I'm talking about assaying the subjects' blood for prior and subsequent levels of the vitamin under test. Inasmuch as we have no way to tell whether they took the pills, we don't know whether the groups were properly randomized for their pre-intervention levels, diets, or effectiveness at metabolizing the supplement. It may even be the case that people with high CAC scores in the first place (the test population) already suffers from one or more of these problems across the board.

It isn't that hard to test people's blood, and yet the researchers prefer us to take it on faith that their sorting of control and intervention groups ironed all of this out? If I sound unreasonable, I don't apologize for it: public health decisions are important.