The Institute of Medicine report was issued at the beginning of 2011, which is over six years ago, not today as Dr. Lichtenfeld states. And there have been three clinical trials reported reduced incidence of cancer for those taking vitamin D + calcium.
In the Women's Health Initiative for the 15,646 women (43%) who were not taking personal calcium or vitamin D supplements at randomization, CaD (1 g Ca/400 IU vitamin D daily) significantly decreased the risk of total, breast, and invasive breast cancers by 14-20% and nonsignificantly reduced the risk of colorectal cancer by 17%. In women taking personal calcium or vitamin D supplements, CaD did not alter cancer risk (HR: 1.06-1.26). [Bolland, 2011].
The most recent clinical trial found a marginally insignificant reduced risk of cancer incidence for postmenopausal women taking 2000 IU/d vitamin D3 plus 1.5 g/d calcium, but a significantly reduced incidence rate for those with 25-hydroxyvitamin D [25(OH)D] concentrations >30 ng/mL compared to <30 ng/mL [Lappe, 2017].
There are many problems that plague vitamin D clinical trials. The most important one is that such trials are generally based on the guidelines for pharmaceutical drugs: 1 - the trial is the only source of the agent; and 2 - there is a linear dose-response relationship. Neither assumption is satisfied for vitamin D trials. In a recent analysis it was shown how to evaluate vitamin D clinical trials. In this analysis, the 25(OH)D concentration-incidence relationship for breast cancer based on case-control observational studies was used along with data from three CaD cancer trials. It was shown that the Lappe  trial was slightly under powered due to enrolling only 2300 women with baseline 25(OH)D concentration of 33 ng/mL (which is much higher than the mean population value of 25 ng/mL) and running the trial for four years [Grant, 2017].
When the totality of evidence including from geographical ecological studies with respect to solar UVB doses, the primary source of vitamin D, observational studies, clinical trials, and studies of mechanisms whereby vitamin D reduces risk of cancer incidence and increases survival, it has to be concluded that UVB exposure and vitamin D can greatly reduce the risk of cancer [Grant, 2017].
Bolland MJ, Grey A, Gamble GD, Reid IR. Calcium and vitamin D supplements and health outcomes: a reanalysis of the Women's Health Initiative (WHI) limited-access data set. Am J Clin Nutr. 2011 Oct;94(4):1144-9.
Grant WB. Roles of solar UVB and vitamin D in reducing cancer risk and increasing survival, Anticancer Res. 2016;36(3):1357-1370. http://ar.iiarjournals.org/content/36/3/1357.full.pdf+html
Grant WB, Boucher BJ. Randomized controlled trials of vitamin D and cancer incidence: A modeling study. PLos One. 2017 May 1;12(5):e0176448. https://doi.org/10.1371/journal.pone.0176448
Lappe J, Watson P, Travers-Gustafson D, Recker R, Garland C, Gorham E, Baggerly K, McDonnell SL. Effect of Vitamin D and Calcium Supplementation on Cancer Incidence in Older Women: A Randomized Clinical Trial. JAMA. 2017 Mar 28;317(12):1234-1243.
You must log in to use this feature, please click here to login.