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.
odd sx? no dx? check w/ dietitian
DRI=MINIMUM eg bit.ly/1vgQclQ
99% don't meet these. meds/lifestyle can affect levels
status can be low in ms & other cond'ns
'but my results are normal'. typical panels don't test all
deficits occur in 'normal' range