Zinc

Overview

Zinc is necessary for the functioning of over 300 different enzymes and, as such, it plays a vital role in an enormous number of biological processes. Zinc is widely distributed in microorganisms, plants, and animals. In humans, the highest concentrations of zinc are found in the liver, pancreas, kidneys, bone, and muscles. Zinc is highly concentrated in parts of the eye, prostate gland, sperm, skin, hair, and nails. Cooking acidic foods in galvanized cookware used to be a possible source of excess zinc intake. The widespread use of stainless steel and plastic materials to prepare and store foods has largely eliminated this problem. Galvanized pipes in older plumbing systems used to leach zinc into drinking water supplies, but modern plumbing has phased out the use of galvanized pipes.

Dosage Info

Dosage Range

2-50mg elemental zinc daily. Doses of zinc sulfate as high as 220mg, three times a day have been evaluated for the treatment of sickle cell disease. (1)

Most Common Dosage

25mg daily.

23% elemental zinc contained in zinc sulfate
14.3% elemental zinc contained in zinc gluconate

Dosage Forms

Tablets, capsules, liquid, and lozenges.

Adult RDI

15mg

Adult ODA

15-35mg

RDA

  • Infants < 6 months: 2mg (Adequate Intake, AI)
  • Infants 7-12 months: 3mg
  • Children 1-3 years: 3mg
  • Children 4-8 years: 5mg
  • Children 9-13 years: 8mg
  • Males 14-18 years: 11mg
  • Females 14-18 years: 9mg
  • Males >19 years: 11mg
  • Females >19 years: 8mg
  • Pregnancy 14-18 years: 13mg
  • Pregnancy >19 years: 11mg
  • Lactation 14-18 years: 14mg
  • Lactation >19 years: 12mg

Interactions and Depletions

Interactions

Depletions

Active Forms

Zinc arginate, ascorbate, aspartate, citrate, gluconate, glycinate, histidinate, methionate, oxide, picolinate, and sulfate.

Absorption

Zinc absorption takes place in the intestinal lumen. Zinc absorption depends on the secretion of a zinc-binding factor from the pancreas.

Toxicities & Precautions

General

Zinc is relatively non-toxic, and although toxicity has been reported in humans, it is uncommon. Ingestion of high levels of zinc can induce a copper deficiency. Doses of 45mg/day are safe, but regular intake greater than 150mg/day could be a problem.

Zinc toxicity can cause diarrhea, dizziness, drowsiness, vomiting, loss of muscle coordination, and lethargy.

Inhalation of zinc oxide in certain industrial environments can also be a source of excess exposure.

Side Effects

Zinc gluconate lozenges may cause a mild stomach upset and a metallic taste in the mouth while using them. (2) Larger doses of other zinc salts have been associated with GI symptoms.

Functions in the Body

Immune System

Helps regulate a wide variety of immune system activities, including T-lymphocytes, CD4, natural killer cells, and interleukin II.

Antioxidant

Cofactor for the antioxidant enzyme Zn/Cu superoxide dismutase.

Wound Healing

Facilitates wound healing, especially in burns, surgical, and other types of scars.

Anti-viral Activity

Although its mechanism is not known at this time, zinc apparently possesses antiviral activity.

Sexual Function

Zinc is necessary for the maturation of sperm, for ovulation, and for fertilization.

Sensory Perceptions

Involved in sensory perceptions of taste, smell and vision. Necessary for salt-taste perception, dark adaptation, and night vision.

Serum Vitamin A Levels:

Controls the release of stored vitamin A from the liver.

Insulin Activity

Is a component of insulin and recently was discovered to be a regulator of insulin activity.

Thyroid

Promotes the conversion of thyroxine to triiodothyronine.

Clinical Applications

Common Cold

Zinc gluconate lozenges (3) and zinc nasal gel (4) substantially reduce the symptoms (coughing, headache, hoarseness, congestion, nasal drainage, and sore throat) and the duration of the common cold.

Immune Function

Zinc deficiency causes a decrease in antibody-mediated responses to both T-cell dependent and T-cell independent antigens and reduced natural killer cell activity and delayed-type hypersensitivity (DTH) reactions. (5) , (6)

Acne

Numerous studies report low zinc levels in individuals with acne, and oral zinc supplementation helps a substantial number of these patients. (7) , (8)

Benign Prostatic Hypertrophy (BPH)

Zinc inhibits 5-alpha reductase activity, which reduces the conversion of testosterone to dihydrotestosterone and decreasing hyperplastic growth in the prostate gland. (9)

Crohn's Disease

Patients with inflammatory bowel disease improve rapidly with zinc supplementation ranging from 210-750mg of zinc sulfate daily. (10) , (11)

Macular Degeneration

Two zinc-dependant enzymes are required for vision; patients taking 80mg of zinc daily for two years had much less vision loss than controls. (12) , (13)

Osteoporosis

Zinc enhances vitamin D activity and is essential for bone formation. Women with higher zinc intake have greater forearm bone mineral content. (14) , (15) , (16)

Skin Conditions

Individuals with eczema (17) and psoriasis (18) are frequently found to have low zinc levels.

Wound Healing

When zinc levels are low, zinc supplementation speeds wound healing; (19) topical applications speeds the healing of open wounds. (20)

Ulcers

Zinc sulfate (220mg three times a day) decreased pain and reduced the size of gastric ulcers much faster than placebo controls. (21)

Arthritis

Zinc has anti-inflammatory properties, probably due to its antioxidant activity in the enzyme superoxide dismutase. In a double-blind study, patients taking 220mg of zinc sulfate 3 times daily gained improvement in joint swelling, morning stiffness, walking time, and the patient's own impression of overall disease activity. (22) , (23)

Diabetes

Individuals with IDDM (24) and NIDDM (25) have been found to be zinc deficient.

Symptoms and Causes of Deficiency

Marginal zinc deficiencies are reported to be common in the United States. Because of its extensive range of biological activities, zinc deficiency can cause a wide range of deficiency symptoms. The symptoms of zinc deficiency are: acne, impaired sense of smell and taste, delayed wound healing, anorexia, decreased immunity, frequent infections, depression, photophobia, night blindness, problems with skin, hair and nails, menstrual problems, joint pain, and involuntary, cyclical movements of the eyeball (nystagmus).

    Zinc deficiency conditions were first reported in the 1950s in growing children and adolescent males from Iran, Iraq, and Turkey. Diets low in animal protein and high in phytate-containing grains produced symptoms of dwarfism, hypogonadism and failure to mature sexually. Pregnant women have greater zinc needs. Deficiency can cause impaired fetal development, low birth weight infants, and birth defects. Stretch marks during pregnancy are also partially due to zinc deficiency. Zinc deficiency can be caused by inadequate dietary intake due to foods grown on zinc depleted soils. Food processing also removes zinc, so fast foods and processed foods are also zinc depleted. Protein and/or calorie-restricted diets can lead to zinc deficiency. Zinc depletion is frequently seen in the following medical conditions: alcoholism, macular degeneration, diabetes, malignant melanoma, liver and kidney diseases, malabsorption syndromes such as celiac sprue, and inflammatory bowel diseases such as Crohn’s disease. ·

Dietary Sources

The best dietary sources of zinc are lean meats, liver, eggs, and seafood (especially oysters). Whole grain breads and cereals are also good sources of zinc.

References

  1. View Abstract: Gupta VL, Chaubey BS. Efficacy of zinc therapy in prevention of crisis in sickle cell anemia: a double blind, randomized controlled clinical trial. J Assoc Physicians India. Jul 1995;43(7):467-469.
  2. View Abstract: Macknin ML, Piedmonte M, Calendine C, Janosky J, Wald E. Zinc gluconate lozenges for treating the common cold in children: a randomized controlled trial. JAMA. Jun1998;279(24):1962-1967.
  3. View Abstract: Mossad SB, et al. Zinc Gluconate Lozenges for Treating the Common Cold. A Randomized, Double-blind, Placebo-controlled Study. Ann Intern Med. Jul1996;125(2):81-88.
  4. View Abstract: Mossad SB. Effect of zincum gluconicum nasal gel on the duration and symptom severity of the common cold in otherwise healthy adults. QJM. Jan2003;96(1):35-43.
  5. View Abstract: Fraker PJ, et al. Interrelationships Between Zinc and Immune Function. Fed Proc. Apr1986;45(5):1474-79.
  6. View Abstract: Taylor CG, et al. Dietary zinc deficiency and expression of T lymphocyte signal transduction proteins. Can J Physiol Pharmacol. Oct2000;78(10):823-8.
  7. View Abstract: Michaelsson G, et al. Patients with Dermatitis Herpetiformis, Acne, Psoriasis and Darier's Disease have Low Epidermal Zinc Concentrations. Acta Derm Venereol. 1990;70(4):304-8.
  8. View Abstract: Leake A, et al. The Effect of Zinc on the 5 Alpha-reduction of Testosterone by the Hyperplastic Human Prostate Gland. J Steroid Biochem. Feb1984;20(2):651-55.
  9. Hendricks KM, Walker WA. Zinc Deficiency in Inflammatory Bowel Disease. Nutr Rev. 1988;46(12):401-08.
  10. View Abstract: Sturniolo GC, et al. Zinc supplementation tightens "leaky gut" in Crohn's disease. Inflamm Bowel Dis. May2001;7(2):94-8.
  11. View Abstract: Newsome DA, et al. Oral Zinc in Macular Degeneration. Arch Ophthalmol. Feb1988;106(2):192-98.
  12. View Abstract: Christian P, et al. Zinc supplementation might potentiate the effect of vitamin A in restoring night vision in pregnant Nepalese women. Am J Clin Nutr. Jun2001;73(6):1045-51.
  13. View Abstract: Angus RM, et al. Dietary Intake and Bone Mineral Density. Bone Miner. Jul1988;4(3):265-77.
  14. View Abstract: Igarashi A, et al. Increase in bone protein components with healing rat fractures: enhancement by zinc treatment. Int J Mol Med. Dec1999;4(6):615-20.
  15. View Abstract: Saltman PD, et al. The role of trace minerals in osteoporosis. J Am Coll Nutr. Aug1993;12(4):384-9.
  16. View Abstract: David TJ, et al. Low Serum Zinc in Children with Atopic Eczema. Br J Dermatol. Nov1984;111(5):597-601.
  17. View Abstract: Michaelsson G, et al. Patients with Dermatitis Herpetiformis, Acne, Psoriasis and Darier's Disease have Low Epidermal Zinc Concentrations. Acta Derm Venereol. 1990;70(4):304-08.
  18. View Abstract: Okada A, et al. Zinc in Clinical Surgery--A Research Review. Jpn J Surg. Nov1990;20(6):635-44.
  19. View Abstract: Agren MS, et al. Release and Absorption of Zinc from Zinc Oxide and Zinc Sulfate in Open Wounds. Acta Derm Venereol. 1991;71(4):330-33.
  20. View Abstract: Frommer DJ. The Healing of Gastric Ulcers by Zinc Sulphate. Med J Aust. Nov1975;2(21):793-96.
  21. View Abstract: Simkin PA. Oral Zinc Sulphate in Rheumatoid Arthritis. Lancet. Sep1976;2(7985):539-42.
  22. View Abstract: Peretz A, et al. Effects of zinc supplementation on the phagocytic functions of polymorphonuclears in patients with inflammatory rheumatic diseases. J Trace Elem Electrolytes Health Dis. Dec1994;8(3-4):189-94.
  23. View Abstract: Nakamura T, et al. Kinetics of Zinc Status in Children with IDDM. Diabetes Care. Jul1991;14(7):553-57.
  24. Pidduck HG, et al. Plasma Zinc and Copper in Diabetes Mellitus. Diabetes. Apr1970;19(4):234-39.