While dietary supplementation, nutrition and physical activity have been studied extensively for their respective roles in modulating the immune system response, specific strains of probiotics have also shown promise in the prevention of upper respiratory tract infection (URTI).
Supplementation with probiotics has been reported to reduce the incidence, severity and duration of gastrointestinal and respiratory illnesses. The beneficial effects are however dose and strain-specific. Evidence for the efficacy of probiotics surrounding respiratory illnesses has been shown in various sub-group populations including elderly, young, healthy, sedentary and highly trained athletes.
A randomised trial by West et al. (2013) found that daily supplementation of Bifidobacterium lactis BI-04 was associated with a statistically significant reduction in the risk of an URTI episode than to placebo supplementation.
Lactobacillus rhamnosus GG (LGG) is one of the most studied probiotic strains that helps to influence the immune response by stimulating antibody production as well as improving phagocytic activity of blood leukocytes. Data also has shown to support LGG treatment of abdominal pain-related functional gastrointestinal disorders and the prevention of diarrhoea in children. In this same meta-analysis (Liu, S., et al. 2013), LGG compared to placebo was also shown to be associated with a reduction in the incidence of URTIs.
A meta-analysis of 20 randomised controlled trials (RCTs) demonstrated that probiotics are capable of reducing the duration of illness of upper respiratory tract infection, and are associated with a statistically significant reduction sick days spent away from school, work and day care amongst those taking probiotics compared to placebo. The results of this review of a number of good quality RCTs suggests that probiotics can reduce duration of illness in otherwise healthy children and adults. It is important to note that different strains and doses of probiotics can have variable effects and some strains have more evidence than others.
Respiratory infections have also been reported to create dysbiosis in the gastrointestinal tract, for which probiotics have been extensively shown to play an important role in rebuilding the microflora.
King, S., Glanville, J., Sanders, M., Fitzgerald, A., & Varley, D. (2014). 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. The British Journal of Nutrition, 112(1), 41-54.
Laursen, R., & Hojsak, I. (2018). Probiotics for respiratory tract infections in children attending day care centres - a systematic review. European Journal of Pediatrics. 177, 979-994.
Liu, S., Hu. PW., Du, X., Z, T., & Pei, X. (2013). Lactobacillus rhamnosus GG Supplementation for Preventing Respiratory Infections in Children: A Meta-Analysis of Randomised, Placebo-controlled Trials. Indian Paediatrics, (50), 377-381.
Microorganisms - Effects of a Lactobacilli Probiotic on Reducing Duration of URTI and Fever, and Use of URTI-Associated Medicine: A Re-Analysis of a Randomised, Placebo-Controlled Study, source: https://www.mdpi.com/
West, N., Horn, P., Pyne, D., Gebski, V., Lahtinen, S., Fricker, P., & Cripps, A. (2013). Probiotic supplementation for respiratory and gastrointestinal illness symptoms in healthy physically active individuals. Clinical Nutrition Elsevier, 33(2014), 581-587.