|
Zinc: What does it do?
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.
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.
reduces the body’s ability to utilize 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.
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 diarrhea 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 sulfate 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 sulfate) three times daily, for one month. 73% of those taking the
zinc sulfate 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.
Who is likely to be deficient of 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.
deficiencies are more common in alcoholics and
people with sickle cell anemia, malabsorption problems, and chronic kidney
disease.21
How much Zinc 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 with 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.
Preliminary research had suggested that people with Alzheimer’s disease should avoid zinc
supplements.24 More recently, preliminary evidence in four patients actually showed
improved mental function with zinc supplementation.25 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.26
inhibits copper absorption. Copper
deficiency can result in anemia, lower levels of HDL (“good”) cholesterol, or cardiac arrhythmias.27 28
29 Copper intake should be increased if zinc supplementation continues for more than a
few days (except for people with Wilson’s
disease).30 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. -induced copper deficiency has been reported to cause reversible anemia
and suppression of bone marrow.31
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.32 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.33
competes for absorption with copper,
iron,34 35 calcium,36 and magnesium.37 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.38 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.
SHOP For Zinc By Category
Like eVitamins? Become A Fan Today!
Copyright © 2004 Healthnotes, Inc. All rights reserved.
www.healthnotes.com
Learn more
about Healthnotes, the company.
Learn more
about the authors of Healthnotes.
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
pharmacist for any health problem and before using any supplements or before
making any changes in prescribed medications.
References:
Click
here to view references
| 
Cart: 0 items 
Checkout
