Patients in this study who were given a zinc supplement developed a copper deficiency. They had a low plasma zinc concentration, but that doesn’t mean they were zinc deficient. You can have low zinc if your albumin levels are low (albumin is a zinc carrier) or you have a systemic inflammatory response, perhaps from surgery:
The Risk Of Copper Deficiency In Patients Prescribed Zinc Supplements, Journal of Clinical Pathology, 17 June 2015
This was an audit that occurred in Scotland. They said the RDA for zinc was 5.5–9.5 mg/day for men, 4–7 mg/day for women. Here it’s 11 mg for men, 8 mg for women. Not much, considering the average over-the-counter supplement contains 50 mg.
The dosages in this study ranged from 20 to 180 mg/day. The US Upper Limit for zinc is 40 mg/day.
The National Institutes of Health say this about taking too much zinc:
Intakes of 150–450 mg of zinc per day have been associated with such chronic effects as low copper status, altered iron function, reduced immune function, and reduced levels of high-density lipoproteins [HDLs] . Reductions in a copper-containing enzyme, a marker of copper status, have been reported with even moderately high zinc intakes of approximately 60 mg/day for up to 10 weeks . The doses of zinc used in the AREDS study (80 mg per day of zinc in the form of zinc oxide for 6.3 years, on average) have been associated with a significant increase in hospitalizations for genitourinary causes, raising the possibility that chronically high intakes of zinc adversely affect some aspects of urinary physiology .
The AREDS study tested a supplement that purportedly slows progression of macular degeneration. It’s a very popular supplement.
Inadequate copper leads to anemia, low white blood cell count, and nerve problems … numbness, tingling, poor balance, leg pain. It looks like taking an over-the-counter zinc supplement for just a few months may cause these symptoms.