Dr Berry talks about overdose at about minute 7. It is a fairly old video but one of the ones I watched some time ago.

https://www.youtube.com/watch?v=-FKS7C5BcbE&t=267s

Here is another one I watched a year or two ago.

https://www.youtube.com/watch?v=gjJdzHIwDDU

Thanks for making me think about my assumptions. Caused me to consider what I think I have learned.

There are some negative ones out there. But you have to look for them.

https://www.youtube.com/results?search_query=vitamin+d+research
 
Of course it is always up to the individual to decide who and what to believe. And some would foo-foo the idea of listening to on line doctors or researchers. But I have found what I consider a lot of good information from those on line sources (and also a lot of bunk). Separating the grain from the chaff, so to speak, is the problem.