hi mrb, the short answer is, it's different for everyone.
bloodwork to get baseline info and monitoring over time would be ideal.
optimal daily supplemental intake depends on:
-baseline serum level (obviously ppl who are deficient need more)
-typical daily dietary intake (eg eating red meat or no?)
-individual zinc demand (for example people who eat gluten need more zinc to maintain healthy levels, smoke contains cadmium which is very similar to zinc and therefore interferes with absorption so smokers need more, and i don't know exactly how but alcohol drains a lot of nutrients and zinc is one of them).
you want your serum zinc level to be close to 18.2 umol/L and serum uric acid around 290-300 (i forget the units).
the 'best bet' recommendations for daily supplemental zinc are, if i recall correctly, on the order of 25-50mg per day.
READ ME key info on nutrient targets - www.thisisms.com/ftopict-2489.html
my approach: no meds so far - just nutrient-dense anti-inflammatory whole foods, and supplements where needed
info: www.whfoods.com, www.nutritiondata.com