Zinc is a trace mineral that plays an important role in body processes like regulating your immune system and healing wounds. According to the National Institutes of Health (NIH), most people in the United States get enough zinc from the foods they eat. Zinc is also available as an over-the-counter dietary supplement and is an ingredient in products sold as natural medicines for colds. Too much zinc can cause serious health problems.
Recommended Levels
The NIH lists recommended dietary allowances (RDA) for zinc by age and gender. RDA's start at 2 mg for male and female infants up to six months old and increase with age. Adult males 19 and older need 11 mg a day and adult females need 8 mg. Because of the risks associated with zinc overdose, the U.S. Food and Nutrition Board has established the upper limit for zinc intake at 40 mg a day for adults.
Acute Toxicity
Acute toxicity occurs when you consume a large amount of zinc at one time. For example, consuming contaminated food or beverages from improperly processed galvanized containers may cause a zinc overdose. The Linus Pauling Institute reports that a single dose of 225 to 450 mg of zinc will usually cause vomiting. Other symptoms include abdominal pain, diarrhea and nausea. Inhaling zinc oxide fumes may cause metal fume fever, causing rapid breathing, weakness and profuse sweating.
Chronic Toxicity
Chronic toxicity occurs when you consume high levels of zinc over a period of time. Taking from 150 to 450 mg of zinc a day may interfere with your immune system, reduce levels of the high-density lipoproteins known as "good cholesterol" and prevent your body from maintaining proper levels of copper and iron. The NIH notes that even a relatively moderate dose, 80 mg of zinc a day, is associated with urinary tract problems.
Interactions with Medications
Because zinc may interact with several types of medications, the NIH recommends that people taking medication should discuss their zinc intake with their health care provider. Most drugs that interact with zinc interfere with your system's ability to absorb the mineral, leading to a zinc deficiency. These include anticonvulsant drugs and diuretics. Taking zinc with the antibiotics tetracycline and quinolone, however, may decrease absorption of the antibiotic and reduce its effectiveness.
Other Problems
The American Cancer Society warns that information about drug interactions and other negative effects associated with zinc is incomplete. Zinc products, which are generally sold as dietary supplements, are not subject to the same Food and Drug Administration testing requirements as drugs. Users of zinc-based nasal gels and sprays that are sold as treatment for the common cold, for example, have reported long-lasting or permanent loss of the sense of smell.
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