|Classification and external resources|
Zinc toxicity is a medical condition involving an overdose on, or toxic overexposure to, zinc. Such toxicity levels have been seen to occur at ingestion of greater than 225 mg of zinc. Excessive absorption of zinc can suppress copper and iron absorption. The free zinc ion in solution is highly toxic to bacteria, plants, invertebrates, and even vertebrate fish. Zinc is an essential trace metal with very low toxicity in humans.
Signs and symptoms
Following an oral intake of extremely high doses of zinc (where 300 mg Zn/d – 20 times the US RDA – is a "low intake" overdose), nausea, vomiting, pain, cramps and diarrhea may occur. There is evidence of induced copper deficiency, alterations of blood lipoprotein levels, increased levels of LDL, and decreased levels of HDL at long-term intakes of 100 mg Zn/d. The USDA RDA is 15 mg Zn/d.
There is also a condition called the "zinc shakes" or "zinc chills" or metal fume fever that can be induced by the inhalation of freshly formed zinc oxide formed during the welding of galvanized materials.
High levels of intake by humans
Zinc has been used therapeutically at a dose of 150 mg/day for months and in some cases for years, and in one case at a dose of up to 2000 mg/day zinc for months. A decrease in copper levels and hematological changes have been reported; however, those changes were completely reversed with the cessation of zinc intake.
However, zinc has been used as zinc gluconate and zinc acetate lozenges for treating the common cold and therefore the safety of usage at about 100 mg/day level is a relevant question. Thus, given that doses of over 150 mg/day for months to years has caused no permanent harm in many cases, a one week usage of about 100 mg/day of zinc in the form of lozenges would not be expected to cause serious or irreversible adverse health issues in most persons.
One study has shown zinc to be highly efficacious for curing warts; oral intake of zinc sulfate for two months at levels up to 600 mg/day was found to induce complete clearance of recalcitrant warts, with a success rate of 87%.
- Fosmire GJ (February 1990). "Zinc toxicity". Am. J. Clin. Nutr. 51 (2): 225–7. PMID 2407097.
- Rout, Gyana Ranjan; Das, Premananda (1 January 2003). "Effect of Metal Toxicity on Plant Growth and Metabolism: I. Zinc". Agronomie 23 (1): 3–11. doi:10.1051/agro:2002073.
- SMITH, SE; LARSON, EJ (April 1946). "Zinc toxicity in rats; antagonistic effects of copper and liver.". The Journal of biological chemistry 163: 29–38. PMID 21023625.
- Brita, T. A.; De Schamphelaere, Muyssen; Karel, A. C.; Janssen, Colin R. (2006). "Mechanisms of chronic waterborne Zn toxicity in Daphnia magna". Aquatic Toxicology 77 (4): 393–401. doi:10.1016/j.aquatox.2006.01.006. PMID 16472524.
- Ciubotariu D, Ghiciuc CM, Lupușoru CE (2015). "Zinc involvement in opioid addiction and analgesia - should zinc supplementation be recommended for opioid-treated persons?". Subst Abuse Treat Prev Policy 10 (1): 29. doi:10.1186/s13011-015-0025-2. PMC 4523930. PMID 26238243.
- Pettilä, V.; Takkunen, O.; Tukiainen, P. "Zinc chloride smoke inhalation: a rare cause of severe acute respiratory distress syndrome". Intensive Care Medicine 26 (2): 215–217. doi:10.1007/s001340050049.
- Pories, W.J. (1967). "Acceleration of healing with zinc sulfate". Ann Surg (165): 432–6. PMC 1617499. Retrieved October 31, 2015.
- Simkin, P.A. (1976). "Oral zinc sulphate in rheumatoid arthritis". Lancet (2): 539–42. PMID 60622. Retrieved October 31, 2015.
- Samman, S.; Roberts, D.C. (1987). "The effect of zinc supplements on plasma zinc and copper levels and the reported symptoms in healthy volunteers". Med J Aust (146): 246–9. PMID 3547053. Retrieved October 31, 2015.
- Forman, W.B. (1990). "Zinc abuse: an unsuspected cause of sideroblastic anemia". West J Med (152): 190–2. PMC 1002314. Retrieved October 31, 2015.
- Fiske, D.N. (1994). "Zinc-induced sideroblastic anemia: report of a case, review of the literature, and description of the hematologic syndrome". Am J Hematol (46): 147–50. PMID 8172183. Retrieved October 31, 2015.
- Hemilä, H. (2011). "Zinc lozenges may shorten the duration of colds: a systematic review". Open Respir Med J (5): 51–8. PMC 3136969. Archived from the original on October 31, 2015. Retrieved October 31, 2015.
- Al-Gurairi, F.T.; Al-Waiz, M. S. (2002). "Oral zinc sulphate in the treatment of recalcitrant viral warts: randomized placebo-controlled clinical trial". Br J Dermatol 146 (3): 423–31. PMID 11952542. Retrieved October 31, 2015.
- Lim KH, Riddell LJ, Nowson CA, Booth AO, Szymlek-Gay EA (2013). "Iron and zinc nutrition in the economically-developed world: a review". Nutrients 5 (8): 3184–211. doi:10.3390/nu5083184. PMC 3775249. PMID 23945676.
Homeostatic regulation of iron and zinc differ, with iron being regulated through absorption and zinc being regulated primarily through secretion. As the body does not have a means to eliminate excess iron, absorption from the small intestine is tightly regulated by hepcidin. Hepcidin is a peptide hormone that is present in higher concentrations when body iron is replete . Higher concentrations of hepcidin prevent ingested iron from entering the bloodstream by trapping iron in enterocytes which are naturally shed every two days , thereby preventing body iron from escalating to dangerous levels. In comparison, endogenous (pancreatic, biliary and intestinal) secretions comprise the main route of zinc loss, with larger zinc intakes being balanced by larger zinc secretions [113,114].