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Table 4 Baseline and end-point mean 25(OH)D concentrations in vitamin D and placebo

From: Effects of vitamin D3 supplementation on serum 25(OH)D concentration and strength in athletes: a systematic review and meta-analysis of randomized controlled trials

Reference

Latitude

Vitamin D Daily Dosage (IU)

Weeks

Vitamin D Supplementationa

Placeboa

N

Pre

Post

Change

N

Pre

Post

Change

Insufficient vitamin D (N = 92)

         

Winter (N = 92)

         

 Jung 2018 [30]

< 45° N

5000

4

20

10.9 ± 0.5

38.4 ± 1.5

17.5

15

12.4 ± 0.8

13.1 ± 1.0

0.7

 Close 2013b [32]

≥45° N

5000

6

5

11.6 ± 10.0

41.3 ± 10.0

29.7

5

21.2 ± 11.6

29.6 ± 9.6

8.4

bClose 2013a [28]

≥45° N

5714

12

6

20.4 ± 10.4

36.5 ± 9.6

16.1

9^

20.8 ± 10.8

16.4 ± 8.8

−4.4

bClose 2013a [28]

≥45° N

2857

12

10

21.2 ± 10.4

34.1 ± 4.0

12.9

9^

20.8 ± 10.8

16.4 ± 8.8

− 4.4

 Wyon 2016 [29]

≥45° N

18,750

1

11

13.2 ± 3.8

16.8 ± 3.2

3.6

11

16.3 ± 2.7

16.3 ± 2.6

0

Sufficient vitamin D (N = 57)

         

Autumn (N = 57)

         

 Fairbairn 2018 [31]

≥45° S

3570

12

28

37.2 ± 7.6

44.4 ± 7.2

7.2

29

38 ± 6.8

34 ± 6.8

−4

  1. aPresented in ng/mL. bClose et al. compared multiple doses with one control group. ^ Indicates findings are from one study