A few interesting notes here. First, it should not come as a big surprise that an intervention as simple, safe and inexpensive like Vit D would have a 20% reduced risk of fractures (which, by the way, is greater than that achieved by most medications). More importantly, it was easier for the researchers to determine the effect when supplementation was over 400 IU per day, meaning that we remain way off the mark by continuing the byline of 400 IU as the RDA.
Lastly, the benefit of Vit D was not dependent on calcium intake. It still frustrates me when patients come in and have been told to take a calcium supplement for the diagnosis of osteopenia or osteoporosis, but never any mention of increasing Vit D intake. Most of the research suggests that this recommendation should be the reverse!