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Is zinc a miracle mineral?

March 16, 1999|By Lynn F. Little

It has been called the miracle mineral, touted as the answer to such diverse problems as the common cold, macular degeneration of the eye and infertility.

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Although zinc has been recognized as an essential nutrient in animals since the early 1900s, zinc deficiency was not recognized in humans until the 1960s, when it was determined to be the cause of poor growth and sexual development in certain groups of people in Egypt and Iran.

Zinc carries with it a bit of mysticism. A component of every living cell and essential for the activity of more than 200 enzymes, zinc helps manufacture the body's proteins and genetic materials. It is needed for growth and development, taste perception, hormonal activity and immune function.

There is good evidence that some of us, particularly women, young children and the elderly, are not getting enough zinc in our diets. The Recommended Dietary Allowance (RDA) for zinc is 15 milligrams for men, 12 milligrams for women and 10 milligrams for children. Studies continue to show that many women, young children and older persons consume only one-half to three-fourths the amount recommended daily.

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Taking too much zinc, however, has been shown to be as detrimental as not getting enough. Excessive zinc (more than 100 milligrams a day) can suppress immune function, just as too little zinc can. At high levels, zinc interferes with the metabolism of other minerals, including iron and copper.

Studies also have shown that zinc supplements at approximately three to five times the RDA may interfere with cholesterol metabolism, thereby increasing one's risk of heart disease. For these reasons, taking supplemental zinc at levels above the RDA should be done only under the advice of a doctor knowledgeable in nutrition.

The richest sources of zinc, as well as iron, are meats and seafood. Milk and milk products, though less rich in zinc, are important sources due to their wide availability and high consumption, especially among children.

Cereals and legumes contain significant amounts of zinc, but they also contain phytic acid and other substances that can interfere with the body's absorption of zinc. For most people, the best source of zinc is food, partially because most foods high in zinc also are high in other essential minerals.




Maryland Cooperative Extension programs are open to all citizens without regard to race, color, sex, disability, age, religion or national origin.

Lynn F. Little is a family and consumer sciences extension educator for Maryland Cooperative Extension, Washington County, University of Maryland.

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