Zinc is a trace mineral you need for good health. In his book, "Staying Healthy with Nutrition," Dr. Elson Haas states that zinc's importance in human nutrition was not recognized until 1934, and it wasn't until the 1960s that zinc deficiency was linked to specific health problems. Due to long-standing industrial agricultural practices, zinc is becoming less available in soils and less abundant in plant foods. However, some foods still contain reasonable amounts of zinc, and oysters are a particularly rich source.
Functions
Since zinc's role in preventing arrested growth in adolescents was first described in 1961, scientists have learned that zinc is required for dozens of biological reactions in your cells and is probably involved in more metabolic functions than any other mineral. According to the Linus Pauling Institute, zinc acts as an essential cofactor for many enzymes and lends structural support to a variety of proteins. Zinc protects your cell membranes from oxidative injury, assists in the production and secretion of several hormones, participates in chromosomal function and serves a role in cell signaling, which involves the use of chemical messengers to coordinate the activities of your tissues and organs.
Sources
Zinc is commonly added to animal feeds to increase growth, so beef, pork and lamb are relatively good sources. Liver is high in zinc, as are herring and some other fish. Whole grains, nuts, pumpkin seeds, ginger root, mustard seed, chili powder and black pepper contain significant amounts, but the zinc from plant sources is not as readily absorbed as that from animal sources. Oysters are a particularly rich zinc source, containing 10 times as much as other foods by weight. However, oysters also contain high amounts of copper, and they can be contaminated with pollutants and infectious organisms.
Deficiency
Haas believes zinc deficiency is more common than many health care experts realize. Around 75 percent of Americans consume less than 15 mg of zinc daily, and half get less than 8 mg. Most people don't regularly eat zinc-rich foods, such as oysters. Signs and symptoms of zinc deficiency include poor growth and development in children, poor sperm development in men, increased susceptibility to infection, skin rashes, hair loss, persistent diarrhea, poor wound healing, night blindness, corneal opacity, abnormal taste sensation and behavioral disturbances. "The Merck Manual of Diagnosis and Therapy" reports that maternal zinc deficiency can cause fetal malformations and low birth weight.
Considerations
Mild zinc deficiency may be a common but unrecognized problem. A serving of six medium oysters contains approximately 77 mg of zinc, but oysters are not on many people's menus, and shellfish must be consumed with care due to risks of contamination. Recommended dietary allowances for zinc -- the doses required to prevent deficiency -- vary from 2 mg daily for infants to 13 mg for nursing teenage mothers. Higher doses might be needed for optimal health. Ask your doctor if you could benefit from taking a zinc supplement.
References
- "Staying Healthy with Nutrition"; Elson M. Haas, M.D.; 2006
- Linus Pauling Institute; Zinc; Jane Higdon; December 2003
- "The Merck Manual of Diagnosis and Therapy, 18th Edition: Zinc"; Mark H. Beers, M.D., ed.; 2006
- Office of Dietary Supplements: Zinc
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