Zinc
Research reviewed: up until 10/23
Zinc is a dietary supplement with 9 published peer-reviewed studies involving 1,321 participants, researched for Immunity/Common colds, COVID-19.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Immunity/Common colds
ModerateCOVID-19
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Immunity/Common colds
To determine the effect of preventative zinc sulphate syrup in reducing the occurrence of the common cold in children and to evaluate its effects on reducing the duration and severity of cold symptoms.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To determine the effect of preventative zinc sulphate syrup in reducing the occurrence of the common cold in children and to evaluate its effects on reducing the duration and severity of cold symptoms.
Dose
15 mg/day or 30 mg/day (2 x 15 mg syrup) of zinc or placebo Note: The dose was increased to 30 mg of zinc in children who exhibited at least two of the following 10 symptoms consistent with the common cold: cough, nasal drainage, nasal congestion, headache, hoarseness, muscle ache, itchy throat,sneezing, sore throat and fever. Children received medication two times per day until cold symptoms resolved, up to a maximum of 10 days.
Participants
200 healthy male and female children
Duration
7 months
Results
The study found that zinc sulphate syrup significantly reduced the occurrence of common cold in children, with the zinc group experiencing fewer colds compared to the placebo group. With zinc sulphate supplementation, 33% of the children did not experience any cold during the cold season, compared to 14% of the children taking placebo. The researchers also observed that the average number of colds in the zinc group was significantly fewer than in the placebo group (1.2 vs. 1.7 colds per child). In addition to shorter average cold symptoms duration (4.7 vs. 5.3 days), the zinc group also had a lower average cold-related school absence per child compared to the placebo group (0.9 vs. 1.3 days). Similarly, the duration of nasal symptoms was significantly shorter in the zinc group than in the placebo group (3.2 vs. 3.8 days). The duration of cough (2.9 vs. 3.2 days), sore throat (1.8 vs. 2.4 days), and itchy throat (0.1 vs. 0.3 days) was also shorter in the zinc group than in the placebo group. Moreover, the total symptom score was significantly lower in the zinc group compared to the placebo group, starting from the first day of the cold episode through day 7.
To investigate the effects of zinc supplementation in reducing the frequency rate and duration of common cold during cold season in school aged children living in a low socioeconomic suburb of Mashhad (Altimor), north‐east Iran.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate the effects of zinc supplementation in reducing the frequency rate and duration of common cold during cold season in school aged children living in a low socioeconomic suburb of Mashhad (Altimor), north‐east Iran.
Dose
10 mg of elemental zinc (taken daily 6 times a week) or placebo
Participants
200 male and female primary school children aged 78 to 120 months
Duration
5 months (November to March)
Results
Among the zinc-supplemented group, a common cold incidence of 1.73 episodes per child during the study period was recorded, compared to 3.15 cold episodes per child in the placebo group. The average overall missing days from school were 0.55 days and 1.35 days for the zinc-supplemented and placebo groups, respectively. The need for the administration of antibiotics for bacterial infections (pharyngitis, acute otitis media, sinusitis, pneumonia) was 20 courses for the zinc-supplemented group and 47 courses for the placebo group.
To investigate the effects of zinc gluconate lozenges in the treatment of common colds/
Study Type
Randomised, double-blind, placebo-controlled clinical trial
Purpose
To investigate the effects of zinc gluconate lozenges in the treatment of common colds/
Dose
23-mg zinc lozenge (dissolved in the mouth every 2 wakeful hours after an initial double dose) or matched placebo
Participants
65 male and female subjects who reported being ill for 3 days or less before starting the experiment with an average age of 36 (zinc group) and 28 years (placebo)
Duration
7 days
Results
In the group treated with zinc, a significant proportion of participants experienced a lack of symptoms within a short period of time (11% within 12 hours and 22% within 24 hours), while none of the participants treated with a placebo showed a lack of symptoms within 24 hours. By the end of the 7-day experiment, a notable 86% of zinc-treated individuals reported the absence of symptoms, while only 46% of those treated with a placebo made the same claim. Most symptoms associated with zinc treatment were mild and considered acceptable as part of the overall treatment. About half of the individuals who received zinc did not experience any adverse effects. Common objections were raised due to the unappealing taste, altered taste perception, and irritation of the oral cavity. An isolated case of a minor and temporary mouth lesion occurred when a subject kept a tablet in their mouth overnight. The emetic properties (induces vomiting) of zinc were observed in two subjects after the loading dose, and nausea occurred after the initial intake of a few tablets. However, it was noted that vomiting and nausea could be prevented by consuming food or drink before taking zinc.
How They Measured It
Presence and severity of common cold were self-recorded by the subjects using a report form. Symptoms were scored as being severe (3 points), moderate (2 points), minor (1 point), or absent (no points).
To test the effects of zinc acetate lozenges in reducing the duration of symptoms of the common cold.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To test the effects of zinc acetate lozenges in reducing the duration of symptoms of the common cold.
Dose
12.8 mg of zinc acetate per lozenge (taken every 2 to 3 hours while awake as long as the subjects had cold symptoms) or placebo
Participants
48 male and female volunteers recruited within 24 hours of developing symptoms of the common cold with an average age of 36 years (zinc group) and 38 years (placebo group)
Duration
12 days
Results
The researchers observed significant differences between the two study groups in the average duration of cold symptoms, with participants taking zinc lozenges experiencing 4.5 days of symptoms compared to 8.1 days of symptoms in those taking a placebo. Additionally, participants in the zinc group reported a significantly shorter duration of cough (3.1 days) and nasal discharge (4.1 days) compared to the placebo group (6.3 and 5.8 days, respectively). Fifty percent of participants in the zinc group recovered in 3.8 days, whereas it took 7.7 days for 50% of the placebo group to experience symptom improvement. At the start of the study, the average severity score was higher in the zinc group (10.8) than in the placebo group (8.9). However, by day 4, the average severity score in the zinc group was half that in the placebo group (2.7 vs. 5.4).
How They Measured It
Severity of symptoms and the medications taken throughout the duration of the cold were documented by the participants using a daily log. Every day, the participants graded each symptom as 0 for none, 1 for mild, 2 for moderate, and 3 for severe. Total symptom scores were calculated by summing the scores of the 10 symptoms for each day.
To investigate the effects of zinc on the average duration of cold symptoms.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate the effects of zinc on the average duration of cold symptoms.
Dose
13.3 mg of zinc acetate per lozenges (1 lozenge to be dissolved in the mouth every 2–3 hours while awake for as long as the participants had cold symptoms) or placebo
Participants
50 men and women with an average age of 35 years (zinc group) and 36 years (placebo group)
Duration
10 days
Results
The researchers found that the average duration of cold symptoms was shorter in the zinc group (4.0 days) compared to the placebo group (7.1 days). The cold was completely resolved in 56% of the zinc-group subjects, on day 4. On the other hand, no subject in the placebo group was free of cold symptoms on day 4. The participants in the zinc group also reported significantly shorter average durations of cough (2.2 days vs. 5.1 days), nasal discharge (3.0 days vs. 4.6 days), and muscle ache (0.8 days vs. 2.0 days) than in the placebo group. At the start of the study, the average severity scores for the zinc and placebo groups were 8.3 and 7.8, respectively; by day 4, these scores were 3.45 and 5.61, respectively.
How They Measured It
Cold symptoms were assessed using a daily log which documents the severity of the symptoms throughout the duration of the cold. Each symptom is graded as 0 for none, 1 for mild, 2 for moderate, or 3 for severe.
To assess the effects of zinc acetate lozenges on common cold symptoms in allergy-tested subjects.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To assess the effects of zinc acetate lozenges on common cold symptoms in allergy-tested subjects.
Dose
9 mg of zinc per lozenge or placebo Subjects were instructed to use a lozenge every 1.5 hours while awake during day 0, then one lozenge every 2 hours while awake on following days while symptoms were present. Lozenge consumption is stopped 6 hours after the symptoms stop.
Participants
102 male and female volunteers with an average age of 27 years and have two or more common cold symptom (101 completed the study)
Duration
14 days of using zinc lozenges or until the symptoms have stopped
Results
The researchers observed that the average duration of common cold symptoms was significantly shorter in the zinc group compared to the placebo group (3.8 days vs. 6.1 days). The average severity rating for all symptoms was also lower in the zinc group, however this difference was not statistically significant. Notably, allergy-positive individuals using zinc experienced a significantly shorter duration of nasal drainage symptoms (the flow or discharge of mucus from the nasal passage) compared to allergy-negative individuals (3.5 days vs. 7.6 days). Overall the researchers suggest that zinc acetate lozenges may significantly reduce the duration of common cold symptoms and alleviate symptoms associated with allergies.
How They Measured It
Severity of cold symptoms was assessed using a day in which the subjects rate and record their symptoms in a diary at the same time each day.
To investigate the effects of zinc gluconate - glycine lozenges in reducing the duration of common cold
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate the effects of zinc gluconate - glycine lozenges in reducing the duration of common cold
Dose
23.7 mg zinc in each 4.5 g lozenge (to suck, not chew, the lozenges as required but at not less than 2-h intervals taking up to a maximum of eight lozenges per day (189.6 mg/day)) or placebo
Participants
87 male and female participants aged 18 to 40 years (73 patients completed the study)
Duration
28 days
Results
The researchers observed a significant reduction in the average duration of the cold after treatment with zinc lozenges. The duration was 1.27 days less for the zinc group (4.86 days) compared to the placebo group (6.13 days). The researchers also observed that the rate at which patients taking zinc lozenges became symptom-free increased rapidly compared with the placebo-treated patients. In addition, the patients who received zinc treatment on day 1 (patients who had had symptoms for 1 calendar day prior to trial entry) had fewer and less severe symptoms compared to those who received treatment on day 2 (patients with symptoms for 2 calendar days prior to entry).
To test the efficacy of zinc gluconate lozenges in reducing the duration of symptoms caused by the common cold
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To test the efficacy of zinc gluconate lozenges in reducing the duration of symptoms caused by the common cold
Dose
13.3 mg of zinc (to dissolve 1 lozenge in the mouths every 2 hours while awake for as long as they had cold symptoms) or placebo (contained 5% calcium lactate pentahydrate)
Participants
99 men and women who developed symptoms of the common cold within 24 hours before enrollment with an average age of 38 years.
Duration
18 days
Results
The researchers observed that the duration of common cold symptoms was significantly shorter in the zinc group. The median time to resolution of all symptoms was 7.6 days in the placebo group while it took only 4.4 days in the zinc group. The zinc group also reported significantly fewer days with coughing, headache, hoarseness, nasal congestion, nasal drainage, and sore throat compared to the placebo group. However, the zinc group reported side effects per person (25 zinc recipients and 5 placebo recipients had two or more side effects), significantly more nausea (10 patients compared with 2 patients in the placebo), and more bad-taste reactions (39 patients compared with 15 patients in the placebo).
How They Measured It
The severity of cold symptoms and the medications taken throughout the duration of their cold were documented by the patients using a daily log, in which patients graded each symptom as 0 for none, 1 for mild, 2 for moderate, or 3 for severe.
COVID-19
To examine the effects of zinc in adults with COVID-19 infection
Study Type
Randomised, double-blind, controlled trial
Purpose
To examine the effects of zinc in adults with COVID-19 infection
Dose
50 mg/day of zinc (2 x 25 mg capsules) or placebo
Participants
470 male and female COVID-19 patients with an average age of 54 years
Duration
15 days
Results
The study reported 37 overall deaths, with 30 (81.1%) occurring in the ICU and 7 (18.9%) outside the ICU. The death rate at 30 days was 6.5% (15 patients) in the zinc group compared to 9.2% (22 patients) in the placebo group, and the ICU admission rates were 5.2% (12 patients) and 11.3% (27 patients) respectively. In addition, the length of hospital stay was shorter in the zinc group compared to the placebo group, and the duration of COVID-19 symptoms was also reduced relatively with zinc treatment. Further analysis showed an association between zinc and positive effects in inpatients, patients aged over 65 years, patients with comorbidities, and those requiring oxygen at the beginning of the study. For inpatients, although the risk of death among patients receiving zinc and placebo was similar, the absolute risk reduction in ICU admission was approximately 10% and the length of hospital stay was reduced by 3 days. These findings imply that, for survivors, the course of the disease appears less severe among patients in the zinc group, leading to a decreased requirement for hospital care and organ support. No severe adverse events were observed during the study.
Frequently Asked Questions
Common questions about Zinc research
There are currently 9 peer-reviewed studies on Zinc, involving 1,321 total participants. Research covers Immunity/Common colds, COVID-19. The overall evidence strength is rated as Strong.
The evidence is currently rated as "Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (9 human studies), and reported outcomes.
Zinc has been researched for: Immunity/Common colds, COVID-19. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 9 out of 9 studies are human trials. Human trials carry more weight in our evidence scoring system.
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