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
People with liver cirrhosis appear to be
commonly deficient in zinc.3 This deficiency may be due to cirrhosis-related zinc
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
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
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
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
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
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
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.
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
16. Prasad AS. Zinc in human health: an update. J Trace Elem Exp
17. Broun ER, Greist A, Tricot G, Hoffman R. Excessive zinc ingestion-a
reversible cause of sideroblastic anemia and bone marrow depression. JAMA
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
19. Sandstead HH. Requirements and toxicity of essential trace elements,
illustrated by zinc and copper. Am J Clin Nutr 1995;61(suppl):621S–24S
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
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
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
27. Spencer H, Norris C, Williams D. Inhibitory effects of zinc on
magnesium balance and magnesium absorption in man. J Am Coll Nutr
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