Zinc In The Diet
Zinc is a trace mineral needed for a healthy body. It forms part of many enzymes - proteins that govern the body's chemical reactions - and has many other functions.
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 cannot be used as well by 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 (3 ounces) = 4.6 mg
- turkey, dark meat (3 ounces) = 3.8 mg
- raisin bran (1 cup) = 3.0 mg
- milk, lowfat (1 cup) = 1 mg
- almonds (1 ounce) = 1 mg
How does the nutrient affect the body?
Zinc is required for many of the body's functions. It makes up part of more than 200 enzymes in the body. Enzymes are proteins that enable certain 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 needed for wound healing. Zinc is also key to the proper working of the immune system.
Zinc has many other functions, as well. It helps to:
- detoxify alcohol
in the liver
- assists in the making of proteins
- aids in the proper use of insulin to help control blood glucose levels
- helps in normal taste perception
Zinc also helps the body turn carbohydrates, proteins, and fats
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 moving vitamin A
through the blood.
The Recommended Daily Allowance (RDA) for zinc is 11 mg for males, age 14 and over and 8 mg for females, age 19 and over. Pregnant women should get 11 mg. Women who are breastfeeding should get 12 mg 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 medicines that lower stomach acid could limit the amount of zinc that the body absorbs.
Zinc deficiency can lead to:
- slowed growth
- reduced taste, smell, and vision
- 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-fiber diet that contains a lot 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 not getting enough zinc in the diet. Vegetarians, especially vegans who do not eat meat, eggs, dairy products, and seafood, may have a harder 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 result in a zinc deficiency. Groups at higher risk for this are pregnant women, the elderly, and athletes.
Some studies suggest that zinc may help cure the common cold or at least decrease the length of a cold. Zinc lozenges are a big seller for this reason. More research needs to be done to prove this theory. Zinc is not too toxic in doses up to 45 mg per day. Doses higher than 150 mg can cause diarrhea, abdominal cramps, and vomiting. High doses can also interfere with the body's immune function.
Taking doses higher than the recommended level can also prevent copper, another key mineral, from being absorbed well by the body. 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. As noted, it can cause several risks. Eating lean meat on a regular basis will ensure the proper level of zinc intake. Vegetarians can meet the RDA for zinc by eating a variety of beans, cheese, milk, nuts, seeds, wheat germ, and soy products.
Somer, E., MA, RD.&Health Media of America. (1995). The Essential Guide To Vitamins and Minerals (2nd ed.). New York: HarperCollins Publishers, Inc.
Duyff, R., MS, RD, CFCS. (1996). The American Dietetic Association's Complete Food&Nutrition Guide. Minnesota: Chronimed Publishing.
Mahan, K, MS, RD, CDE&Escott-Stump, S., MA, RD, LDN. (2000). Krause's Food, Nutrition,&Diet Therapy (10th ed.). Pennsylvania: W.B. Saunders Company.
Consumers Union of U.S., Inc. (November, 1997). "Do You Need More Minerals? Consumer Reports on Health, pp. 121-124.
USDA Nutrient Database for Standard Reference, Release 11, (Sept. 1996).
American Heart Association Web Site (January, 2000). Vegetarian Diets.
US Food and Drug Administration, Center for Food Safety and Applie Nutrition, (March, 1999). Economic Characterization of the Dietary Supplement Industry Final Report, Section 4.1.2.
Mayo Clinic Health Letter, (June, 1997). Vitamin and mineral supplements in the headlines.
WebMD Web Site (1999). Zinc in diet, Zinc Supplements