Vitamin D is the new "it" supplement. We seem to be bouncing around the alphabet these decades. First it was the B vitamins in the early 90's, then Vitamin C, then E, then K and now Vitamin D.
This forum has been an invaluable resource lately so I thought I would share a few things:
1) I wouldn't take megadoses of this stuff. I have seen cases of hypervitaminosis D firsthand, and the last thing you want is high blood calcium and messed up kidneys from being a food fadist. If you are taking a lot of calcium for whatever reason - supplements, megadoses of tums, a poor understanding of your CKD meds - I would use even lower doses. If you have a history of any kind of granulomatous disease, I would just steer clear.
2) The amount of time it will take to get an ideal amount of vitamin D from the sun varies by your skin tone. A redhead may just need 10-15 minutes to get an ideal amount, whereas someone with darker skin may need an hour or longer. As a matter of fact, I wouldn't be surprised if the disease profile of darker skinned immigrants to places like North America and Europe is significantly worse than the local caucasian populations in coming generations (distinct from preexisting and significant socioeconomic variables).
3) There is some serious research going into vitamin D at the moment. Everything from multiple sclerosis to lymphoma as a matter of fact. For instance, there was a study that recently came out that showed poorer outcomes for patients with lymphoma and vitamin D deficiency - and this has been compelling enough that many north american docs are now giving generous doses - 2000 IU daily to patients with certain types of lymphoma as well. I am sure you can find the article on pubmed easily. Here is a link to a more accessible version of it:
http://www.webmd.com/cancer/non-hodgkins...a-survival
4) I don't know if there is any significant difference between long term outcomes with vitamin D taken orally and vitamin D obtained naturally through the sun...If anybody knows more about this, chip in sil vous plait.
Cheers.