Zinc is an essential micromineral that is required in the diet on daily basis. However, this mineral needs to be taken in very small amounts, 20 milligrams or less.
Other vital microminerals that humans need to acquire from food are boron, arsenic, copper, cobalt, fluorine, chromium, iron, iodine, molybdenum, manganese, silicon, nickel, and vanadium.
Although zinc is a vital requirement for having a healthy body, excessive intake is dangerous and may lead to zinc toxicity. Too much zinc absorption can cause iron and copper absorption to be suppressed. The free zinc ion is known to be highly toxic not only to plants but to vertebrate and invertebrate fishes as well. The Free Ion Activity Model (FIAM) shows that just micromolar amount of the said free ions can eventually harm and kill certain organisms.
The recommended dietary allowance (RDA) for zinc has been revised by the International Zinc Consultative Group (IZiNCG) in 2004. Their recommendations are the following:
|Toddlers 1 to 3 years||3 mg/day|
|Children 4 to 8 years||4 to 5 mg/day|
|Women||8 to 9 mg/day|
|Pregnant and lactating women||11 to 13 mg/day|
These recommendations are based on a standard reference body weight and take into account difference in diet.
Symptoms of zinc toxicity
Although zinc is one of the essential minerals in the body, too much consumption is not beneficial. Some of the common symptoms of zinc toxicity are fever, vomiting, nausea, fatigue, cough, diarrhea, dehydration and neuropathy.
Excessive zinc toxicity can lead to anemia, growth retardation, copper deficiency, altered iron function, decreased HDL (high density lipoprotein), increased Hemoglobin A1C, increased LDL (low density lipoprotein), and decreased immune function.
Because of the fact that zinc induces copper deficiency, studies are being conducted to examine the benefits of zinc on Wilson’s disease. Hepatolenticular degeneration or Wilson’s disease is an autosomal recessive genetic disorder wherein the tissues accumulate copper. This shows as psychiatric or neurological symptoms and liver disease. This disease is normally treated with medication that reduces the absorption of copper or the removal of the excess copper from the body.
Zinc Toxicity References And Further Reading
University of Maryland; American Journal of Clinical Nutrition; Creighton; Wikipedia; NIH.