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Table 2 Baseline characteristics of the included studies

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

Study Country County latitude Country income * Study Setting Total randomized patients, n Lost follow-up, n Intervention duration, months Treatment arm Vit D dose, IU/day Vit D isoform Added calcium, mg/day Age, years mean (SD) BMI, kg/m2; mean (SD) Baseline 25(OH)D concentration, nmol/L Outcomes
Akkermans et al. 2017[41] Western Europe Not clear High Clinical 325 91 5 MilkI 348** D3 110 1.7 (0.6) 0.3 (1.0)Z 69.4 (27.0) -Vit D concentration
-Vit D deficiency
-Compliance
MilkC 127 1.7 (0.6) 0.3 (1.1)Z 70.2 (26.7)
Battiprolu et al. 2006[51] India 17° Lower middle School 328 85 14 MilkI 400 400 10.8 (2.0) 15.2 (1.0) 74.0 (10.0) -Vit D concentration
-School performance
-School absences
-Compliance
MilkC 176 10.6 (2.0) 15.4 (1.2) 87.0 (15.0)
Benjeddou et al. 2019[57] Morocco 32° Lower middle School 239 39 9 MilkI 120 D3 240 7–9 15.4 (10) 53.04 (22.38) -Vit D concentration
-Vit D deficiency
MilkC # 60 240
Brett et al. 2016[52] Canada 45° High Clinical 77 3 3 Yogurt and cheeseI 400 D3 4.9 (2.1) 0.4 (0.6)Z 59.5 (13.0) -Vit D concentration
-Vit D deficiency
-Compliance
Yogurt and cheeseI 600 5.3 (2.0) 0.5 (0.9)Z 61.0 (10.6)
Yogurt and cheeseC # 140–195** 5.0 (1.8) 0.6 (1.0)Z 58.6 (14.4)
Brett 2018[58] Canada 45° High Daycare 51 2 6 Yogurt and cheeseI 300 D3 5 (1.8) 0.55 (0.98)Z 65.3 (12.2) -Vit D concentration
-Vit D deficiency
Yogurt and cheeseC # 167** 5.4 (2.0) 0.81 (0.88)Z 67.5 (15.1)
Du et al. 2004[49] China 39° Upper middle School 757 59 24 MilkI 133 D3 245 10.1 (0.3) 16.8 (2.6) 20.6 (8.8) -Vit D concentration
-Compliance
MilkC 245 10.1 (0.4) 17.1 (2.8) 17.7 (8.7)
No intervention D 10 (0.3) 16.8 (2.6) 19.1 (7.4)
Economos et al. 2014[42] USA 42° High Clinical 176 34 3 JuiceI 400 -– 1400 8.1 (1.5) 18.5 (4.2) 64.2 (92.8) -Vit D concentration
-Vit D deficiency
-Compliance
Juice+
Vit E+
Vit AI
400 1400 8.15 (1.4) 18.1 (4.0) 75.6 (27.2)
JuiceC -- 1400 7.9 (1.4) 18.5 (4.8) 64.3 (20.9)
Graham et al. 2009[46] New Zealand 37° High School 172 - 24 MilkI 60 D3 480 7.6 (0.9) -Vit D concentration
-Vit D deficiency
No milkC 7.2 (0.8)
Hettiarachchi et al. 2010[48] Sri Lanka Lower middle Clinical 60 0 9 CerealI 100 D3 450 4.0(0.6) 13.6 (1.2) 71.95 (32.3) -Vit D concentration
CerealC 0 4.1 (0.6) 13.6 (0.8) 103.4 (26.4)
Houghton et al. 2011[43] New Zealand 46° High Clinical 225 44 5 MilkI 252 132 1.4 52.8 (18.4) -Vit D concentration
-Vit D deficiency
Micronutrient fortified milk I 240 102 1.4   48.9 (22.4)
MeatC 1.4 48.8(18.6)
Hower et al. 2013[59] Germany 51° High Clinical 92 39 8 MilkI 392 105 3.8 (2.0–6.8)δ δ 15.6 53.7(26.5, 112.1) δ -Vit D concentration
-Vit D deficiency
-Compliance
-Infection rate
MilkC # 4.2 116 3.7 (2.0–6.2)δ δ 15.4 45.9(25.2, 107.3) δ
Khadgawat et al. 2013[53] India 28° Lower middle School 776 63 3 MilkI 600 D3 11.8 (1.1) 18.8 (3.7) 28.5 (13.1) -Vit D concentration
-Vit D deficiency
MilkI 1000 11.8 (1.1) 18.6 (3.5) 29.8 (14.0)
No interventionC 11.7 (1.1) 18.9 (3.3) 29.3 (13.0)
Kuriyan et al. 2016[54] India 13° Lower middle School 227 3 5 Malt- and cocoa-based milkI 116 492 8.1 (0.8) 53.9 (15.7) -Vit D concentration
-Vit D deficiency
-Ccognitive function
Malt- and cocoa-based milkC # 16 473 8.4 (0.9) 54.7 (17)
Madsen et al. 2013[60] Denmark 56° High Clinical 321 6 Bread and milkI 408** D3   4–17 72.8 -Vit D concentration
-Vit D deficiency
-Compliance
Bread and milkC # 88   4–17 72.8
Neyestani et al. 2014[50] Iran 35.6° Upper middle Clinical 146 13 3 MilkI 100 500 9–12 18.3 (0.4) 24.9 (1.4) -Vit D concentration
-Vit D deficiency
-Compliance
MilkC 240 18.3 (0.4) 27.4 (1.9)
170 7 3 Orange juice I 100 500 18.0 (0.3) 24.9 (1.3)
Orange juiceC   240 17.3 (0.3) 23.8 (1.1)
Ohlund et al. 2017[56] Sweden 63° High School and community 206 17 3 MilkI 400 D3 6.3 0.3Z 56 (52, 60)$ -Vit D concentration
-Vit D deficiency
MilkI 1000   6.3 0.3Z 58 (53, 62)$
MilkC # 80 6.3 − 0.1Z 49 (43, 55)$
Powers et al. 2016[55] UK 53° High Clinical 78 5 3 Cereal and milkI 166 215 18.8 (1.0) 22.7 (3.1) 42.9 (29.2) -Vit D concentration
-Vit D deficiency
-Compliance
Cereal and milkC # 8 215 19.0 (1.6) 21.9 (2.5) 39.4 (22.8)
Rich-Edwards et al. 2011[47] Mongolia 48° Lower middle School 278 2 Mongolian milkI 300 D3 10 (1.0) 17.0 (2.0) 20.0 (10.0) -Vit D concentration
-Vit D deficiency
-Compliance
-Infection rate
US milkI 300 10 (1.0) 17.0 (20) 24.9 (12.48)
MilkC 10 (1.0) 17.0 (20) 20.0 (10.0)
Sun 2011[45] China 43° Upper middle School 294 12 MilkI Not clear 6–8 46.2 (18.9) -Vit D concentration
No interventionC 6–8 45.2 (11.0)
Wang et al. 2017[44] China 34° Upper middle School 360 64 6 MilkI 150 100 13.2 (1.0) 21.2 (0.8) -Vit D deficiency
-School performance
MilkC 120 13.4 (0.9) 21.1 (0.7)
  1. BMI body mass index, SD standard deviation, Vit D, vitamin D
  2. *Gross national income (GNI) per capita, World Bank list of economies June 2017
  3. **Estimated average intake of vitamin D per/day
  4. IIntervention arm
  5. CControl arm
  6. DNot included in the analysis
  7. zz score
  8. $95th CI
  9. δMedian (IQR)
  10. δ δMedian (min, max)
  11. #vitD included in the control arms is the naturally occurring vitD in food