RT Journal
A1 Malgarini R, Pimpinella G
T1 HIgh-dose oral vitamin d supplementation and risk of falls in older women
JF JAMA
JO JAMA
YR 2010
FD August 25
VO 304
IS 8
SP 854
OP 857
DO 10.1001/jama.2010.1168
UL http://dx.doi.org/10.1001/jama.2010.1168
AB 
Experimental data2 demonstrate that vitamin D3 in vitro promotes the differentiation of osteoclasts from monocyte macrophage stem cell precursors and at high doses increases in vivo osteoclastic bone resorption. This latter effect depends on vitamin D3 increasing the production in osteoblasts of RANKL (receptor activator for nuclear factor-κ B ligand), a key factor necessary for osteoclast differentiation and activation. This casts further doubt on the safety of high doses of vitamin D in patients at high risk of fractures and should be taken into account in the design of future studies.