I found out that Vitamin D3 is actually not a vitamin per se, but a hormone!
Wikipedia has alot of great things to say about this important substance.
Scientists are finding that we need a lot more vitamin D3 than previously estimated. People are taking 4,6,8,10000 or more units daily. Some estimates indicate we make up to 20000 units when exposed to UVB rays from the sun for a 1/2 hour or more.
If you live in the north and/or don’t get much sun, you need to include this in your supplement portfolio.