A new study shows that middle-aged adults who are taking the supplement didn't improve their bone density at all. The study used information from researchers at the University of Auckland, who analyzed 23 studies that took into account 4,082 adults. The researchers looked at bone strength and bone density measurements taken from five different places in the body.
At the end of their research, the authors of the study concluded that there isn't much evidence of vitamin D benefiting bone density. They also note that continuing to take vitamin D for adults who do not have vitamin D deficiencies, is no longer appropriate.
Medical News Today also points to a comment from Clifford J Rosen from the Maine Medical Research Institute that reinforces the findings in the study. Rosen mentions that taking vitamin D to prevent osteoporosis isn't necessary. However, he does mention that vitamin D couple with calcium can be effective in preventing hip fractures.
So vitamin D isn't totally useless, but it's just not helping to prevent bones from losing their density. Going forward, it will be interesting to see if a replacement vitamin or supplement is encouraged in place of vitamin D or what solution will be proposed, if there is one.