Zinc is an essential mineral that is needed by the human body to manufacture about 300 enzymes. Each of these enzymes have diverse processes and functions such as cell reproduction, immunity, protein synthesis, wound repair, vision, free radical protection and immunity.
Fortunately, a healthy daily diet can provide the zinc needs of most people. It is found in ordinary foods that such as red meat, sea foods and poultry. Oysters are excellent zinc sources. Other good sources include beans, whole grains, dairy products, cereals and nuts. However, zinc absorption is more effective from animal proteins than from plant sources.
The Recommended Dietary Allowance of zinc varies, but generally about 9-11 milligrams is enough for adults. However, the truth of the matter is that only about 30% of the zinc consumed can be absorbed by the human body. Many factors can interfere with zinc absorption such as phytates in your brain and fibers. Some people cannot absorb as much as they need, and may need to take zinc supplements in order to prevent zinc deficiency.
A zinc dose of 40 milligrams is approved safe to use by FDA and a zinc dosage more than this can pose certain risks. Excess zinc is dangerous. Too much zinc will likely interfere with the metabolism and absorption of other essential minerals in your body, most especially iron, magnesium and copper. Zinc side effects can become potentially serious at doses from 150 to 450 mg a day. Zinc intake in these ranges can decrease copper, iron and magnesium levels, reduce the body’s immune function, and reduce your HDL (good cholesterol) level.
Oral zinc sulfate supplements can also cause side effects such as stomach upset, heartburn and nausea. Rare side effects have also been reported and these include fever, sore throat, mouth sores, weakness and fatigue. It is very important to consult a doctor if you experience zinc side effects.
Zinc intake in excess of 300 mg per day has been reported to impair immune function. Some people report that zinc lozenges lead to stomach ache, nausea, mouth irritation, and a bad taste.
Zinc inhibits copper absorption. Copper deficiency can result in anemia, lower levels of HDL (“good”) cholesterol, cardiac arrhythmias and neuropathy. Copper intake should be increased if zinc supplementation continues for more than a few days (except for people with Wilson’s disease). Some sources recommend a 10:1 ratio of zinc to copper. Evidence suggests that no more that 2 mg of copper per day is needed to prevent zinc-induced copper deficiency. Many zinc supplements include copper in the formulation to prevent zinc-induced copper deficiency. Zinc-induced copper deficiency has been reported to cause reversible anemia and suppression of bone marrow.
A recent study suggests that excessive use of denture creams, such as Super-Poligrip and Fixodent, may cause copper deficiency, nerve damage and a serious nerve disorder called neuropathy. The study, which was published in the medical journal Neurology, was conducted by researchers at the University of Texas Southwestern Medical Center in Dallas and reported on four denture-wearing patients who developed nerve damage.
Marginal zinc deficiency may be a contributing factor in some cases of anemia. In a study of women with normocytic anemia (i.e., their red blood cells were of normal size) and low total iron-binding capacity (a blood test often used to assess the cause of anemia), combined iron and zinc supplementation significantly improved the anemia, whereas iron or zinc supplemented alone had only slight effects. Supplementation with zinc, or zinc and iron together, has been found to improve vitamin A status among children at high risk for deficiency of the three nutrients.
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