USDA Recommended Dietary Allowance (RDA) for zinc is 11 mg/day for men and 8 mg/day for women. The recent median intake of this trace mineral from food in United States is approximately 14 mg/day for men and 11 mg/day for women. For an adult, FDA approved Tolerable Upper Intake Level (UL) of supplements of this trace mineral is 40 mg/day and consumption in excess of this level can pose certain risks.
Effects of zinc overdosegastrointestinal distress
The immediate acute effects of overdose of this trace mineral are metallic taste in the mouth, headache, epigastric pain, lack of appetite, nausea, vomiting, abdominal pain, diarrhea and related gastrointestinal distress.
Copper and iron metabolism
Zinc overdose suppresses copper and iron absorption and leads to nutritional deficiency of these trace minerals, anemia and neurological problems.
Overdose of 200-300 mg/day has been found to induce copper deficiency and connected neurological problems.
Prolonged use of its supplements ranging about 150 mg per day, apart from low copper status and decreased iron function, can result in red blood cell microcytosis, a type of anemia characterized by small red blood cells.
Neutropenia, a condition of an abnormally low number of neutrophils (white blood cells) may also result due to excess and overdose of the mineral.
Urinary and genital complications
In a trial on elderly men, an intake at 80 mg/day has shown increased urinary complications and hospitalizations.
Taking excess of this mineral in the form of supplements may cause its elevated levels in prostate gland and may increase the risk factors of enlarged prostrate gland or prostate cancer.
Zinc and medications
This mineral may interfere with the absorption of antibiotics like ciprofloxacin, enoxacin, ofloxacin, quinolone, trovafloxacin, sparfloxacin, tetracycline, demeclocycline and minocycline.
There is interaction in the gastrointestinal tract when both the mineral and antibiotic are taken together. and the absorption of both antibiotic and the mineral is inhibited. Differing the intake time of the supplement by at least 2-4 hours before or after the intake of antibiotic may solve the problem.
Similarly its overdose interferes with the absorption of rheumatoid arthritis drug, penicillamine, and spacing the intake time by at least two hours helps in the absorption of both.
Suppression of immune response, loss of smell sense, decrease in high-density lipoprotein (HDL) and renal failure are some of the adverse effects of chronic overdose with its supplements.
Channels to excess zinc levels
- Taking its supplements in excess of the recommended dosage,
- eating or drinking acidic food from zinc containers or containers galvanized with this metal,
- swallowing things made of its metallic form,
- inhaling freshly formed zinc oxide fumes,
- ingestion through overuse of denture adhesive creams,
- nasal sprays containing this trace mineral,
- Frequent use of cold lozenges containing the trace mineral,
- accidental consumption of topical products containing zinc,
- drinking well-water contaminated by zinc fertilizers,
- accumulation in patients with acute renal failure,
- haemochromatosis patients may accumulate excess zinc levels,