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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

7°

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