According to the Office of Dietary Supplements, most American infants, children and adults consume the recommended amount of zinc each day. As a result, zinc deficiency is relatively uncommon. However, consuming too much zinc is possible with a diet rich in zinc and additional amounts consumed by supplements. Too much zinc can lead to poisoning or toxicity and can lead to uncomfortable symptoms. Treating zinc poisoning is important before the condition leads to permanent problems.
Zinc
Zinc is an essential mineral with several important functions, including immune function, wound healing, and normal growth and development during pregnancy. Zinc is not stored in the body and must be consumed daily to meet the body's requirements. The adult recommended dietary allowance for zinc is between 8 and 12 mg per day depending on gender and pregnancy status. Zinc can be found in oysters, beans, fortified cereals and dairy products. Zinc is also found in over-the-counter cold lozenges.
Acute Zinc Toxicity
Zinc poisoning or toxicity may occur rapidly. An acute incident may occur after an episode of food poisoning or accidentally consuming too much zinc in supplement form. The Office of Dietary Supplements reports that symptoms may appear as early as 30 minutes after ingesting 4,000 mg of zinc. These symptoms include nausea, vomiting, headaches, loss of appetite, diarrhea and stomach pain.
Chronic Zinc Toxicity
Chronic zinc poisoning or toxicity occurs after zinc is consumed in high amounts on a regular basis. The Office of Dietary Supplements reports, "Intakes of 150 to 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." Additional symptoms of chronic zinc poisoning include fever, chronic cough, low blood pressure, seizures, joint pain and a metallic taste in the mouth. Inhalation of zinc oxide during welding can lead to a condition called "zinc shakes" and can lead to neurological damage, according to the The Merck Manuals.
Zinc Toxicity and Copper Deficiency
The Office of Dietary Supplements reports that a moderately high intake of zinc, approximately 60 mg a day for up to 10 weeks, may be enough to alter copper levels in the body. Prolonged periods of zinc poisoning can cause an interference with copper metabolism and cause low blood copper levels. "The American Journal of Clinical Nutrition" reports that the same mechanism that causes copper levels to drop in relation to zinc toxicity may also lead to lower iron levels in the blood. A copper deficiency can cause anemia, weakness and numbness in the arms and legs, difficulty walking and loss of balance, and eventually permanent paralysis, according to MSNBC.com.
Zinc Toxicity in the News
In February 2010, a manufacturer of denture cream announced that it would remove zinc from its product after reports that long-term use causes neurological damage and blood problems in users. According to MSNBC.com, the manufacturer claims that its product is safe if used as directed, but if too much product is used, it may cause symptoms of zinc poisoning.
References
- Office of Dietary Supplements: Zinc
- "The American Journal of Clinical Nutrition"; Zinc Toxicity; Gary Fosmire; February 1990
- MSNBC.com; Glaxo Removes Zinc From Denture Cream; February 2010
- The Merck Manuals Online Medical Library; Zinc; Larry Johnson, M.D.; August 2008
- U.S. Mint: The Composition of the Cent
