Annweiler and Beauchet suggest that the 20% nonvertebral fracture reduction with vitamin D supplementation at a dose greater than 400 IU/d may in part be explained by a direct benefit of vitamin D on muscle, resulting in fewer falls and thereby fewer fractures. The comment by Annweiler and Beauchet is supported by the presence of the vitamin D receptor in human muscle tissue1 and a rapid2,3 and sustained4- 7 effect of vitamin D supplementation on falls from several trials. Thus, we agree—although falls were not assessed in our meta-analysis,8 supplementation likely resulted in reduced falls contributing to the observed fracture risk reduction.
Bischoff-Ferrari HA, Willett WC, Wong JB, Stuck AE, Staehelin HB, Orav EJ, Thoma A, Kiel DP, Henschkowski J. Relationship Between Bone, Fracture, and Exercise: The Key Role of Vitamin D—Reply. Arch Intern Med. 2009;169(17):1633-1638. doi:10.1001/archinternmed.2009.323