Zinc is an essential trace element, which means that very small amounts are necessary for human health. However, getting too much zinc is dangerous and can even cause death. Even at doses that are safe for most people, zinc may cause dangerous interactions if taken with certain medications, including penicillamine. Dietary supplements providing zinc should only be taken under the supervision of a licensed health care provider.
Safe Use of Zinc
Although most people only need about 10 mg to 12 mg of zinc per day for health, therapeutic zinc doses of up to 40 mg per day are "likely safe," according to MedlinePlus. Nevertheless, routine zinc supplementation is not recommended unless prescribed by your doctor. Zinc supplements may be prescribed to treat zinc deficiency, which can occur due to severe diarrhea, liver cirrhosis and other health conditions. Zinc doses of up to 40 mg/day are also likely effective in treating diarrhea in malnourished children, according to MedlinePlus. In addition, zinc supplements may be used to treat low zinc levels associated with sickle cell disease, HIV, depression, male infertility and type 2 diabetes. However, even when used at "likely safe" doses, zinc may cause vomiting, diarrhea and other side effects, and it may interact with certain medications and other dietary supplements.
Hazards of High Zinc Doses
According to MedlinePlus, taking zinc in amounts higher than 40 mg/day is "likely unsafe" and can cause stomach pain, fatigue, fever, coughing and other problems. High doses of zinc may lower "good cholesterol" levels, raise "bad" cholesterol levels, weaken the immune system, upset magnesium balance and reduce copper absorption. Taking zinc supplements routinely for 10 or more years or taking more than 100 mg of zinc daily doubles the risk of developing prostate cancer, cautions MedlinePlus. Taking zinc in amounts of 450 mg or more can cause problems with blood iron, and single zinc doses of 10 to 30 g can be fatal.
Zinc Poisoning
Zinc poisoning is a serious condition that may occur from taking very high doses of zinc from dietary supplements. Zinc is also found in many industrial items such as paint, dyes, wood preservatives. If swallowed, industrial items containing zinc can also cause zinc poisoning, as can zinc fumes from heated or burning galvanized metal. With severe zinc poisoning, death may occur up to one week after the zinc exposure. Some symptoms of zinc poisoning include body pain, chills, cough, fever, convulsions, metallic taste in mouth, burning sensations, low blood pressure and shortness of breath. If zinc poisoning is suspected, it's important to seek immediate medical help and to give the poisoned person milk, unless otherwise instructed by a health care provider.
Dietary Sources
If you're concerned about getting enough dietary zinc, eating foods with zinc is a good way to obtain zinc without risking the numerous side effects associated with zinc supplements. Your body can absorb about 20 percent to 40 percent of the zinc present in foods, according to the University of Maryland Medical Center. The richest dietary sources of zinc are shellfish, red meats, poultry and cheese, particularly ricotta, Swiss and gouda. Certain plant foods also provide zinc, although zinc from animal sources such as meat and cheese is more readily absorbed by the body than plant sources of zinc, which include legumes, tofu, whole grains, green beans, cooked greens, mushrooms, sunflower seeds and others. Zinc from foods is also better absorbed when included in a meal that contains protein.
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