. 2020 Apr 22;12(4):1163. doi: 10.3390/nu12041163

Table 2.

Characteristics of RCTs.

Author, Year	Study Design	Geographic Setting	Study Population	Age (Years) and Gender	Intervention	Duration	Daily Dose Equivalent	Control	Compliance
Al Daghri, 2019 [28]	Cluster RCT	Riyadh, Saudi Arabia	535 healthy children and adolescents with 25OHD < 50 nmol/L, non-hypertensive, not taking medications or vitamin supplements Mean BMI (SD) in kg/m²: Total: 23.0 (6.2); Tablet: 23.0 (6.2); Milk: 23.7 (5.6); C: 24.3 (6.4)	Range: 12-18 Mean (SD): Total: 14.9 (1.9) Tablet: 14.3 (1.6) Milk: 14.4 (1.5) C: 16.1 (1.9)	Tablet: n = 166; vitamin D tablet, 1000 IU daily	24 weeks	Tablet: 1000 IU Milk: 80 IU	n = 180; no intervention	Tablet: 91.1%Milk: 90.4% C: 86.7%
Al Daghri, 2019 [28]	Cluster RCT	Riyadh, Saudi Arabia		% Male: 45.4%	Milk: n = 189; 200 mL of vitamin D-fortified milk, 40 IU/100 mL, daily	24 weeks	Tablet: 1000 IU Milk: 80 IU	n = 180; no intervention	Tablet: 91.1%Milk: 90.4% C: 86.7%
Dong, 2010 [29]	Open-label, investigator-blinded RCT	Richmond, USA	44 healthy black (African American) adolescents, non-hypertensive, not taking medications or vitamin supplements Mean (SD) BMI percentile: I: 67.8 (30.9); C: 61.6 (33.4) (p = 0.53)	Range: 14–18 Mean (SD): Total: 16.3 (1.4) I: 16.5 (1.4)C: 16.3 (1.1) (p = 0.95)	n = 25; vitamin D3 (cholecalciferol), 2000 IU/day	16 weeks	2000 IU	n = 24; vitamin D3 (cholecalciferol); 400 IU/day	I: 85% C: 88% (p = 0.65)
Dong, 2010 [29]	Open-label, investigator-blinded RCT	Richmond, USA		% Male: 55.5%	n = 25; vitamin D3 (cholecalciferol), 2000 IU/day	16 weeks	2000 IU	n = 24; vitamin D3 (cholecalciferol); 400 IU/day	I: 85% C: 88% (p = 0.65)
Hauger, 2018 [21]	Double blind, placebo controlled RCT	Copenhagen, Denmark	119 healthy white children of European origin, not taking vitamin D supplement for ≥1 month prior to the study and not planning a winter sun vacation Normal weight: I1: 90%; I2: 92%; C: 66%	Range: 4–8 Mean (SD): Total: 6.7 (1.5) I1: 6.9 (1.5) I2: 6.7 (1.4) C: 6.5 (1.5)	I1: n = 44; 10 μg D3 tablet/day	20 weeks	I1: 400 IU I2: 800 IU	n = 43; placebo-matching tablet (0 μg D3/day)	I1: 97.6% I2: 97.6%
Hauger, 2018 [21]	Double blind, placebo controlled RCT	Copenhagen, Denmark		% Male: 36%	I2: n = 43; 20 μg D3 tablet/day	20 weeks	I1: 400 IU I2: 800 IU	n = 43; placebo-matching tablet (0 μg D3/day)	I1: 97.6% I2: 97.6%
Kelishadi, 2014 [30]	Triple blind, placebo controlled RCT	Isfahan, Iran	43 children and adolescents with metabolic syndrome and BMI ≥3 Z-scores, not taking medication or supplementation use, free of other chronic disease Mean BMI (SD) in kg/m²: C: 27.81(1.04); I: 28.08 (1.06)	Range 10–16	n = 21; 300,000 IU vitamin D3, 1 capsule/week	12 weeks	42,857 IU	n = 22; placebo-matching capsule	I: 88% C: 96% from original sample
Kelishadi, 2014 [30]	Triple blind, placebo controlled RCT	Isfahan, Iran		% Male: NR	n = 21; 300,000 IU vitamin D3, 1 capsule/week	12 weeks	42,857 IU	n = 22; placebo-matching capsule	I: 88% C: 96% from original sample
Smith, 2018 [31]	Double blind, placebo controlled RCT	United Kingdom	102 healthy white adolescents, not taking vitamin D supplement or planning a winter sun vacation Normal weight: I1: 80%; I2: 84%; C: 79%	Range: 14–18 Mean (SD): 15.9 (1.4) I1: 16.0 (1.4) I2: 15.9 (1.5) C: 15.9 (1.4)	I1: n = 39; 10 μg D3 tablet/day I2: n = 36; 20 μg D3 tablet/day	20 weeks	I1: 400 IU I2: 800 IU	C: n = 43; placebo- matching Tablet (0 μg D3/day)	I1: 94.2% I2: 94.4%
Smith, 2018 [31]	Double blind, placebo controlled RCT	United Kingdom		% Male: 43%		20 weeks	I1: 400 IU I2: 800 IU	C: n = 43; placebo- matching Tablet (0 μg D3/day)	I1: 94.2% I2: 94.4%

RCT: randomized controlled trial; 25OHD: 25-hydroxyvitamin D; BMI: body mass index; SD: standard deviation; C: control; IU: international units; I: intervention; NR: not reported.