Zinc is an essential trace mineral, which, next to iron, is the second most
abundant trace mineral in the body. It is a component in over 200 enzymes. Zinc
is stored primarily in muscle but high concentrations are also found in red and
white blood cells and the retina. It is also found in bones, skin, kidney,
liver, and pancreas. In men, the prostate gland contains more zinc than any
Zinc is a part of some important antioxidant compounds, including superoxide
dismutase (SOD) and zinc monomethionine. It protects the liver from chemical
damage, helping with detoxification of the body. It is required for a healthy
immune system. Taking zinc supplements has been shown to reduce infection and
speed wound healing. Studies have shown it helps treat and prevent acne. It is
essential for proper growth and development, especially early in life. It is
necessary to maintain proper vision, taste, and smell.
Zinc deficiency may be a more common problem than previously thought,
especially as people age. In clinical studies on the effects of zinc
supplementation in the elderly, zinc improved immune system function, reduced
the incidence of illness, and decreased the incidence of anorexia.
Recent research has been conducted to determine the true value of zinc
lozenges in preventing or reducing cold symptoms.
Zinc absorption from foods varies from 20% to 40% of ingested zinc. Zinc from
animal foods is the best absorbed form. When bound with the phytates or oxalates
in vegetable sources, zinc is less available, and vegetable fiber itself impedes
the absorption of zinc. Dairy products and eggs contain fair amounts of zinc,
but again, it may be poorly absorbed from these sources.
The following foods contain high amounts of zinc in the most absorbable
- Oysters (richest source)
- Red meats
- Shrimp, crab, and other shellfish
Other good sources, but which may be less absorbable, include legumes
(especially lima beans, black-eyed peas, pinto beans, soybeans, peanuts) whole
grains, miso, tofu, brewer's yeast, cooked greens, mushrooms, green beans, and
Zinc is a metallic element present in soil.
The most commonly used zinc supplement has been zinc sulfate. This is the
least expensive form, but it may cause gastric irritation and is less absorbable
than other forms. It is usually prescribed as 220 mg zinc sulfate, which
provides approximately 55 mg of elemental zinc. More absorbable forms such as
the following are available.
- Zinc picolinate
- Zinc citrate
- Zinc acetate
- Zinc glycerate
- Zinc monomethionine
These forms come in capsules supplying 30 or 50 mg of elemental zinc. The
amount in milligrams per capsule of these other zinc compounds can vary,
according to the percentage of elemental zinc contained. Zinc lozenges are also
available, which supply varying amounts of zinc and are used for treating
Benefits of zinc include the following.
- Treats depressed immunity
- Improves wound healing
- Treats and may prevent acne
- May prevent macular degeneration
- Treats anorexia nervosa (anorexia is a symptom of zinc deficiency,
and the teenage population is at higher risk for zinc deficiency due to dietary
- Improves male fertility and sexual function, especially among
- Treats rheumatoid arthritis
- Treats Wilson's disease (a disorder of excess copper
- Decreases taste alteration during cancer treatments
- Improves sense of taste and smell
Some conditions may impair zinc absorption, or increase the need for zinc.
Individuals with the following conditions may benefit from zinc
- Acrodermatitis enteropathica (the inherited disease of zinc
- Pregnancy, lactation
- Kidney disease, dialysis
- Celiac disease
- Inflammatory bowel disease, ulcerative colitis
- Chronic diarrhea
- Pancreatic insufficiency
- Oral contraceptive use
- Prostate problems (BPH, prostatitis,
|Dosage Ranges and Duration of
The RDA for zinc is as follows.
- Infants to 1 year: 5 mg
- 1 to 10 years: 10 mg
- Males over 10 years: 15 mg
- Females over 10 years: 12 mg
- Pregnant females: 15 mg
- Lactating females: (0 to 6 months) 19 mg, (6 to 12 months) 16
Therapeutic ranges (elemental zinc):
- Men: 30 to 60 mg daily
- Women: 30 to 45 mg daily
Doses over this amount should be limited to only a few months under the
supervision of a health care professional.
Zinc is the least toxic trace mineral. Symptoms of toxicity are GI irritation
and vomiting, usually occurring after a dose of 2,000 mg or more has been
ingested. Studies have confirmed that up to 10 times the RDA (150 mg) taken even
over time was not toxic. Doses this high are unnecessary and interfere with the
assimilation of other trace minerals such as copper and iron.
Too much zinc (over 150 mg/day over time) lowers HDL cholesterol and raises
LDL cholesterol, an undesirable effect. Megadoses of zinc are reported to
depress immune function. Studies on this have been inconclusive, and further
research is needed.
Zinc sulfate can cause gastric irritation, but another form can be used
instead if this occurs. Other reported side effects of zinc toxicity are
dizziness, headache, drowsiness, increased sweating, muscular incoordination,
alcohol intolerance, hallucinations, and anemia.
Because of the multiple interactions zinc has with other nutrients, it is
advisable to take a balanced multiple vitamin/mineral preparation that contains
zinc as well as copper, iron, and folate, to help prevent deficiencies of these
Postmenopausal women treated with conjugated estrogens and
medroxyprogesterone acetate experienced reductions in zinc excretion of 35%
after 3 months and 26% after one year (Herzberg et al. 1996). The reduction was
more pronounced in women with osteoporosis who had elevated zinc excretion at
the beginning of the study. The clinical significance of this interaction is
There is a case report of a 58-year-old woman who developed a lupus
erythematosus-like syndrome within 1 week following the addition of zinc
sulphate therapy (200 mg po tid) to her drug regimen (30 to 200 mg/day
hydralazine; 120 to 640 mg/day propranolol; polythiazide; potassium chloride;
propylthiouracil; and thyroxine) for the treatment of leg ulcers (Fjellner
1979). Her symptoms included fever, abdominal distress, facial butterfly rash,
enlargement of the leg ulcers, oral ulcers, and maculopapular eruptions on legs,
trunk, and arms. Withdrawal of zinc prompted clinical improvement, including
healing of the oral ulcers and remission of the fever and abdominal distress.
However, the patient's condition did not resolve completely until all the
medications except thyroxine also were discontinued.
Anti-inflammatory Drugs (NSAIDs)
Zinc interacts with anti-inflammatory medications by forming complexes with
these drugs (Dendrinou-Samara et al. 1998).
Quinolone antibiotics form chelates with metal cations, such as aluminum,
magnesium, calcium, iron, zinc, copper, and manganese (Kara et al. 1991; Li et
al. 1999), which significantly reduces the absorption of these medications
(Balfour and Wiseman 1999; Brouwers 1992; Campbell and Hasinoff 1991). Dietary
supplements and antacids containing aluminum and magnesium should be taken two
to four hours before or after administration of these antibiotics (Hines Burnham
et al. 2000; Li et al.
Tetracyclines form chelates with divalent and trivalent cations, including
iron, aluminum, magnesium, and calcium (Neuvonen 1976). These chelates are
poorly soluble and can significantly reduce the absorption and efficacy of
tetracyclines (Hines Burnham et al. 2000; Neuvonen 1976). However, in an in
vitro study, zinc-drug interactions in gastrointestinal fluid influenced the
bioavailability of both zinc and tetracycline or tetracycline analogs (Brion et
Balfour JA, Wiseman LR. Moxifloxacin. Drugs. 1999;57(3):363-374.
Brion M, Lambs L, Berthon G. Metal ion-tetracycline interactions in
biological fluids. Part 5. Formation of zinc complexes with tetracycline and
some of its derivatives and assessment of their biological significance.
Agents Actions. 1985;17:230-242.
Brouwers JR. Drug interactions with quinolone antibacterials. Drug
Campbell NR, Hasinoff BB. Iron supplements: a common cause of drug
interactions. Br J Clin Pharmacol. 1991;31(3):251-255.
Dendrinou-Samara C, Tsotsou G, Ekateriniadou E, et al. Anti-inflammatory
drugs interacting with Zn(II), Cd(II) and Pt(II) metal ions. J Inorg Biochem.
1998; 71: 171-179.
Eby GA. Zinc ion availability—the determinant of
efficacy in zinc lozenge treatment of common colds. J Antimicrob
Feltman J. Prevention's Food & Nutrition. Emmaus, Pa: Rodale
Fjellner B. Drug-induced lupus erythematosus aggravated by oral zinc therapy.
Acta Dermatovener. 1979;59:368-370.
Fortes C, Forastiere F, Agabiti N, et al. The effect of zinc and vitamin A
supplementation on immune response in an older population. J Am Geriatr
Garland ML, Hagmeyer KO. The role of zinc lozenges in treatment of the common
cold. Ann Pharmacother. 1998;32:63-69.
Golik A, Zaidenstein R, Dishi V, et al. Effects of captopril and enalapril on
zinc metabolism in hypertensive patients. J Am Coll Nutr.
Haas E. Staying Healthy with Nutrition: The Complete Guide to Diet and
Nutritional Medicine. Berkeley, Calif: Celestial Arts Publishing; 1992.
Hendler SS. The Doctors' Vitamin and Mineral Encyclopedia. New York,
NY: Fireside Press; 1991.
Herzberg M, Lusky A, Blonder J, Frenkel Y. The effect of estrogen replacement
therapy on zinc in serum and urine. Obstet Gynecol.
Hines Burnham, et al, eds. Drug Facts and Comparisons. St. Louis,
MO:Facts and Comparisons; 2000:1295.
Kara M, Hasinoff BB, McKay DW, et al. Clinical and chemical interactions
between iron preparations and ciprofloxacin. Br J Clin Pharmacol.
Leake A, Chisholm GD, Habib FK. The effect of zinc on the
5a-reduction of testosterone by the hyperplastic
prostate gland. J Ster Biochem. 1984;20:651-655.
Li RC, Lo KN, Lam JS, et al. Effects of order of magnesium exposure on the
postantibiotic effect and bactericidal activity of ciprofloxacin. J
Lieberman S, Bruning N. The Real Vitamin & Mineral Book. 2nd ed.
New York, NY: Avery Publishing Group; 1997.
Murray M. Encyclopedia of Nutritional Supplements. Rocklin, Calif:
Prima Publishing; 1996.
Neuvonen PJ. Interactions with the absorption of tetracyclines. Drugs.
Pronsky Z. Food-Medication Interactions. 9th ed. Pottstown, Pa:
Food-Medicine Interactions; 1995.
Sazawal S, Black RE, Jalla S, et al. Zinc supplementation reduces the
incidence of acute lower respiratory infections in infants and preschool
children: a double-blind, controlled trial. Pediatrics. 1998;102(part
Shealy CN. The Illustrated Encyclopedia of Healing Remedies. Boston,
Mass: Element Books Inc.; 1998.
Somer E. The Essential Guide to Vitamins and Minerals. New York, NY:
HarperCollins Publishers, Inc.; 1995.
Whitney E, Cataldo C, Rolfes S. Understanding Normal and Clinical
Nutrition. St. Paul, Minn: West Publishing Co.;
Copyright © 2000 Integrative Medicine
CommunicationsThis publication contains
information relating to general principles
of medical care that should not in any event be construed as specific
instructions for individual patients. The publisher does not accept any
responsibility for the accuracy of the information or the consequences arising
from the application, use, or misuse of any of the information contained herein,
including any injury and/or damage to any person or property as a matter of
product liability, negligence, or otherwise. No warranty, expressed or implied,
is made in regard to the contents of this material. No claims or endorsements
are made for any drugs or compounds currently marketed or in investigative use.
The reader is advised to check product information (including package inserts)
for changes and new information regarding dosage, precautions, warnings,
interactions, and contraindications before administering any drug, herb, or
supplement discussed herein.