Once again a test bed of 300 people is hardly conclusive when the D cofactors are not considered. Those who get ample supplies of cofactors dont seem to suffer the calcium issue like those who do not get adequate cofactors.
Thats the problem with all these vitamin and mineral studies, there is such a complex interaction that looking at things with blinders on can give you data that may not accurately reflect whats really going on.
Of course not all tests are that narrow in focus but sadly most of them are. They are tossed out by the media with shocking headlines like "Too much Vitamin C can cause kidney stones!". People read the headline and jump to conclusions. Some may even goto the trouble of tracking down the article and reading the study itself and if they do so they will find that some people do have kidney issues when on high dose VC but then they leave it there and come to the same (false) conclusion that the vit C is bad and causes kidney stones.