Definition Zinc is an essential trace mineral. It has many functions in the body. Also, it is a component of several enzymes.
What food source is the nutrient found in? The best sources of zinc include animal foods such as oysters, extra-lean meats, poultry, fish and organ meats. Dairy products and eggs supply zinc in smaller amounts.
Whole-grain products, wheat germ, black-eyed peas, beans, nuts, seeds, and fermented soybean paste (miso) also contain zinc. However, the form of the mineral that is found in these foods is less available to the body. The zinc in breast milk is better absorbed in infants than that found in infant formulas or cow's milk.
Specific sources of zinc include:
oysters (6 medium) = 49.8 milligrams (mg)
beef, ground lean (90 grams) = 4.6 mg
turkey, dark meat (90 grams) = 3.8 mg
raisin bran (1 cup) = 3.0 mg
milk, lowfat (1 cup) = 1 mg
almonds (30 grams) = 1 mg
How does the nutrient affect the body? Zinc is essential for many of the body's functions. It makes up part of more than 200 enzymes in the body. Enzymes are proteins that enable different chemical reactions to take place in the body. Zinc is crucial for proper growth. It promotes cell reproduction and tissue growth and repair. This is necessary for wound healing. Zinc is also essential for the proper functioning of the immune system.
Zinc has many other functions, as well. It helps in the detoxification of alcohol in the liver, assists in the production of proteins, aids in the proper use of insulin to help regulate blood sugar levels, and helps in normal taste perception. Zinc also helps the body turn carbohydrates, proteins and fats into energy.
Taking the recommended amounts of zinc may aid in the metabolism of vitamin D and calcium. This could help reduce bone loss, such as osteoporosis. Zinc also assists in the transportation of vitamin A in the blood.
Information The Recommended Daily Intake (RDI) for zinc is 15 mg for males, age 11 and over and 12 mg for females, age 11 and over. Pregnant women should get 15 mg. Women who are breastfeeding should get 19 mg the first six months and 16 mg the second six months. A well-balanced diet will provide about 10 to 15 mg per day. Stomach acid is important to the absorption of zinc. Health problems or medications that lower stomach acid could limit the amount of zinc that is absorbed.
Zinc deficiency could lead to:
slowed growth
reduced taste, smell, and vision perceptions
poor appetite
mental lethargy
low sperm count
birth defects
impaired nerve conduction
nerve damage
poor healing of wounds
skin changes
reduced resistance to infections
Several factors can lead to a zinc deficiency. One is a high-fibre diet that contains high amounts of phytates. These are found in unrefined cereal and unleavened whole grain products. Phytates bind to zinc and reduce its absorption. The leavening agents used in most breads usually deactivate the phytates.
Another factor is diet restriction. Vegetarians and especially vegans (people who do not eat meat, eggs, dairy products, and seafood) may have a more difficult time taking in enough zinc. Taking large amounts of iron or copper in the form of supplements or from fortified foods without taking zinc, can also produce a zinc deficiency. Groups at higher risk for zinc deficiency include pregnant women, the elderly and athletes.
Some studies have suggested that zinc may help cure the common cold or at least decrease the duration of a cold. Zinc lozenges are a big seller for this reason. More research needs to be conducted to prove this theory. Zinc is relatively non-toxic in doses up to 45 mg per day. Doses higher than 150 mg can cause diarrhoea, abdominal cramps, and vomiting. High doses can interfere with the body's immune function. Taking doses higher than the recommended level can also interfere with the absorption of copper, another key mineral. This can cause a copper deficiency. High doses can also reduce iron absorption. Megadoses of Zinc may also lower HDL ("good") cholesterol levels. Taking more than the recommended amount of zinc from a supplement has no proven benefits and can cause several risks.
Eating lean meat regularly will ensure the proper level of zinc intake. Vegetarians can meet the RDI for zinc by eating a variety of beans, cheese, milk, nuts, seeds, wheat germ, and soy products.
Author: Kimberly Tessmer, RD, LD Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 11/1/2005 Contributors Potential conflict of interest information for reviewers available on request
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