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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 disorders.

Unsubstantiated claims

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

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

Zinc is also claimed to shorten the duration of the common cold. However, not all studies have 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

Breastfeeding women (1st 6 months)

19 mg

Breastfeeding 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, an inherited condition that affects the skin, hair, and intestinal tract, increase the need for zinc. Other reasons for increased need include 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 disorders that lead to a pancreatectomy (surgical 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 breastfeeding 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 diminished immune system function. Moderate zinc 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 from exposure to zinc in normal dietary sources. Foods cooked in galvanized (zinc-plated) cookware can cause gastrointestinal upsets. Amounts of 2 or more grams of zinc will produce zinc toxicity. Symptoms of toxicity include drowsiness, poor memory, impaired motor skills, 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 including bran products, protein, and phytates (found in plants and seeds) 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.

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