Table 1. Characteristics of included studies.

1st author	Year	Country	Latitude	Administration route	Average daily dose (IU)	Follow-up time	n (vit D)	n (placebo)	n (total)	Primary endpoint	Healthy participants	Bacterial infection	Daily administration	Men	Women	Age (years)	25OH Vit D conc baseline (vit D) (nmol/L)	25OH Vit D conc follow-up (vit D) (nmol/L)	25OHVit D conc baseline (placebo) (nmol/L)	25OHVit D conc follow-up (placebo) (nmol/L)
Aloia [17]	2007	USA	42 N	oral	800/2000¤	3 y	104	104	208	No	Yes	No	Yes	0	1	60·6	46·9	86·9	43	43
Bergman [19]	2012	Sweden	59 N	oral	4000	12 mo	62	62	124	Yes	No	No	Yes	0·27	0·73	53·1	51·5	117·4	46·9	44
Camargo [21]	2012	Mongolia	48 N	oral	300	7 w	141	103	244	No	Yes	No	Yes	0·52	0·48	9·97	17·5	47·3	17	18
Jorde [23]	2012	Norway†	#	oral	3344	12 w	289	280	569	No	Yes	No		0·57	0·43	63	ND	ND	ND	ND
Laaksi [25]	2010	Finland	61 N	oral	400	6 mo	80	84	164	Yes	Yes	No	Yes	1	0	*	78·7	72	74·4	51
Lehouck [26]	2012	The Netherlands	50 N	oral	3333	12 mo	91	91	182	Yes	No	Yes	No (A)	0·8	0·2	68	50	130	50	55
Li-Ng [27]	2009	USA	41 N	oral	2000	3 mo	78	70	148	Yes	Yes	No	Yes	0·2	0·8	58·7	64·3	88·5	63	60·9
Majak [28]	2011	Poland	51 N	oral	500	6 mo	24	24	48	Yes	No	No	Yes	0·67	0·33	11·5	90	94	88	80
Manaseki-Holland [30]	2010	Afghanistan	33 N	oral	NA	3 mo	224	229	453	Yes	No	Yes	No (B)	0·56	0·44	1·2	ND	ND	ND	ND
Manaseki-Holland [29]	2012	Afghanistan	33 N	oral	1296	18 mo	1524	1522	3046	Yes	Yes	Yes	No (C)	0·52	0·48	0·8	ND	‡	ND	§
Murdoch [31]	2012	New Zealand	43 S	oral	3653	18 mo	161	161	322	Yes	Yes	No	No (D)	0·25	0·75	47·5	72·5	122·5	70	55
Urashima [32]	2010	Japan	40 N	oral	1200	4 mo	167	167	334	Yes	Yes	No	Yes	0·56	0·44	10·2	ND	ND	ND	ND

^*“young Finnish men”, “homogenous with regards to age”;

^†Norway, Denmark, Belgium, US, Austria, Scotland; #various latitudes;

^‡significantly higher than placebo;

^§significantly lower than vitamin D group, ¤800 IU/year for 2 years and 2000 IU/year during the 3rd year.

Administration interval: A, 100,000 IU/4 weeks; B, 100,000 once; C, 100,000 IU/3 months; D, 200,000 IU initially, 200,000 after 1 month and thereafter 100,000/month. The study by Lehouck et al (24) was not included in the meta-analysis, see Materials and Methods for details.