Emby,
I am sorry it took me so long to reply,but i was trying to find what are normal zinc levels or the reference ranges.
According to the ranges you mentioned and those i have your son's levels are low,infact pretty low,if you did plasma zinc levels,normal ranges are from 50-150 ug/dl,so you need to start him on some kind of zinc supplementation,i'll post the food resources of zinc in a while too,but supplementation will go along too.
Magnesium is necessary for heart's health and RBC's too,so look into it,i think you are in UK and Osteocare is available there,infact i think its manufactured there,it contains both zinc and magnesium along with calcium and vitamin D.
Andy,
Do you think osteocare will solve the problem or a bit more supplementation is needed?
Zaini.