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

Table 1 Characteristics of the included randomized controlled trials

Reference	Country	Latitude	Season	Sports Activity	Randomized (n = 163)	Intervention Vitamin D Dosage IU (μg)	Duration	Type	Product
Jung 2018 [30]	Korea	33.3° N	Winter	Taekwondo	22/22	5000	4 weeks	D₃ capsules	Bio-Tech Pharmacal, Inc. (Arkansas, USA)
Fairbairn 2018 [31]	New Zealand	45–46.5° S	Autumn	Rugby	28/29	3570 IU (89 μg)/day	11–12 weeks	D₃ tablets	Cal.D.Forte, PSM Healthcare, Auckland, New Zealand
Close 2013b [32]	UK	53° N	Winter	Soccer	5/5	5000(125)/day vs. PL	8 weeks	D₃ capsules	Biotech Pharmacal Inc., Phoenix, AZ, USA
Close 2013a [28]	UK	53° N	Winter	Football and Rugby	10/10/10	20,000 (500)/week vs. 40,000 (1000)/week vs. PL	12 weeks	D₃ capsules	Biotech Pharmacal Inc., Phoenix, AZ, USA
Wyon 2016 [29]	UK	52.3° N	Winter	Judo	11/11	150,000 (3750)/one time vs. PL	8 days	D₃ tablets	Not reported

Data are means unless stated otherwise; PL Placebo. 2013a, 30 football and rugby athletes were recruited in reference 28; 2013b, 10 soccer players were recruited in reference [32]

ISSN: 1550-2783