http://www.insinc.com/onlinetv/directms13oct2005/softvnetplayer.htm The above is a very interesting lecture making the case that we need way more vitamin D than is officially recommended, ranting about the lack of publicity/money for studies, and relating it to a wide range of health problems--osteoporosis of course, but cancer, immune system goofups, autoimmune disease such as multiple sclerosis.
It is approximately an hour long. I just had it on while I was doing other things. Good stuff re: diabetes and insulin resistance at the very end. According to him, "play the odds". Nothing *bad* happens at 4000 iu per day and a lot good "could" happen.
Don't shoot the messenger. Just trying to give a quick summary for those that don't care to go to the trouble to listen to the whole thing. He lays out the evidence-- a lot of it, but he admits mostly circumstantial due to lack of funding for studies.