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.
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) |
 |
Anaemia (for thallasaemia if deficient) Attention deficit–hyperactivity disorder (ADHD) Burns (zinc, copper, and selenium, intravenously, for extensive burns) Coeliac 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) Mouth ulcers (for deficiency only) 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 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 biscuits) 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 anaemia, 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 a few 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 gastro-intestinal 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 anaemia, 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 anaemia and suppression of bone marrow.21
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.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.
References
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Copyright © 2007 Healthnotes, Inc. All rights reserved. www.healthnotes.com
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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 September 2008.
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