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ZINC
Food
Sources
Good sources of zinc include oysters, meat, eggs, seafood, black-eyed
peas, tofu, and wheat germ.
Deficiency
Risk and Symptoms
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.9 10
The average
diet frequently provides less than the recommended daily allowance for
zinc. A low-dose supplement (15 mg per day) can fill in dietary gaps. Zinc
deficiencies are more common in alcoholics and individuals with sickle
cell anemia, malabsorption problems, and chronic kidney disease.11
Benefit
in Diabetes: It has been shown that individuals with diabetes
have impaired intestinal zinc absorption and low plasma zinc levels. Zinc
supplements have the potential to help individuals with hypoglycemia, IGT,
and diabetes.
Recommended Dosage
Moderate intake of zinc, 15–25 mg, is adequate to prevent deficiencies.
Higher levels (up to 50 mg TID) are reserved for treating certain health
conditions, under the supervision of a doctor. For the alleviation of cold
symptoms, lozenges providing 15–25 mg of zinc in the form zinc gluconate
are generally used frequently throughout the day.
Contraindications
Zinc intake in excess of 300 mg per day has been reported to impair immune
function.12 Some people report that zinc lozenges lead
to stomachache, nausea, mouth irritation, and a bad taste. In topical
form, zinc has no known side effects when used as recommended.
Harmful Effects: No
harmful side effects. Medication may need to be adjusted based on glucose
lowering effect
Preliminary
research had suggested that people with Alzheimer’s
disease should avoid zinc supplements.13 More recently,
preliminary evidence in four patients actually showed improved mental
function with zinc supplementation.14 In a convincing review of
the 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.15
Zinc inhibits copper
absorption, which can lead to anemia and lower levels of HDL cholesterol
(the “good” cholesterol).16 17 18 Copper intake should be
increased if zinc supplementation continues for more than a few days
(except for individuals with Wilson’s
disease).19 Many zinc supplements, to prevent copper
inhibition, include copper in the formulation.
Zinc competes
for absorption with iron,20 21
calcium,22 and magnesium.23
A multimineral supplement will
prevent mineral imbalances that can result from taking high doses of zinc
for extended periods of time.
N-acetyl
cysteine, (NAC) may increase urinary excretion of zinc.24
Long-term users of NAC may consider adding supplements of zinc and copper.
References:
1. Mossad SB,
Macknin ML, Medendorp SV, et al. Zinc gluconate lozenges for treating the
common cold. Ann Int 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 Pharmacolther 1998;32:63–9 [review].
7. Petrus EJ, Lawson KA, Bucci LR, Blum K. Randomized, double-masked,
placebo-controlled clinical study of the effectiveness of zinc acetate
lozenges on common cold symptoms in allergy-tested subjects. Curr Ther
Res 1998;59:595–607.
8. 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.
9. 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.
10. Goldenberg RL, Tamura T, Neggers Y, et al. The effect of zinc
supplementation on pregnancy outcome. JAMA 1995;274:463–8.
11. Prasad A. Discovery of human zinc deficiency and studies in an
experimental human model. Am J Clin Nutr 1991;53:403–12 [review].
12. Chandra RK. Excessive intake of zinc impairs immune responses. JAMA
1984;252(11):1443.
13. Bush AI, Pettingell WH, Multhaup G, et al. Rapid induction of
Alzheimer A8 amyloid formation by zinc. Science 1994;265:1464–5.
14. 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.
15. Prasad AS. Zinc in human health: an update. J Trace Elements Exper
Med 1998;11:63–87.
16. 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.
17. Resiser S, et al. Effect of copper intake on blood cholesterol and its
lipoprotein distribution in men. Nutr Rep Internat
1987;36(3):641–9.
18. Sandstead HH. Requirements and toxicity of essential trace elements,
illustrated by zinc and copper. Am J Clin Nutr
1995;61(suppl):621S–24S [review].
19. Fischer PWF, Giroux A, Labbe MR. Effect of zinc supplementation on
copper status in adult man. Am J Clin Nutr 1984;40(4):743–6.
20. 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.
21. 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.
22. 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.
23. 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.
24. 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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