -0.51, 3.82) SMD: 0.45 (95% CI: -0.06, 0.97)
Quality of evidence: Low     3 studies 2 studies
Iodine fortification
Outcome/quality of evidence Combined effect
Effect on hypothyroidism RR: 1.42 (95% CI: 1.11, 1.82)
Quality of evidence: Low 2 studies
Urinary iodine concentrations SMD: 7.16 (95% CI: 1.00, 13.31)
Quality of evidence: Moderate 4 studies
Calcium and vitamin D fortification
Outcome/quality of evidence Women of reproductive age Post-menopausal women
Vitamin D only Calcium and vitamin D Calcium only Vitamin D only
Serum parathyroid hormone levels SMD: 0.10 (95% CI: -0.28, 0.48) SMD: -0.23 (95% CI: -0.78, 0.32) No studies identified No studies identified
Quality of evidence: Low 2 studies 108 participants 1 study 52 participants   
Serum vitamin D levels SMD: 0.26 (95% CI: -0.22, 0.75) SMD: -2.50 (95% CI: -3.22, -1.78) SMD: 0.69 (95% CI: 0.38, 1.00) No studies identified
Quality of evidence: Moderate 1 study 66 participants 1 study 55 participants 3 studies 228  
  1. Estimates in BOLD show significant impacts. CI, confidence intervals; NaFeEDTA: sodium iron ethylenediaminetetraacetate; RR: relative risk; SMD: standard mean difference.