Zinc naturally occurs in some foods, is added to others, and available as a single or combination dietary supplements.
Many foods have zinc that is available for immediate use to satisfy the steady state requirement of the body. (Institute of Medicine, Food and Nutrition Board, 2001) (U.S. Department of Agriculture, 2011). These include:
- Oysters have more zinc than any other food, but red meat and poultry are the major sources of zinc in the U.S. diet.
- Seafood such as crab and lobster
- Whole grains
- Fortified breakfast cereals
- Dairy products
Zinc in the Body
The body uses zinc in many parts of cellular metabolism, including the following:
- It is needed to cause or accelerate chemical changes in about 100 enzymes. (HH., 1994) (Institute of Medicine, Food and Nutrition Board, 2001).
- It contributes to immune function. (NW, 1998), (AS, 1995)
- It aids in protein synthesis. (AS, 1995)
- It is known to aid in wound healing. (CA, 1996)
- DNA synthesis is aided by zinc. (Institute of Medicine, Food and Nutrition Board, 2001) (AS, 1995)
- Zinc also helps the body’s cells divide properly. (AS, 1995)
- Without zinc, normal growth and development of the human body during pregnancy, childhood and adolescence would be impossible. (Simmer K, 1985) (Maret W, 2006)
- It helps people smell and taste properly. (Prasad AS, 1997)
People need to take zinc every day, in either food or supplements, to maintain a steady state since the body has no ability to store the mineral. (Rink L, 2000) Zinc is also sold as a help to counteract cold symptoms in some over-the-counter drugs.
Binding Factors & Bio-availability
Phytates, found in certain whole-grain breads, cereals and other foods, bind with zinc and inhibit its absorption (Institute of Medicine, Food and Nutrition Board, 2001). This means that the zinc that is available from plants is less usable than that from meats.
Recommended Daily Intake of Zinc
The recommended daily intake of zinc has been provided in the Dietary Reference Intakes, which were determined, by the Food and Nutrition Board at the Institute of Medicine of the National Academies.
The Recommended Daily Allowance (RDA) is determined to be the average daily level of intake that is enough to meet the requirements of from 97 to 98 percent of healthy persons. The current RDA ranges from 2 mg for infants of less than six months to 12 mg for lactating adult women. (Institute of Medicine, Food and Nutrition Board, 2001) Tolerable Upper Intake Level (UL) is the maximum daily intake that will probably not have adverse effects. (Institute of Medicine, Food and Nutrition Board, 2001)
Who Needs Zinc Supplements?
Zinc supplements are usually taken by populations that are demonstrated to need extra zinc outside their daily diets. Those populations include:
Babies older than 6 months who are exclusively breast-fed. Alcoholics Sickle Cell disease patients Vegetarians Pregnant and lactating women Those wishing to boost their immune system, especially to fight off colds and flu
Dangers of Overuse of Zinc Supplements
Even though zinc is not stored in the body, toxicity from long-term use of large zinc supplements can have the following significant effects: (Hooper PL, 1980)
Low copper status Altered iron function Reduced immune function Reduced levels of high-density lipoproteins (Hooper PL, 1980)