Probiotics for preventing acute upper respiratory tract infections
Abstract
Background
Probiotics may improve a person's health by regulating their immune function. Some studies show that probiotic strains can prevent respiratory infections. However, no evidence of the benefits of probiotics for acute upper respiratory tract infections (URTIs) and related potential adverse effects has been published.
Objectives
To assess the effectiveness and safety of probiotics for preventing acute URTIs.
Search methods
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 2), which includes the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (Ovid) (1950 to May week 1, 2011), EMBASE (1974 to May 2011), Web of Science which includes Science Citation Index (from 1900 to May 2011) and Conference Proceedings Citation Index (from 1991 to May 2011), the Chinese Biomedical Literature Database, which includes the China Biological Medicine Database (from 1978 to May 2011), the Chinese Medicine Popular Science Literature Database (from 2000 to May 2011) and the Masters Degree Dissertation of Beijing Union Medical College Database (from 1981 to May 2011).
Selection criteria
Randomised controlled trials (RCTs) comparing probiotics with placebo to prevent acute URTIs.
Data collection and analysis
Two review authors independently assessed eligibility, quality of trials and extracted data.
Main results
We included 14 RCTs, although we could only extract available data to meta‐analyse in 10 trials which involved 3451 participants. We found that probiotics were better than placebo when measuring the number of participants experiencing episodes of acute URTI: at least one episode: odds ratio (OR) 0.58; 95% confidence interval (CI) 0.36 to 0.92; at least three episodes: OR 0.53; 95% CI 0.36 to 0.80; rate ratio of episodes of acute URTI: rate ratio 0.88; 95% CI 0.81 to 0.96; and reduced antibiotic prescription rates for acute URTIs: OR 0.67; 95% CI 0.45 to 0.98. Probiotics and placebo were similar when measuring the mean duration (MD) of an episode of acute URTI: MD ‐0.29; 95% CI ‐3.71 to 3.13 and adverse events: OR 0.92; 95% CI 0.37 to 2.28. Side effects of probiotics were minor and gastrointestinal symptoms were the most common. We found that some subgroups had a high level of heterogeneity when conducting pooled analyses.
Authors' conclusions
Probiotics were better than placebo in reducing the number of participants experiencing episodes of acute URTIs, the rate ratio of episodes of acute URTI and reducing antibiotic use. This indicates that probiotics may be more beneficial than placebo for preventing acute URTIs. However, the results have some limitations and there were no data for older people.
PICOs
Plain language summary
Probiotics (live micro‐organisms) to prevent upper respiratory tract infections (for example, the common cold)
Acute upper respiratory tract infections (URTIs) include the common cold, inflammation of the trachea and larynx with symptoms including fever, cough, pain and headaches. Most acute URTIs are caused by viral infections and usually resolve after three to seven days. To reduce the course of the infection and make the person feel more comfortable, paracetamol, ibuprofen or aspirin and maintaining fluid intake are often recommended to reduce fever and ease pain and headaches. Antibiotics are prescribed if the illness becomes chronic and complications develop. Some live micro‐organisms can confer a health benefit to the patient when administered in adequate amounts. Lactic acid bacteria and bifidobacteria are the most common types of probiotics. They are commonly consumed in fermented foods, such as yogurt and soy yogurt, or as dietary supplements.
We searched electronic databases and identified 14 randomised controlled trials, although we could only extract available data to pool from 10 trials which involved 3451 participants, including infants, children and adults aged around 40 years. The live micro‐organisms intervention was found to be better than placebo in reducing the number of participants experiencing episodes of acute URTI and the rate ratio (calculated to compare the rate of events occurring at any given point in time) of episodes of acute URTI but the results in our review showed some limitations (for example, a high level of heterogeneity, few studies in some subgroups and no data for older people). Limited information from only three of the trials showed that live micro‐organisms can reduce the prescription of antibiotics. Side effects of probiotics were minor and gastrointestinal symptoms were the most common.
The evidence is weak but our review shows a benefit in using probiotics to prevent acute URTIs.
