LeBoff MS, Chou SH, Murata EM, et al. - Researchers sought to determine the effect of daily, vitamin D3 supplementation on bone mineral density (BMD) and/or structure. From VITAL, a double-blind, placebo-controlled RCT of supplemental vitamin D3 (2,000 IU/d) and/or omega-3 fatty acids (1 g/d) in 25,871 adults nationwide, they assessed a subcohort of 771 participants (men ≥ 50 and women ≥ 55 years; not taking bone active medications) at baseline and at 2-year follow-up (89% retention). As per outcomes, supplemental vitamin D3 vs placebo did not influence 2-year changes in aBMD at the spine, femoral neck, total hip, or whole body, or on measures of bone structure. A slight rise in spine aBMD and attenuation in loss of total hip aBMD was observed with vitamin D3 among participants with baseline free 25(OH)D (FVD) levels below the median (< 14.2 pmol/L). Further study is recommended to ascertain the value of baseline FVD levels in the identification of those who are more likely to benefit from supplementation.