Clinical Question:

It’s winter and you’re working in a family practice office. Many pts are coming in with runny noses and general malaise. Brenda, a 35 yr old working mom comes in for a checkup and says “I’m so busy between work and home that I definitely don’t have time to get sick! Can those zinc or vitamin c pills I hear abt prevent colds?”

PICO Question:

Does the use of zinc or vitamin c pills help prevent the common cold in adults, during the winter?

Search Strategy:

Outline the terms used, databases  or other tools used, how many articles returned, and how  you selected the final articles to base your CAT on

  1. PubMed

2. Google Scholar

3. CUNY OneSearch

Articles Chosen for Inclusion (please copy and paste the abstract with link):

1.Abstract: The common cold had resulted in significant economic and social burden worldwide. The effect of vitamin C on preventing common cold in healthy adults has been investigated extensively, but not that of other micronutrients. Thus, we aim to assess the effects of providing micronutrients singly through oral means, on cold incidence, and/or management (in terms of cold duration and symptom severity) in healthy adults from systematically searched randomized controlled trials. From four electronic databases, 660 identified studies were screened and data were extracted from 20 studies (zinc, 10; vitamin D, 8; and vitamins A and E, 2). The quality of selected studies was assessed using the Cochrane risk of bias tool and certainty in the outcomes was assessed with the Grading of Recommendations Assessment, Development and Evaluation approach. The review found that micronutrients supplementation, except vitamin C, may not prevent cold incidence or reduce symptom severity among healthy adults. However, zinc supplementation was observed to potentially reduce cold duration by 2.25 days (when zinc is provided singly, 95% CI: −3.39, −1.12). This suggests that zinc supplementation may reduce the overall burden due to common cold among healthy adults.

2. Abstract in English, Translated from Spanish

Introduction: The common cold is one of the most common diseases. It is generally believed that the consumption of vitamin C prevents its appearance, but the actual efficacy of this measure is controversial.

Methods: To answer this question we used Epistemonikos, the largest database of systematic reviews in health, which is maintained by screening multiple information sources, including MEDLINE, EMBASE, Cochrane, among others. We extracted data from the systematic reviews, reanalyzed data of primary studies, conducted a meta-analysis and generated a summary of findings table using the GRADE approach.

Results and conclusions: We identified eight systematic reviews including 45 studies overall, of which 31 were randomized trials. We concluded the consumption of vitamin C does not prevent the incidence of common cold.

3. Abstract:The early indications of vitamin C deficiency are unremarkable (fatigue, malaise, depression) and may manifest as a reduced desire to be physically active; moreover, hypovitaminosis C may be associated with increased cold duration and severity. This study examined the impact of vitamin C on physical activity and respiratory tract infections during the peak of the cold season. Healthy non-smoking adult men (18–35 years; BMI < 34 kg/m2; plasma vitamin C < 45 µmol/L) received either 1000 mg of vitamin C daily (n = 15) or placebo (n = 13) in a randomized, double-blind, eight-week trial. All participants completed the Wisconsin Upper Respiratory Symptom Survey-21 daily and the Godin Leisure-Time Exercise Questionnaire weekly. In the final two weeks of the trial, the physical activity score rose modestly for the vitamin C group vs. placebo after adjusting for baseline values: +39.6% (95% CI [−4.5,83.7]; p = 0.10). The number of participants reporting cold episodes was 7 and 11 for the vitamin C and placebo groups respectively during the eight-week trial (RR = 0.55; 95% CI [0.33,0.94]; p = 0.04) and cold duration was reduced 59% in the vitamin C versus placebo groups (−3.2 days; 95% CI [−7.0,0.6]; p = 0.06). These data suggest measurable health advantages associated with vitamin C supplementation in a population with adequate-to-low vitamin C status.

Summary of the Evidence:

Author (Date)Sample/Setting(# of subjects/ studies, cohort definition etc. )Level of EvidenceOutcome(s) studiedKey FindingsLimitations and Biases
Min Xian Wang, Shwe Sin Win, Junxiong Pang (July, 2020)660 identified studies were screened and data were extracted from 20 studies (zinc, 10; vitamin D, 8; and vitamins A and E, 2). The quality of selected studies was assessed using the Cochrane risk of bias tool and certainty in the outcomes was assessed with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.Systematic Review Outcome of micronutrients (other than vitamin C) on the common cold- including prevention, duration of symptoms and severity of symptoms. We specifically focused on the effects of zinc. – When it comes to cold prevention zinc has proven to be effective in children, but not adults likely due to the fact that zinc helps boost the immune system and adults have a more robust immune system so zinc proves to be not helpful in preventing a cold, no matter how high the dose is.- Zinc deficiency has been associated with immunodeficiency so supplementing zinc in someone with low zinc may be helpful in preventing colds. But if someone isnt low in zinc it wont help.- The balance of how much zinc to take is very fine- too much may cause immunodeficiency, too little may not be helpful.- give zinc within 24 hrs of symptoms for max benefit, and efficacy varies with the type of zinc. Zinc gluconate is best at replicating zinc ions and preventing colds. – Use of zinc seems to decrease severity and length of cold. – Low external validity- May not be able to apply these findings to combo vitamins including multiple micronutrients, or to non-oral routes of these substances. – Only studied in western population and we dont know how it will be in Asian population or tropical countries. – Cold severity was self reported, and even though some severity tools were used there could still be bias (not as good if there was clinical testing)- There is a small amount of studies included in the review so there may be publication bias (where they only include what they want to talk abt).
Evelyn Gómez, Sebastián Quidel, Gonzalo Bravo-Soto, Ángela Ortigoza (August, 2018)8472 patients in total from 18 RCTs from Epistemonikos which screened multiple sources like MEDLINE, EMBASE, Cochrane, and others unspecified. Followed the GRADE approach to rate the certainty of evidence. Meta – AnalysisAll trials evaluated supplementation with oral doses higher than 0.08 g/day of vitamin C and the incidence, duration, and severity of the cold, among others. The follow-up period ranged from 3 weeks to 36 weeks. The consumption of vitamin C does not prevent the incidence of common cold with High certainty of evidence based on GRADE.Trials did not evaluate patients with specific comorbidities.
Does not apply to high performance athletes or other people subjected to major physical stress, considered a different population.
Trials did not report the season in which they were conducted and did not provide a clear definition of common cold.
Did not declare relevant interests for potential conflicts of interest.
Jennifer Hunter et al., 202128 RCTs with a total of 5,446 participants. Conducted in various settings and populations, including adults at risk of viral respiratory tract infections.Systematic review and meta-analysisOutcome evaluated the benefits and risks of zinc formulations compared with controls for the prevention or treatment of acute viral respiratory tract infections in adults. The outcomes studied included the incidence of respiratory tract infections, symptomatic survival, composite symptom severity scores, health-related quality of life (QoL), and serious and non-serious adverse events (AEs).Zinc, when used for prophylaxis, was associated with a lower risk of contracting a clinical illness consistent with a community-acquired viral respiratory tract ]]-infection compared to a placebo. Zinc, when used for treatment, was found to shorten the duration of symptoms and reduce day 3 symptomatic severity. However, it did not significantly impact overall daily symptom severity. Zinc was associated with an increased risk of non-serious adverse events (e.g., nausea, mouth/nasal irritation), which may limit its tolerability for some individuals.No serious adverse events were reported in the 25 RCTs that monitored them.The study found high bias risk,
It couldn’t answer questions about zinc formulations and doses, and results may not apply to zinc-deficient populations. Rapid review methods increased the risk of selective reporting bias. Calibration discrepancies led to changes in the review process.
The study found high risk of bias in RCTs, including randomization, blinding, selective outcome reporting, and potential conflicts of interest. Rapid review methods may introduce biases. Although it provides valuable insights into zinc’s benefits and risks in viral respiratory tract infections prevention and treatment, it acknowledges limitations and uncertainties in available evidence and calls for further research to clarify optimal use.
Johnston, C. S., Barkyoumb, G. M., & Schumacher, S. S. (2014, July 9). Healthy, nonsmoking men (n = 43; 18–35 years; BMI < 34 kg/m2) who did not engage in exercise training for competitive sports or use prescription medications were recruited from a large college campus in the Southwestern United States.Randomized Control TrialCold outcomes in participants ingesting 1000 mg vitamin C versus placebo daily for eight weeks *.These data demonstrate a measurable benefit of vitamin C supplementation for reducing cold episodes in young men with low to average vitamin C status. In addition, the data suggest a modest benefit of vitamin C supplementation for enhancing weekly activity levels in young men. The study was limited to its small sample size. Study started with 43 individuals However, it appears that due to various reasons (non-compliance, severe cold reported during the trial), the final analysis included 28 participants
-Only included men with low-to-adequate vitamin C status; hence, generalizability of these results can only be extended to similar populations and seasons.

Clinical Bottom Line:

Please include an assessment of the worth to practice

We conclude that routine use of Vitamin C supplements does not have any effect at preventing the common cold. However, at higher doses (2 G or more) it may provide some benefit at preventing and decreasing the duration of the common cold. We conclude that common cold prophylaxis using Zinc is not strongly supported by literature. However, it may help in reducing the duration of symptoms by 2 days.