this resolves my conflict over calcitriol vs cholecalciferol.
The entire NIH conference is geared towards exploiting the amazing anticancer properties of calcitriol and its analogues. Calcitriol promotes apoptosis (normal cell death) and forces normal cell differentiation, while inhibiting the blood supply and the spread of cancer cells. In short, calcitriol and its analogues should be ideal anticancer drugs. The problem is that intravenous calcitriol and its analogues cannot adequately get into the tissues without first causing hypercalcemia (high blood calcium). Plain old vitamin D does not have that problem because it does not cause hypercalcemia in dose below 20,000 units a day.
Instead, vitamin D is turned into 25(OH)D, which goes to the tissues where it is turned into calcitriol in direct proportion to blood levels of 25(OH)D. The real question is would all that extra tissue calcitriol help fight cancer? In fact, there is a growing consensus among research scientists that it would do just that. In the last few years, more and more cancer researchers are reporting that plain old cheap vitamin D may help fight cancer.