Zinc

What is it?

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, synthesise protein, help cells reproduce, preserve vision, boost immunity, and protect against free radicals, among other functions.

In double-blind trials, zinc lozenges have reduced the duration of colds in adults,¹ ² ³ but have been ineffective in children.⁴ The ability of zinc to shorten colds may be due to a direct, localized anti-viral action in the throat. For the alleviation of cold symptoms, lozenges providing 13–25 mg of zinc, in the form of zinc gluconate, zinc gluconate-glycine, or zinc acetate, are used, typically every two hours while awake, but only for several days. The best effect is obtained when lozenges are used at the first sign of a cold.

Lozenges containing zinc gluconate, zinc gluconate-glycine, or zinc acetate have been effective, whereas most other forms of zinc and lozenges flavored with citric acid,⁵ tartaric acid, sorbitol, or mannitol, have been ineffective.⁶ Trials using forms other than zinc gluconate, zinc gluconate-glycine, or zinc acetate have failed, as have trials that use insufficient amounts of zinc.⁷ Therefore, until more is known, people should only use zinc gluconate, zinc gluconate-glycine, or zinc acetate.

Zinc reduces the body’s ability to utilise the essential mineral copper. (For healthy people, this interference is circumvented by supplementing with copper, along with zinc.) The ability to interfere with copper makes zinc an important therapeutic tool for people with Wilson’s disease—a genetic condition that causes copper overload.

Zinc supplementation in children in developing countries is associated with improvements in stunted growth, increased weight gain in underweight children, and substantial reductions in the rates of diarrhoea and pneumonia, the two leading causes of death in these settings.⁸ ⁹ ¹⁰ Whether such supplementation would help people in better nourished populations remains unclear.

A small, preliminary trial has found zinc sulphate to be effective for contact dermatitis (a skin rash caused by contact with an allergen or irritant).¹¹ Participants with active skin rashes took approximately 23 mg of zinc (in the form of zinc sulphate) three times daily, for one month. 73% of those taking the zinc sulphate had complete resolution of their skin rashes, while the remaining participants had a 50–75% improvement. Further trials are needed to confirm these preliminary findings, however.

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
	Acne Acrodermatitis enteropathica Childhood intelligence (for deficiency) Common cold/sore throat (as lozenges) Down’s syndrome Infertility (male) (for deficiency) Night blindness (for deficiency) Wilson’s disease Wound healing (oral and topical)
	Anaemia (for thallasaemia if deficient) Anorexia nervosa Attention deficit–hyperactivity disorder Birth defects prevention Coeliac disease (for deficiency) Cold sores (topical) Common cold (as nasal spray) Crohn’s disease Genital herpes Gingivitis (zinc plus bloodroot toothpaste) Halitosis (zinc chloride rinse or toothpaste) Hepatitis C (zinc-L-carnosine) HIV support Immune function (for elderly people) Infection Liver cirrhosis (for deficiency) Macular degeneration Mouth ulcers (for deficiency only) Peptic ulcer Pregnancy support Rheumatoid arthritis Sickle cell anaemia Skin ulcers (oral and topical zinc) Sprains and strains (if deficient) Tinnitus (for deficiency only) Type 1 diabetes Type 2 diabetes (preferably for those with a documented deficiency) Warts
	Amenorrhoea Athletic performance Benign prostatic hyperplasia (BPH) Contact dermatitis Cystic fibrosis Dermatitis herpetiformis (for deficiency) Diarrhoea Ear infections (recurrent) Gastritis Gestational hypertension Goitre Hypoglycaemia Hypothyroidism Immune function (for non-elderly people) Insulin resistance syndrome (Syndrome X) Osgood-Schlatter Disease Osteoarthritis (in combination with boswellia, ashwagandha, and turmeric) Osteoporosis Pre- and post-surgery health Preeclampsia 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 a 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.¹² ¹³

People with liver cirrhosis appear to be commonly deficient in zinc.¹⁴ This deficiency may be due to cirrhosis-related zinc malabsorption.¹⁵

People with Down’s syndrome are also commonly deficient in zinc.¹⁶ Giving zinc supplements to children with Down’s syndrome has been reported to improve impaired immunity¹⁷ and thyroid function,¹⁸ 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.¹⁹ ²⁰

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 anaemia, malabsorption problems, and chronic kidney disease.²¹

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.²² 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,²³ 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.²⁴

Preliminary research had suggested that people with Alzheimer’s disease should avoid zinc supplements.²⁵ More recently, preliminary evidence in four patients actually showed improved mental function with zinc supplementation.²⁶ 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.²⁷

Zinc inhibits copper absorption. Copper deficiency can result in anaemia, lower levels of HDL (“good”) cholesterol, or cardiac arrhythmias.²⁸ ²⁹ ³⁰ Copper intake should be increased if zinc supplementation continues for more than a few days (except for people with Wilson’s disease).³¹ 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 anaemia and suppression of bone marrow.³²

Marginal zinc deficiency may be a contributing factor in some cases of anaemia. In a study of women with normocytic anaemia (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 anaemia), combined iron and zinc supplementation significantly improved the anaemia, whereas iron or zinc supplemented alone had only slight effects.³³ 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.³⁴

Zinc competes for absorption with copper, iron,³⁵ ³⁶ calcium,³⁷ and magnesium.³⁸ 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.³⁹ 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.

References
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1. Mossad SB, Macknin ML, Medendorp SV, et al. Zinc gluconate lozenges for treating the common cold. Ann Intern Med 1996;125:81–8.

2. Anonymous. Zinc lozenges reduce the duration of common cold symptoms. Nutr Rev 1997;55:82–8 [review].

3. Garland ML, Hagmeyer KO. The role of zinc lozenges in treatment of the common cold. Ann Pharmacother 1998;32:93–69 [review].

4. Macknin ML, Piedmonte M, Calendine C, et al. Zinc gluconate lozenges for treating the common cold in children. A randomized controlled trial. JAMA 1998;279:1962–7.

5. Eby G. Where’s the bias? Ann Intern Med 1998;128:75 [letter].

6. Garland ML, Hagmeyer KO. The role of zinc lozenges in treatment of the common cold. Ann Pharmacother 1998;32:63–9 [review].

7. Weismann K, Jakobsen JP, Weismann JE, et al. Zinc gluconate lozenges for common cold. A double-blind clinical trial. Dan Med Bull 1990;37:279–81.

8. Bhutta ZA, Black RE, Brown KH, et al. Prevention of diarrhea and pneumonia by zinc supplementation in children in developing countries: pooled analysis of randomized controlled trials. Zinc Investigators’ Collaborative Group. J Pediatr 1999;135:689–97.

9. Umeta M, West CE, Haidar J, et al. Zinc supplementation and stunted infants in Ethiopia: a randomised controlled trial. Lancet 2000;355:2021–6.

10. Gibson RS. Zinc supplementation for infants. Lancet 2000;355:2008–9.

11. Santucci B, Cristaudo A, Mehraban M, et al. ZnSO4 treatment of NiSO4-positive patients. Contact Dermatitis 1999;40:281–2.

12. 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.

13. Goldenberg RL, Tamura T, Neggers Y, et al. The effect of zinc supplementation on pregnancy outcome. JAMA 1995;274:463–8.

14. Scholmerich J, Lohla E, Gerok W. Zinc and vitamin A deficiency in liver cirrhosis. Hepatogastroenterology 1983;30:119–25.

15. Karayalcin S, Arcasoy A, Uzunalimoglu O. Zinc plasma levels after oral zinc tolerance test in nonalcoholic cirrhosis. Dig Dis Sci 1988;33:1096–102.

16. 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.

17. Björksten B, Back O, Gustavson KH, et al. Zinc and immune function in Down’s syndrome. Acta Paediatr Scand 1980;69:183–7.

18. 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.

19. 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.

20. Lutz G. The value of zinc in treatment of alopecia areata. 2nd Meeting of the European Hair Research Society, Bologna, April 14, 1991.

21. Prasad A. Discovery of human zinc deficiency and studies in an experimental human model. Am J Clin Nutr 1991;53:403–12 [review].

22. Chandra RK. Excessive intake of zinc impairs immune responses. JAMA 1984;252:1443.

23. Shannon M. Alternative medicines toxicology: a review of selected agents. Clin Toxicol 1999;37:709–13

24. Jafek BW, Linschoten MR, Murrow BW. Anosmia after intranasal zinc gluconate use. Am J Rhinol 2004;18:137–41.

25. Bush AI, Pettingell WH, Multhaup G, et al. Rapid induction of Alzheimer A8 amyloid formation by zinc. Science 1994;265:1464–5.

26. 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.

27. Prasad AS. Zinc in human health: an update. J Trace Elem Exp Med 1998;11:63–87.

28. 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.

29. 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.

30. Sandstead HH. Requirements and toxicity of essential trace elements, illustrated by zinc and copper. Am J Clin Nutr 1995;61(suppl):621S–24S [review].

31. Fischer PWF, Giroux A, Labbe MR. Effect of zinc supplementation on copper status in adult man. Am J Clin Nutr 1984;40:743–6.

32. 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.

33. 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.

34. 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.

35. 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.

36. 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.

37. 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.

38. 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.

39. 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.

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or chemist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2007.

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