I found that as is so often the case Wikepedia answers most questions, as here on the subject of vitamin D. I take supplementation as Mrs D does except that as we get so much less sun in the UK and I go out much less now, I take 2000iu of D3 all through the summer as well. It would also seem that toxic levels are not that easy to reach short of deliberate or extremely careless overdosing

It is interesting to note the various cancers that appear less in those with higher levels of Vit D.

http://en.wikipedia.org/wiki/Vitamin_D

Tony