Why do clinical guidelines for probiotics differ?

Clinical guidelines are recommendations for healthcare providers regarding patients with specific conditions. These guidelines should be based on practice experience and the best available research evidence. However, guidelines developed by various health organisations worldwide often do not agree with each other. This is also true for the current guidelines for the clinical use of probiotics. This article aims to provide examples of conflicting clinical guidelines for probiotics, define reasons for this phenomenon, describe standard tools for improving their quality, and suggest ways to enhance the development and assessment of suitable clinical guidelines for the appropriate clinical use of probiotics in specific conditions.