Zinc and Its Uses
Upon completion of this activity, participants will be able to:
1. List conditions for which zinc supplementation may be therapeutic
2. Describe the effect of zinc supplementation in children from developing countries who
have acute or chronic diarrhea
3. Describe the potential uses of oral zinc supplementation in elderly patients
4. Describe the evidence for the use of zinc supplements in the prevention and treatment of
upper viral respiratory tract infection or the common cold
Case 1
A 45-year-old healthy, active man has a body mass index of 26 kg/m² and a daily intake of a
balanced 2500-kcal diet. He has recurrent mouth sores and is concerned that he may be zincdeficient. He is also worried that such a deficiency may predispose him to leg ulcers, infections,
and other diseases. What might be an appropriate response to his concerns?
Case 2
Mrs. X is a healthy 35-year-old mother of 2 young children and works as a full-time receptionist in a
medical office. The children attend daycare. Over the past winter she has experienced several
episodes of viral upper respiratory infection, which she attributes to the common cold. These
episodes have not required antibiotics for management but she had missed 4 days of work
because of them. She has heard that echinacea or zinc supplementation may be helpful in
preventing or shortening the course of viral upper respiratory infections. How would you advise
her?
Commentary
Diverse Uses and Preparations of Zinc
In the United States, zinc is available over the counter in several oral formulations, such as zinc
acetate, zinc citrate, zinc gluconate, and zinc oxide. It is useful for the treatment and prevention of
zinc deficiency, and it is also taken for treating and/or preventing many conditions, including the
common cold, recurrent ear infections, asthma, lower respiratory tract infections, macular
degeneration, night blindness, cataracts, psoriasis, eczema, and acne. [1] Although no strong
evidence supports its benefit for the majority of these problems, some studies have been positive
for certain conditions. In particular, use of zinc for deficiency conditions related to malnutrition,
diarrhea, and parenteral nutrition has good rationale and supportive evidence. The use of zinc
supplementation has been shown to benefit age-related macular degeneration. For example, in
the Age-Related Eye Disease Study (AREDS), taking daily oral elemental zinc (80 mg), vitamin C
(500 mg), vitamin E (400 IU), and beta-carotene (15 mg) daily was associated with a risk reduction
of 27% for visual acuity loss and of 24% for progression of advanced age-related macular
degeneration.[2]
Other forms of zinc have been used for the following conditions:
 Topical zinc for acne, aging skin, herpes simplex infections, and wound healing;
 Zinc citrate in toothpaste and mouthwash to prevent dental plaque and gingivitis;
 Zinc nasal spray and nasal gel for shortening the duration of the common cold; and
 Parenteral zinc for total parenteral nutrition and for improving outcomes in burn patients.
Upper Limit Dosages for Zinc and Potential Toxicity
The upper tolerable recommended dose of oral zinc in adults is 40 mg/day (Table 1); higher levels
have been associated with a decrease in copper absorption, resulting in anemia. [3] Intranasal zinc
may be associated with anosmia, as demonstrated in the mouse model, and caution is
recommended in its use.[4-6] Chronic intake of zinc at levels of over 450 mg daily can cause
sideroblastic anemia, while a 10- to 30-g intake of zinc sulfate can be lethal in adults.[3] Zinc is
found in many foods that are part of normal diets, including fortified cereal, meat, poultry, and
whole grains. Anyone considering taking a zinc supplement should first consider whether their
needs could be met by these dietary zinc sources.
Table 1. Upper Levels for Zinc for Infants, Children, and Adults
Age
Infants and Children Males and Females Pregnancy and Lactation
0 to 6 months
4 mg
7 to 12 months 5 mg
1 to 3 years
7 mg
4 to 8 years
12 mg
9 to 13 years
23 mg
14 to 18 years 34 mg
Ages 19+
34 mg
40 mg
40 mg
From: Facts About Dietary Supplements. National Institutes of Health, Office of Dietary
Supplements. Available at: http://ods.od.nih.gov/factsheets/cc/zinc.html#rda
Zinc Deficiency and the US RDA
Zinc deficiency requiring supplementation may occur in severe diarrhea; liver cirrhosis; with longterm total parenteral nutrition; and with malabsorption after major surgery from intestinal disorders
such as Crohn's disease, sprue, and short bowel syndrome. Vegetarians may need as much as
50% more zinc than non-vegetarians because of the lower absorption of zinc from plant foods.[7]
People with alcoholism are also at high risk for deficiencies.[8] In a healthy person consuming the
US recommended daily allowance (RDA) (Table 2) with appropriate total energy intake, zinc
deficiency is unlikely. (For dietary sources of zinc, see the food composition database at:
http://www.nal.usda.gov/fnic/etext/000020.html)
Table 2. US Recommended Daily Allowances for Zinc for Infants Over 7 Months, Children,
and Adults
Age
Infants and Children Males Females Pregnancy Lactation
7 months to 3 years 3 mg
4 to 8 years
5 mg
9 to 13 years
8 mg
14 to 18 years
11 mg 9 mg
13 mg
14 mg
19+
11 mg 8 mg
11 mg
12 mg
Results of 2 national surveys, the National Health and Nutrition Examination Survey (NHANES III
1988-91) and the Continuing Survey of Food Intakes of Individuals (1994 CSFII), indicated that
most infants, children, and adults consume recommended amounts of zinc.
From: Facts About Dietary Supplements. National Institutes of Health, Office of Dietary
Supplements. Available at: http://ods.od.nih.gov/factsheets/cc/zinc.html#rda
Effects of Zinc Supplementation for Specific Conditions
Zinc supplementation in severe diarrhea. Zinc supplementation in children with acute and
severe diarrhea has been associated with reduced child mortality in studies conducted in
developing countries,[9] and zinc supplementation in this population can also reduce the probability
of continuing diarrhea by 24% in acute diarrhea and 42% in persistent diarrhea.[10]
Zinc and the elderly. Small trials have shown a benefit of oral zinc supplementation in reducing
the incidence of infections in elderly patients, in whom cell-mediated immune dysfunction and
increased oxidative stress may contribute to susceptibility to infection and relative zinc deficiency
compared with younger patients.[10-12] Oral zinc supplementation has not been shown to be
beneficial in the healing of leg ulcers even in patients considered to be malnourished, according
to a recent Cochrane review.[13]
Topical zinc for herpes simplex Applying zinc topically has been shown to benefit perioral
herpes simplex virus (HSV) infection, and zinc sulfate has been shown to reduce the severity and
duration of both orolabial and genital HSV.[14] In particular, a specific formulation of l-lysine, zinc
oxide, and 14 other ingredients was shown to decrease symptom severity and duration when
applied every 2 hours.[15]
Zinc and the common cold. Studies have addressed the potential use of zinc for preventing or
shortening the duration of the common cold or viral upper respiratory infection. A recent Cochrane
review of studies conducted from 1984 to 1997[16] suggested that the use of zinc lozenges for cold
symptoms was inconclusive. However, a comprehensive review of studies from 1980 to 2003 [17]
examining multiple formulations of zinc supplementation, including tablets, lozenges, and
intranasal preparations in randomized, double-blind, placebo-controlled studies, suggested that
inconsistent results are likely due to varying formulations used. Furthermore, it found 2 welldesigned trials providing good evidence that zinc gluconate administered within 24 hours of
symptom onset can reduce the duration of the common cold. Zinc formulations for the common
cold have not been systematically studied in pregnant and lactating women. A recent study
conducted in children suggested that current data are inadequate to support the use of zinc for the
prevention or treatment of the common cold in children.[18]
More recently, credence has been given to a nasal gel formulation for treatment of the common
cold[19] with a total dose of 2.1 mg daily shortening the duration of common cold symptoms if
started within 24 hours of symptom onset. The duration of symptoms was reduced to 2.3 days
compared with placebo, with a duration of 9.0 days for respiratory symptoms in a randomized trial
conducted in 213 adults.[20] However concerns about anosmia or hyposmia remain, as reported in
a retrospective report of patients who inhaled deeply when applying the nasal gel.[21]
Responses to Cases
Response to Case 1
In a healthy well-nourished man, zinc deficiency is unlikely and zinc supplementation is not
indicated in this patient. He is unlikely to be at risk for leg ulcers from zinc deficiency, given his
nutritional status and young age. A diagnosis of the cause of recurrent oral sores would be helpful
in future management of this condition. Swabs for viral culture during an attack may be helpful in
diagnosis and in ruling out oral HSV, for which appropriate treatment should be offered. If swabs
are negative for HSV, topical zinc may be considered to hasten recovery and response time should
be documented for decisions about future use.
Response to Case 2
The evidence for the efficacy of zinc for the prevention and treatment of the common cold is still
controversial. There is no evidence of adverse effects when zinc is taken in appropriate doses of
no more than 40 mg daily orally. Among the preparations available over the counter, zinc gluconate
lozenges have been associated with shortening the duration of the common cold and could be
recommended on a trial basis for this patient, to be taken within 24 hours of onset of cold
symptoms. Zinc nasal gel also has been shown to reduce the duration of cold symptoms, but the
patient should be warned not to inhale deeply due to concerns about a possible adverse effect of
anosmia or hyposmia. Duration and severity of upper respiratory infections over the period of zinc
therapy should be monitored to track efficacy.
NOW TEST YOUSELF!
1
According to the literature, topical zinc has been found to be potentially helpful for all the
following conditions except:
A
Acne
B
Macular degeneration
C
Aging skin
D
Wound healing
2.
According to studies conducted in developing countries, the use of zinc in acute diarrhea
may be associated with a reduction in incidence of continuing diarrhea up to _____.
A
10%
B
24%
C
42%
D
60%
3.
An 85-year-old woman in a convalescent home is malnourished with episodes of recurrent
upper respiratory infections over the past 6 months. Full blood count and metabolic panel
are normal and a screen for occult cancer is negative. According to current evidence, oral
zinc supplementation is most likely to be helpful for her in which one of the following
conditions?
A
Leg ulcers
B
Recurrent infections
C
Acute diarrhea
D
Chronic diarrhea
4.
According to current evidence on use of zinc for the common cold, which one of the
following outcomes is most likely to be improved by the use of zinc nasal gel?
A
Duration of cold symptoms
B
Severity of cold symptoms
C
Prevention of cold symptoms
D
Prevention of progression to lower respiratory infection