Here is a snippit I didn't even get to fit in the Vitamin D Seminar - it shows the result from a properly executed RCT in the first couple of slides, then an outrageously poorly designed and controlled thingy that was published in 2007 also. More coverage was given to the crap RCT - surprise surprise. Engineers will like this: I've highlighted that the risible RCT still had some useful elements in the data, showing the beneficial effect even at ridiculously low supplementation levels of 400IU/day....needless to say this wasn't highlighted in the coverage of the paper. The painfully poor RCT conclusion? "Calcium and vitamin D supplementation did not reduce invasive breast cancer incidence in postmenopausal women. In addition, 25-hydroxyvitamin D levels were not associated with subsequent breast cancer risk. These findings do not support a relationship between total vitamin D intake and 25-hydroxyvitamin D levels with breast cancer risk" Yeah, sure they don't - because you, sirs, are infuriatingly incompetent.
A lecture explaining the proper RCT and stereotypical pushback is below - note that they started with pretty sufficient 29ng/ml 25(OH)D people - which was stacking the deck against themselves - imagine it had been 10ng/ml peeps and you gave them 5000 IU/day to get them up to 40ng/ml - more like it. I have no lecture to discuss the rubbish trial - maybe it's just as well.