I'm not Ron, but I also often wake up around 5 or 5:30 am, which is a pain, although I often do get back to sleep.
(My husband does too, although in his case it's stress related. He sleeps like a baby when he doesn't have to go to work the next day.... that period in the night seems to be acutely sensitive to adrenal state).
I take zinc now and again, having been really deficient in the not too distant past. Zinc definitely affects sleep quality with me, and it gives me weird vivid dreams if I take too much, which in my case is about 10mg or not very much at all. Before this I never had any dream recall for as long as I can remember. I prefer to get my zinc from red meat if possible, and these days that also gives me better sleep/dream recall.
I don't understand the mechanisms, but don't discount the zinc.