Clinician Fact Sheet: Zinc
August 2001; Volume 4; S1-S2
In the United States, it is estimated that adults and children get two to six colds each year, at a cost of more than $3.5 billion. A number of studies have evaluated the use of zinc lozenges to reduce the duration of symptoms associated with the common cold; results have been conflicting.
In one representative, positive study, time to complete resolution of symptoms was significantly shorter in the zinc group compared to the placebo group (median, 4.4 days compared to 7.6 days, respectively).1 Patients taking one zinc lozenge (13.3 mg zinc from zinc gluconate) every two hours while awake experienced fewer days with coughing, headache, hoarseness, nasal congestion, nasal drainage, and sore throat. However, there was no difference in time to resolution of fever, muscle ache, scratchy throat, or sneezing, and the zinc group had significantly more side effects (nausea and bad aftertaste).
In recent studies, researchers have pointed to differences in product formulation to explain the variations in zinc studies.2,3 Citric acid, tartaric acid, sorbitol, and mannitol may reduce efficacy by binding the free zinc ion in the mouth. Patients opting to try zinc lozenges, should select a zinc gluconate product that does not contain these additives.
Recommended Dietary Allowances (RDA)
• 5 mg/d for children 0-1 y 15 mg/d for males 11 y and older
• 10 mg/d for children 1-10 y 12 mg/d for females 11 y and older
Food Sources
Dietary sources of zinc include oysters, meat, dairy products, nuts, raisins, legumes, and whole grains.
Formulation
The amount of elemental zinc differs depending upon the zinc formulation: Zinc sulfate contains 23% elemental zinc (220 mg zinc sulfate contains 50 mg zinc). Zinc gluconate contains 14.3% elemental zinc (10 mg zinc gluconate contains 1.43 mg zinc).
Mechanism of Action
• Zinc is an essential trace element and a cofactor in many biological processes, including DNA, RNA, and protein synthesis.
• Zinc plays a role in the body’s immune function, wound healing, reproduction, growth and development, behavior and learning, taste and smell, blood clotting, thyroid hormone function, and insulin action.
Clinical Uses
• To treat zinc deficiency associated with zinc-deficient diets, alcoholism, digestive diseases that result in chronic diarrhea, and restricticted diets, including anorexia nervosa.
• To treat the common cold and improve immune function.
• To treat blunted sense of taste (hypogeusia) and recurrent apthous ulcers.
• To treat Wilson’s disease.
• To ensure normal development and growth in children.
• To treat and prevent peptic ulcers.
• To treat acrodermatitis enteropathica.
• As adjunctive treatment in many chronic diseases, including sickle cell disease, Hansen’s disease, macular degeneration, and diabetes.
• To treat muscle cramps in zinc-deficient cirrhosis patients.
• Topically, to treat acne, herpes simplex infections, resistant trichomonas infections, and leg ulcers; to speed wound healing; to improve outcomes in burn patients; in toothpastes and mouthwashes to prevent dental plaque formation and gingivitis; and in ophthalmic products to soothe eye irritation.
• Intravenously, zinc is used as a component of total parenteral nutrition.
• When used parenterally, immediately post-head trauma, zinc improves the rate of neurological recovery.
Adverse Effects/Toxicity
• Zinc taken orally can cause nausea and vomiting, watery diarrhea, irritation and corrosion of the gastrointestinal tract, acute renal tubular necrosis, and interstitial nephritis.
• Toxicity presents with flu-like and central nervous systems symptoms including fever, coughing, nausea, vomiting, diarrhea, epigastric pain, lethargy, fatigue, neuropathy, and dehydration.
• Zinc gluconate lozenges can leave a bad aftertaste and may cause nausea.
• Zinc-induced copper deficiency has been associated with sideroblastic anemia, neutropenia, and impaired immune function at doses of 400 mg/d and greater.
• Zinc supplementation might reduce HDL levels and test results and increase the LDL to HDL ratio.
• Zinc supplementation can increase HgbA1C in type 1 diabetics.
Interactions/Nutrient Depletion
• Concomitant use with captopril, chlorthalidone, deferoxamine, and loop and thiazide diuretics can increase urinary zinc elimination.
• Concomitant use with amiloride and potassium-sparing diuretics can decrease urinary zinc elimination.
• Chlorthalidone can increase serum zinc levels.
• Concomitant use with interferon alfa-2b might be effective for treating necrolytic acral erythema associated with hepatitis C.
• With the exception of doxycycline, concomitant use with all tetracylines decreases zinc and tetracyline absorption.
• Concomitant use with cisplatin might increase the cytotoxicity of cisplatin when in the presence of chelate ethylenediaminetetraacetic acid, as compared to cisplatin treatment alone.
• Concomitant use with fluoroquinolones reduces zinc absorption and serum levels of fluoroquinolones.
• Penicillamine can reduce serum levels of zinc; concomitant use with penicillamine can reduce the effects of zinc from food or supplements.
• Concomitant administration with foods containing bran, protein, phytates, calcium, or phosphorus may decrease supplemental zinc absorption through a nonspecific binding function.
• Concomitant caffeine use can decrease zinc absorption.
• Concomitant zinc use can decrease copper absorption and increase zinc excretion.
• Iron taken in solution can inhibit the absorption of zinc, but foods fortified with iron do not.
• Use with caution in people who are homozygous for hemochromatosis.
• Avoid or use with caution with zinc ophthalmic solutions in glaucoma patients.
• Zinc absorption is reduced in people with rheumatoid arthritis.
• When testing blood for zinc and other trace elements, avoid powdered gloves to reduce the potential of sample contamination.
References
1. Mossad SB, et al. Zinc gluconate lozenges for treating the common cold. A randomized, double-blind, placebo-controlled study. Ann Intern Med 1996;125:81-88.
2. Garland ML, Hagmeyer KO. The role of zinc lozenges in treatment of the common cold. Ann Pharmacother 1998;32:63-69.
3. Marshall S. Zinc gluconate and the common cold. Review of randomized controlled trials. Can Fam Physician 1998;44:1037-1042.
Resources
Pelton R, et al. Drug-Induced Nutrient Depletion Hand-book. Hudson, OH: Lexi-Comp; 1999.
Zinc. Facts about Dietary Supplements. Office of Dietary Supplements. National Institutes of Health. Available at: www.cc.nih.gov/ccc/supplements/zinc.pdf. Accessed: May 21, 2001.
Natural Medicines Comprehensive Database [database online]. Stockton, CA: Therapeutic Research Center, Inc., 2000.
August 2001; Volume 4; S1-S2
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content