Liisa Lehtoranta, Markus Lehtinen, Arthur C. Ouwehand
The common cold and flu are very common human diseases affecting all age groups. There are no cures for the common cold which is caused by over 200 viruses, although vaccines against influenza viruses are available. The potential beneficial effects of probiotics for the common cold have been widely studied. Meta-analyses show that probiotics have general benefits, with some strains performing better than others. This review focuses on the effects of probiotics on the common cold and flu. We discuss the aetiology of and immune responses to cold viruses and the possible mechanisms of action of probiotics. In addition, we review specific clinical studies investigating probiotic efficacy in respiratory infections in children and adults. We also discuss whether probiotic consumption for reducing risk of colds and flu could result in cost savings for society.