I've just taken a couple of zinc tablets so if the productiveness returns I might be onto something. I've been reading about it and apparently a lot of men are deficient which causes fatigue, bad sleep, insomnia, irritable moods, brain fog, all symptoms which I have. On a some forums I was reading a lot of the guys are taking pretty high doses and claiming great results from them. Standard dose is 10mg (100% of your RDA) and you don't seem to get anything higher in the shops here but these guys are taking anywhere up to 500mg a day which I think can be a bit risky. High doses of minerals can be bad for you. I'm testing out a couple a day at first to see what the effects are like, will up the dose later.