TABLE 1.

Study characteristics and outcomes of those relevant intervention studies included in meta-analysis and systematic review¹

Study and country	Intervention, dose, and frequency	n	Sex and age	Follow-up	Results
Armas et al, 2004 (13); United States	1) No supplement (seasonal effect acting as control) 2) 1 tablet of 50,000 IU (1.25 mg) of vitamin D2 3) 10 tablets of 5000 IU (125 μg) of vitamin D3	30	All M20–61 y	28 d	28-d AUC was significantly greater for vitamin D3 supplementation group than vitamin D2 supplementation groups (P < 0.002).
Biancuzzo et al, 2010 (7); United States	1) Placebo capsule + placebo OJ 2) Placebo capsule + 1000 IU vitamin D3 OJ 3) Placebo capsule + 1000 IU vitamin D2 OJ 4) 1000 IU vitamin D3 capsule + placebo OJ 5) 1000 IU vitamin D2 capsule + placebo OJ	86	59 F27 M18–79 y	11 wk	No significant difference was shown in AUC for 25(OH)D when vitamins D2 and vitamin D3 were compared, irrespective of the intervention vehicle (capsule or juice).
Binkley et al, 2011 (15); United States	1) 1600 IU of vitamin D2/d	64	43 F	12 mo	Vitamin D3 was shown to be significantly more effective than vitamin D2 at raising serum 25(OH)D concentrations for the daily dosage (P = 0.05) and for daily and monthly dosage groups combined (P = 0.01). NS for monthly dosage group.
	2) 1600 IU of vitamin D3/d		21 M
	3) 50,000 IU of vitamin D2/mo		≥65 y
	4) 50,000 IU of vitamin D3/mo
Glendenning et al, 2009 (16); Australia	1) Ergocalciferol 1000 IU/d	70	Sex	3 mo	Vitamin D3 supplementation was associated with a 31% greater increase in concentrations of serum 25(OH)D than was vitamin D2 supplementation (P = 0.01).
	2) Cholecalciferol 1000 IU/d		Unknown
			82–84 y
Heaney et al, 2011 (17); United States	1) 1 capsule of 50,000 IU vitamin D2 2) 5 capsules of 10,000 IU vitamin D3	33	30 F3 M49.5 ± 9.8 y	12 wk	12-wk induced AUC was significantly greater for the vitamin D3 supplementation group than for the vitamin D2 group (P < 0.001). Vitamin D3 was calculated as 87% more potent at raising 25(OH)D.
Holick et al, 2008 (6); United States	1) Placebo	68	47 F	11 wk	At the end of the intervention, there was no significant difference in 25(OH)D concentrations between vitamin D2 and D3 groups.
	2) 1000 IU vitamin D2 capsule3) 1000 IU vitamin D3 capsule4) 500 IU D2 + 500 IU D3 capsule		21 M18–84 y
Leventis and Kiely 2009 (14); United Kingdom	Study 1: single intramuscular injection of 300,000 IU vitamin D2	69	Study 1: 43 F and 7 M	24 wk	Greater increases in serum 25(OH)D were achieved with vitamin D3 intervention
	Study 2: single 100-mL oral dose of 300,000 IU vitamin D3		Study 2: 15 F and 4 M
			23–82 y
Romagnoli et al, 2008 (5); Italy	1) Single oral dose of 300,000 IU vitamin D3 2) Single intramuscular dose of 300,000 IU vitamin D3 3) Single oral dose of 300,000 IU vitamin D2 4) Single intramuscular dose of 300,000 IU vitamin D2	32	All F66–97 y	60 d	Vitamin D3 significantly more potent at raising serum 25(OH)D concentrations than was vitamin D2 for both oral and intramuscular administration.
Tjellesen et al, 1986 (12); Denmark	1) 4000 IU vitamin D3 2) 4000 IU vitamin D2	19	All F22–49 y	8 wk	Vitamin D3 was linked to a greater increase in serum 25(OH)D compared with that in the vitamin D2 intervention group. No direct statistical comparison results were available.
Trang et al, 1998 (4); Canada	1) Untreated 2) 4000 IU vitamin D2 3) 4000 IU vitamin D3	89	48 F23 M18 Unknown38 ± 9 y	14 d	Greater increase in serum 25(OH)D concentrations with vitamin D3 group than with vitamin D2 group (P = 0.03).

¹OJ, orange juice; 25(OH)D, 25-hydroxyvitamin D.