Supplementing with vitamins and minerals is a tricky subject. The most recent scientific review recommends that healthy women NOT take calcium and vitamin D supplements to prevent bone fractures. BOTTOM LINE: No evidence for benefit, some health risk.
This article puts the latest recommendation in context with other scientific reviews: http://www.foodpolitics.com/2013/02/supplements-advice-about-calcium-and-vitamin-d-vs-osteoporosis/
“if an action or policy has a suspected risk of causing harm to the public or to the environment, in the absence of scientific consensus that the action or policy is harmful, the burden of proof that it is not harmful falls on those taking an act. This principle allows policy makers to make discretionary decisions in situations where there is the possibility of harm from taking a particular course or making a certain decision when extensive scientific knowledge on the matter is lacking. The principle implies that there is a social responsibility to protect the public from exposure to harm, when scientific investigation has found a plausible risk. These protections can be relaxed only if further scientific findings emerge that provide sound evidence that no harm will result.