Zinc is an essential mineral found in various foods your body needs for normal growth and good health. If you are in a high-risk group for a zinc deficiency, you may not be able to get all of the nutrient you need from your diet, and you'll need to take supplements. But you can also have too much of a good thing, as a zinc overdose can lead to a variety of health problems.
Identification
Good food sources of zinc include eggs, shellfish, beef and other red meats. Foods that are moderately high in the nutrient are nuts and legumes. Zinc is also found in whole-grain products and plant proteins, but it's less bioavailable due to phytic acid, a compound that inhibits zinc absorption. Supplements contain different forms of zinc, including zinc acetate, zinc gluconate, zinc picolinate and zinc sulfate, although research hasn't determined whether differences exist among the various forms in terms of their absorption, bioavailability or tolerability, according to the National Institutes of Health. Zinc supplements are available in tablets, capsules and in some zinc-containing cold lozenges.
History
Zinc is a trace element found in all forms of life, but its health effects weren't known until recently, when a clinical zinc deficiency in humans was first discovered in 1961. Since then, zinc insufficiency has been recognized as a problem, particularly in developing countries, the elderly and other high-risk groups.
Significance
Zinc is involved in many aspects of the metabolism of your body's cells. It's also needed as a catalyst for 100 enzymes to do their jobs; for a healthy immune system; for protein and DNA synthesis; wound healing; a proper sense of taste and smell; and for normal growth during pregnancy and childhood. As of 2010, zinc has been studied in at least 10 controlled trials for the treatment of common colds, with five studies finding zinc lozenges reduced the duration of the cold, according to the Linus Pauling Institute.
Considerations
The National Health and Nutrition Examination Survey discovered that most children and adults in the U.S. consume the recommended amounts of zinc in their diets, although 35 to 45 percent of adults 60 years and older have zinc intakes below the estimated average requirement. The daily recommended level for most adults is 11mg for men and 8mg for women, with strict vegetarians needing as much as 50 percent more zinc because high levels of phytic acid in plant foods reduce zinc absorption. Zinc supplements combined with foods like bran, whole-grain breads and cereals or phosphorus-containing foods such as milk or poultry may also prevent the zinc from being absorbed by your body.
Deficiencies
Certain high-risk groups are more likely to need zinc supplementation than other people. You may be in a high-risk group if you are pregnant or lactating; are receiving intravenous feedings; have a malnutrition disorder like anorexia nervosa; have gastrointestinal problems such as persistent diarrhea, celiac disease, short bowel syndrome, Crohn's disease or ulcerative colitis; or have cirrhosis or sickle cell anemia.
Warning
Zinc can cause problems if you take too high a dose. Signs of acute zinc toxicity include chest pain, dizziness, fainting, shortness of breath, yellow eyes or skin, abdominal pain, diarrhea and nausea. Single doses of 225 to 450mg of zinc can induce vomiting, while milder gastrointestinal distress has been reported at doses of 50 to 150mg per day of supplemental zinc. The major consequence of long-term consumption of excessive zinc is copper deficiency in your body, which can lead to the white blood cell disorder neutropenia, impaired bone calcification or hypochromic anemia.
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