Compared with placebo , vitamin D significantly increased 25-hydroxyvitamin D ( mean [ 95 % confidence interval ] in vitamin D group 20.1 [ 15.7 to 24.5 ] ng/mL at baseline and 65.7 [ 52.3 to 79.2 ] ng/mL at 12 weeks ; placebo 22.5 [ 18.1 to 26.8 ] ng/mL at baseline and 23.8 [ 10.4 to 37.2 ] ng/mL at 12 weeks ) .