Lactobacillus and/or Bifidobacterium strains present in yoghurt or dietary supplements were associated with fewer days of illness with a URTI per person, shorter illness episodes, and fewer days absent from daycare, school or work than participants who had taken a placebo.
The new review, which was authored by scientists from the York Health Economics Consortium (UK) and Dairy and Food Culture Technologies (California), was funded by the Global Alliance for Probiotics (GAP).
“The core of nutrition science is to advise on the construction of a diet that helps maintain health and reduce risk of disease,” said the paper’s lead author, Dr Sarah King, affiliated with York Health Economics Consortium (YHEC). “This paper shows that with the addition of live lactobacilli and bifidobacteria to your diet, the duration of upper respiratory tract infections (e.g. colds) could be shortened.
“Combined with results from a 2011 meta-analysis published in the Cochrane Database of Systematic Reviews, which demonstrated that probiotics can reduce the incidence of URTIs, the implications of these findings are significant, and could translate into cost savings and quality of life improvements.”
The cost savings could be significant, with data from the US Centers for Disease Control and Prevention indicating that 22 million school days and 20 million workdays in adults are lost annually due to the common cold in the USA. In addition, the economic impact of colds in the US is estimated to be about $40 billion every year.
Probiotics are defined as "live microorganisms which when administered in adequate amounts confer a health benefit on the host".
Meta-analysis details
Dr King and her co-authors evaluated the effects of different strains of Lactobacillus and Bifidobacterium on the duration of acute respiratory infections in otherwise healthy children and adults. Twenty randomized controlled trials (RCT) were identified from various scientific databases, of which 12 were considered to have a low risk of bias.
Crunching the numbers revealed that probiotics were associated with significantly fewer numbers of days of illness per person, as well as shorter illness episodes by almost a day, and fewer numbers of days absent from day care/school/work, compared to placebo.
“However, there was significant statistical heterogeneity between the studies that reported on the duration of illness episodes and those that reported on absenteeism from day care/school/work, but not for studies that reported on the number of days of illness per person,” wrote the authors. “This unexplained heterogeneity means that the effect size (i.e. the difference in the duration of illness episodes between treated and untreated individuals) may differ between the population groups.”
Dr King and her co-authors called on more research and additional meta-analyses to elucidate any differences between population groups.
Source: British Journal of Nutrition
Published online ahead of print, doi: 10.1017/S0007114514000075
“Effectiveness of probiotics on the duration of illness in healthy children and adults who develop common acute respiratory infectious conditions: a systematic review and meta-analysis”
Authors: S. King, J. Glanville, M.E. Sanders, A. Fitzgerald, D. Varley