Zinc is an essential mineral that is a component of more than 300 enzymes needed to repair wounds, maintain fertility in adults and growth in children, synthesize protein, help cells reproduce, preserve vision, boost immunity, and protect against free radicals, among other functions.
Where is it found?
Good sources of zinc include oysters, meat, eggs, seafood, black-eyed peas, tofu, and wheat germ.
Zinc has been used in connection with the following conditions (refer to the individual health concern for complete information):
| Science Ratings | Health Concerns |
|---|---|
 |
Childhood intelligence (for deficiency) Common cold/sore throat (as lozenges) Infertility (male) (for deficiency) Night blindness (for deficiency) Wound healing (oral and topical) |
 |
Anemia (for thalassemia if deficient) Attention deficit–hyperactivity disorder (ADHD) Burns (zinc, copper, and selenium, intravenously, for extensive burns) Canker sores (for deficiency only) Celiac disease (for deficiency) Cold sores (topical) Common cold (as nasal spray) Common cold/sore throat (orally) Gingivitis (zinc plus bloodroot toothpaste) Halitosis (zinc chloride rinse or toothpaste) Hepatitis C (zinc-L-carnosine) Immune function (for elderly people) Liver cirrhosis (for deficiency) Skin ulcers (oral and topical zinc) Sprains and strains (if deficient) Tinnitus (for deficiency only) Type 2 diabetes (preferably for those with a documented deficiency) |
 |
Benign prostatic hyperplasia (BPH) Contact dermatitis Dermatitis herpetiformis (for deficiency) Immune function (for non-elderly people) Insulin resistance syndrome (Syndrome X) Osteoarthritis (in combination with boswellia, ashwagandha, and turmeric) Prostatitis (CBP, NBP) |
| Reliable
and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies
suggesting a health benefit or minimal health benefit. For an herb, supported by traditional use but minimal
or no scientific evidence. For a supplement, little scientific support and/or minimal health
benefit. |
|
Who is likely to be deficient?
Zinc deficiencies are quite common in people living in poor countries. Phytate, a substance found in unleavened bread (pita, matzos, and some crackers) significantly reduces absorption of zinc, increasing the chance of zinc deficiency. However, phytate-induced deficiency of zinc appears to be a significant problem only for people already consuming marginally low amounts of zinc.
Even in developed countries, low-income pregnant women and pregnant teenagers are at risk for marginal zinc deficiencies. Supplementing with 25–30 mg per day improves pregnancy outcome in these groups.1 2
People with liver cirrhosis appear to be commonly deficient in zinc.3 This deficiency may be due to cirrhosis-related zinc malabsorption.4
People with Down’s syndrome are also commonly deficient in zinc.5 Giving zinc supplements to children with Down’s syndrome has been reported to improve impaired immunity6 and thyroid function,7 though optimal intake of zinc for people with Down’s syndrome remains unclear.
Children with alopecia areata (patchy areas of hair loss) have been reported to be deficient in zinc.8 9
The average diet frequently provides less than the Recommended Dietary Allowance for zinc, particularly in vegetarians. To what extent (if any) these small deficits in zinc intake create clinical problems remains unclear. Nonetheless, a low-potency supplement (15 mg per day) can fill in dietary gaps. Zinc deficiencies are more common in alcoholics and people with sickle cell anemia, malabsorption problems, and chronic kidney disease.10
How much is usually taken?
Moderate intake of zinc, approximately 15 mg daily, is adequate to prevent deficiencies. Higher levels (up to 50 mg taken three times per day) are reserved for people with certain health conditions, under the supervision of a doctor. For the alleviation of cold symptoms, lozenges providing 13–25 mg of zinc in the form zinc gluconate, zinc gluconate-glycine, or zinc acetate are generally used frequently but only for several days.
Are there any side effects or interactions?
Zinc intake in excess of 300 mg per day has been reported to impair immune function.11 Some people report that zinc lozenges lead to stomach ache, nausea, mouth irritation, and a bad taste. One source reports that gastrointestinal upset, metallic taste in the mouth, blood in the urine, and lethargy can occur from chronic oral zinc supplementation over 150 mg per day,12 but those claims are unsubstantiated. In topical form, zinc has no known side effects when used as recommended. However, using zinc nasal spray has been reported to cause severe or complete loss of smell function in at least ten people. In some of those cases, the loss of smell was long-lasting or permanent.13
Preliminary research had suggested that people with Alzheimer’s disease should avoid zinc supplements.14 More recently, preliminary evidence in four patients actually showed improved mental function with zinc supplementation.15 In a convincing review of zinc/Alzheimer’s disease research, perhaps the most respected zinc researcher in the world concluded that zinc does not cause or exacerbate Alzheimer’s disease symptoms.16
Zinc inhibits copper absorption. Copper deficiency can result in anemia, lower levels of HDL (“good”) cholesterol, or cardiac arrhythmias.17 18 19 Copper intake should be increased if zinc supplementation continues for more than a few days (except for people with Wilson’s disease).20 Some sources recommend a 10:1 ratio of zinc to copper. Evidence suggests that no more that 2 mg of copper per day is needed to prevent zinc-induced copper deficiency. Many zinc supplements include copper in the formulation to prevent zinc-induced copper deficiency. Zinc-induced copper deficiency has been reported to cause reversible anemia and suppression of bone marrow.21
Marginal zinc deficiency may be a contributing factor in some cases of anemia. In a study of women with normocytic anemia (i.e., their red blood cells were of normal size) and low total iron-binding capacity (a blood test often used to assess the cause of anemia), combined iron and zinc supplementation significantly improved the anemia, whereas iron or zinc supplemented alone had only slight effects.22 Supplementation with zinc, or zinc and iron together, has been found to improve vitamin A status among children at high risk for deficiency of the three nutrients.23
Zinc competes for absorption with copper, iron,24 25 calcium,26 and magnesium.27 A multimineral supplement will help prevent mineral imbalances that can result from taking high amounts of zinc for extended periods of time.
N-acetyl cysteine (NAC) may increase urinary excretion of zinc.28 Long-term users of NAC may consider adding supplements of zinc and copper.
Are there any drug
interactions?
Certain medicines may interact with zinc. Refer to drug interactions for a list of those medicines.
1. Cherry FF, Sandstead HH, Rojas P, et al. Adolescent pregnancy: associations among body weight, zinc nutriture, and pregnancy outcome. Am J Clin Nutr 1989;50:945–54.
2. Goldenberg RL, Tamura T, Neggers Y, et al. The effect of zinc supplementation on pregnancy outcome. JAMA 1995;274:463–8.
3. Scholmerich J, Lohla E, Gerok W. Zinc and vitamin A deficiency in liver cirrhosis. Hepatogastroenterology 1983;30:119–25.
4. Karayalcin S, Arcasoy A, Uzunalimoglu O. Zinc plasma levels after oral zinc tolerance test in nonalcoholic cirrhosis. Dig Dis Sci 1988;33:1096–102.
5. Stabile A, Pesaresi MA, Stabile AM, et al. Immunodeficiency and plasma zinc levels in children with Down’s syndrome: a long-term follow-up of oral zinc supplementation. Clin Immunol Immunopathol 1991;58:207–16.
6. Björksten B, Back O, Gustavson KH, et al. Zinc and immune function in Down’s syndrome. Acta Paediatr Scand 1980;69:183–7.
7. Bucci I, Napolitano G, Guiliani C, et al. Zinc sulfate supplementation improves thyroid function in hypozincemic Down children. Biol Trace Elem Res 1999;67;257–68.
8. Wollowa F, Jablonska S. Zinc in the treatment of alopecia areata. In: Kobori Y, Montagna W (eds). Biology and Diseases of the Hair. Tokyo: University Park Press, 1976, 305.
9. Lutz G. The value of zinc in treatment of alopecia areata. 2nd Meeting of the European Hair Research Society, Bologna, April 14, 1991.
10. Prasad A. Discovery of human zinc deficiency and studies in an experimental human model. Am J Clin Nutr 1991;53:403–12 [review].
11. Chandra RK. Excessive intake of zinc impairs immune responses. JAMA 1984;252:1443.
12. Shannon M. Alternative medicines toxicology: a review of selected agents. Clin Toxicol 1999;37:709–13
13. Jafek BW, Linschoten MR, Murrow BW. Anosmia after intranasal zinc gluconate use. Am J Rhinol 2004;18:137–41.
14. Bush AI, Pettingell WH, Multhaup G, et al. Rapid induction of Alzheimer A8 amyloid formation by zinc. Science 1994;265:1464–5.
15. Potocnik FCV, van Rensburg SJ, Park C, et al. Zinc and platelet membrane microviscosity in Alzheimer’s disease. S Afr Med J 1997;87:1116–9.
16. Prasad AS. Zinc in human health: an update. J Trace Elem Exp Med 1998;11:63–87.
17. Broun ER, Greist A, Tricot G, Hoffman R. Excessive zinc ingestion-a reversible cause of sideroblastic anemia and bone marrow depression. JAMA 1990;264:1441–3.
18. Reiser S, Powell A, Yang CY, Canary JJ. Effect of copper intake on blood cholesterol and its lipoprotein distribution in men. Nutr Rep Int 1987;36:641–9.
19. Sandstead HH. Requirements and toxicity of essential trace elements, illustrated by zinc and copper. Am J Clin Nutr 1995;61(suppl):621S–24S [review].
20. Fischer PWF, Giroux A, Labbe MR. Effect of zinc supplementation on copper status in adult man. Am J Clin Nutr 1984;40:743–6.
21. Broun ER, Greist A, Tricot G, Hoffman R. Excessive zinc ingestion. A reversible cause of sideroblastic anemia and bone marrow depression. JAMA 1990;264:1441–3.
22. Nishiyama S, Irisa K, Matsubasa T, et al. Zinc status relates to hematological deficits in middle-aged women. J Am Coll Nutr 1998;17:291–5.
23. Muñoz EC, Rosado JL, Lopez P, et al. Iron and zinc supplementation improves indicators of vitamin A status of Mexican preschoolers. Am J Clin Nutr 2000;71:789–94.
24. Dawson EB, Albers J, McGanity WJ. Serum zinc changes due to iron supplementation in teen-age pregnancy. Am J Clin Nutr 1990;50:848–52.
25. Crofton RW, Gvozdanovic D, Gvozdanovic S, et al. Inorganic zinc and the intestinal absorption of ferrous iron. Am J Clin Nutr 1989;50:141–4.
26. Argiratos V, Samman S. The effect of calcium carbonate and calcium citrate on the absorption of zinc in healthy female subjects. Eur J Clin Nutr 1994;48:198–204.
27. Spencer H, Norris C, Williams D. Inhibitory effects of zinc on magnesium balance and magnesium absorption in man. J Am Coll Nutr 1994;13:479–84.
28. Brumas V, Hacht B, Filella M, Berthon G. Can N-acetyl-L-cysteine affect zinc metabolisms when used as a paracetamol antidote? Agents Actions 1992;36:278–88.
