Zinc

Other Name(s):

zinc gluconate, zinc sulfate

General Description:

Zinc is an essential trace element. It is almost as plentiful in the human body as iron, and is concentrated in the eyes, brain, pancreas, kidneys, liver and adrenal gland. In 1956, it was recognized as an essential nutrient.

Zinc is necessary for insulin to work effectively, and is involved in protein and DNA synthesis. Bone and teeth need zinc for proper mineralization. Zinc is necessary to prevent birth defects.

Zinc functions in the exchange of carbon dioxide between the lungs and the blood stream, and appears in enzymatic functions in the liver and intestine.

Medically Valid Uses:

Zinc is not widely used to treat any medical condition except deficiencies that are associated with malnutrition and/or malabsorption, as in the case of TPN solutions (intravenous feeding).

Unsubstantiated Claims:

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Zinc is claimed to help wound healing, maintain normal levels of vitamin A and improve the immune system. It is also claimed to maintain normal oil-gland function, improve sex drive and slow the aging process.

In one study, zinc gluconate appeared to significantly shorten the duration of the common cold. Sixty-five patients dissolved one 23 mg zinc tablet (one-half tablet for children) in their mouth every 2 hours until all symptoms were absent for 6 hours; 11 percent were asymptomatic within 12 hours, 22 percent within 24 hours. Other studies have not repeated this finding.

Recommended Intake:

As indicated below, zinc is measured in milligrams (mg). The RDA is the Recommended Dietary Allowance.

Group

RDA

Infants (0 to 1 year)

5 mg

Children (1 to 10 years)

10 mg

Boys (11+ years)

15 mg

Girls (11+ years)

12 mg

Pregnant women

15 mg

Breast-feeding women (1st 6 months)

19 mg

Breast-feeding women (2nd 6 months)

16 mg

Zinc preparations are available in a wide range of doses. Zinc supplements come in two primary forms: zinc sulfate and zinc gluconate. Zinc sulfate contains higher concentrations of zinc (23 percent per 100 mg) than zinc gluconate (14.3 percent per 100 mg). When buying supplements, read the packaging carefully to ensure you are buying what you want to take. Take zinc with food to avoid stomach problems.

Food source

Nutrient content per 100 grams

Oyster

161 mg

Herring

111 mg

Turkey meat

13.8 mg

Wheat germ

13.8 mg

Yeast

9.9 mg

Molasses

7.9 mg

Soybeans

6.9 mg

Chicken meat

4.8 mg

Whole wheat bread

2.7 mg

Eggs

1.3 mg

Down syndrome, some anemias (including sickle cell and thalassemia) and acrodermatitis enteropathica increase the need for zinc. Other reasons for increased need are extensive burns, diabetes, prolonged stress or trauma and chronic use of diuretics.

Malabsorption syndromes may also cause increased need for zinc. These syndromes may include Crohn's disease, tropical and non-tropical sprue, celiac disease, cystic fibrosis, ulcerative colitis and a pancreatectomy (removal of all or part of the pancreas). Intestinal parasites can also increase the need for zinc supplements.

Alcoholism, cirrhosis of the liver and eating disorders (such as anorexia and bulimia) can also increase the need for zinc.

Women who are pregnant or breast-feeding may need to take mineral supplements, but must consult a physician before doing so.

Acrodermatitis enteropathica, a disease of infants characterized by hair loss, diarrhea and dermatitis, is a rare inherited disorder associated with abnormal zinc metabolism. This condition is treated by providing zinc supplements.

Zinc deficiency in adults can lead to iron-deficiency anemia and pigmentary changes in the skin. It may also lead to loss of sense of smell, changes in taste perception, anorexia, hair loss and a decreased immune function. Moderate deficiencies may lead to decreased testicular function in men.

Other symptoms include liver enlargement, impaired mental function, rashes, skin lesions, mouth sores, inflammation of the eyelids, infection of the skin around the fingernails and impaired healing.

Side Effects, Toxicity and Interactions:

Toxicity has not been observed in normal dietary sources. Foods cooked in galvanized (zinc-plated) cooking utensils can cause gastrointestinal upsets. Amounts of 2 or more grams of zinc will produce zinc toxicity. Symptoms of toxicity are gastrointestinal disturbances, muscle incoordination, drowsiness, nausea, vomiting and diarrhea.

People with a copper deficiency should use zinc with caution because it can induce or worsen copper deficiency.

A chronic intake of large amounts of zinc can result in a copper deficiency because it competes with copper absorption. Some foods that include bran products, protein and phytates may decrease zinc absorption

Red wine and lactose in milk aid in zinc absorption.

Additional Information:

Infants absorb zinc from breast milk extremely well. Breast milk has a zinc-binding enzyme that enhances the ability of infants to absorb zinc through the intestine.

Supplements may cause an unpleasant metallic taste in the mouth.

Click here for a list of reputable Web sites with general information on nutrition.

References:

  1. Behrman RE, Kliegman RM, Nelson EE, Vaughan VC, eds. Nelson Textbook of Pediatrics. 14th ed. Philadelphia, PA: W.B. Saunders Co.; 1992.

  2. Braunwald E, Isselbacher KJ, Petersdorf RG, Wilson JD, Martin JB, Fauci AS, eds. Harrison's Principals of Internal Medicine. 11th ed. New York, NY: McGraw-Hill; 1987.

  3. Smolin LA, Grosvenor MB. Nutrition Science and Applications. 2nd ed. Sanders College Publishing; 1997.

  4. Leonard MB, Zemel BS, Kawchak DA, et al. Plasma zinc status, growth, and maturation in children with sickle cell disease. Journal of Pediatrics. 1998;132(3):467-471.

  5. USP DI 19th ed. Englewood, CO: Micromedex Inc.; 1999

  6. Zinc Supplements. Facts and Comparisons. St Louis, MO: Facts & Comparisons; 1991.

  7. Cousins RJ. Zinc. In: Filer LJ, Ziegler EE, eds. Present Knowledge in Nutrition. 7th ed. Washington, DC: International Life Sciences Institute Press; 1996:293-306.

  8. King JC, Keen CL. Zinc. In: Shils ME, Olson JA, Shike M, eds. Modern Nutrition in Health and Disease. 8th ed. Philadelphia, PA: Lea & Febiger; 1994:214-230.

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