Zinc is one of the body's essential trace minerals. Although the body only needs small amounts of zinc, mild deficiency is not uncommon, according to the University of Maryland Medical Center. As with any other dietary supplement, zinc can cause unpleasant side effects when taken in high doses, so consult your doctor to determine the appropriate dosage for you.
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Adults ages 19 and older should limit their daily zinc intake to 40 mg per day unless their doctor recommends otherwise. This is the maximum dosage at which not side effects will occur, which is also known as the tolerable upper limit. The recommended daily intake for adult men is 11 mg per day, and 8 mg for adult women. Most American men get about 13 mg each day, while women generally get 9 mg daily, notes MedlinePlus.
Some health conditions warrant higher doses of zinc. Conditions like sickle cell anemia, anorexia nervosa, stomach ulcers, attention deficit-hyperactivity disorder and age-related macular degeneration might require doses as high as 220 mg per day. Only take these high doses under the supervision of your doctor. Some people also have higher daily zinc needs. For example, pregnant and lactating women have a higher recommended daily intake for zinc. Women need 11 mg of zinc during pregnancy, and 12 mg daily while breast-feeding.
Too much zinc can limit the absorption of copper, resulting in a copper deficiency. If you take a zinc supplement, your doctor might also recommend a copper supplement to prevent deficiency. According to the University of Maryland Medical Center, very high doses can decrease immunity, particularly in older adults, and increase the level of bad cholesterol in the blood. High zinc doses might also cause dizziness, fatigue, loss of muscle control, anemia, sweating, hallucinations and nausea.
As noted in the book "Nutrition," by Paul Insel and other authors, excessive zinc intake is most commonly associated with supplements. Unless your doctor recommends a supplement, try to get your daily needs for zinc from food sources. Good sources of zinc include oysters, red meat, poultry, cheese, shrimp and shellfish. Plant foods like legumes, whole grains, miso and tofu also contain zinc, although it is not as easily absorbed by the body when obtained from these foods.