Deva is deep into writing part 3 at the moment (the physicians husband here) where she reviews these trials, what they mean and how they should be interpreted. I think she will be finished soon.
That previous commentary on part 2 hasn't explored the larger statistical significant over time. Yes, it _can_ cause problems, but there is far more evidence to show deficiency, and far less evidence to show that even when taken at high levels there aren't many cases of problems, and those problems are not very severe.
Thank you thank you thank you. There is a craze for popping Vitamin D related to the raft of observational studies, here... so many of which never find a causal link.
Take my own particular condition: an inherited vascular dysplasia which causes frequent nose and GI bleeds. People with low Vitamin D seem to have a worse time of it in OBSERVATIONAL studies.
But people with GI bleeds so bad they have daily diarrhea from hemorrhages and anemia that disables them to the point they can't work aren't going to be out in the sun, and aren't going to be able to absorb as many vitamins in their gut due to the havoc the hemorrhaging is yielding.
Thinking really hard about the direction the arrow of causality runs here is massively important. Is it:
LOW VITAMIN D ---> BAD BLEEDING?
Or:
BAD BLEEDING ---> LOW VITAMIN D
And as the consequences of overdosing show, this isn't like popping an extra Metamucil cracker a day or something - dire stuff can happen.
Part 1: https://news.ycombinator.com/item?id=24138590
Part 2: https://news.ycombinator.com/item?id=24261948
To summarize - popping in large doses of Vitamin D is not exactly safe.