I found this very interessting. To take 4000-8000 iu a day sounds high, but obviously its not. I take 1600 iu a day and that is considered very high here, but my D vitamin level was at 25, so not high, but according to these finding 1600 iu is acctually low.
I just wondere, for how long is it safe to take such a high dose as 4000-8000 iu? I know when D vitamins biuld up in the body its not safe at all and can be a health risk. My grandfather had too high D vitamin and ended up having surgery.