Effect of Probiotics Supplementation on Cortisol Levels: A Systematic Review and Meta-Analysis

Area of Science:

• Microbiology and Immunology
• Gastroenterology
• Endocrinology

Background:

• Conflicting results exist regarding probiotic effects on cortisol levels across diverse populations.
• Previous analyses were limited by study numbers and did not explore variations by health status, region, or treatment specifics.
• There is a need to synthesize current evidence on how probiotics influence cortisol and identify factors modulating this relationship.

Purpose of the Study:

• To systematically review and meta-analyze randomized controlled trials (RCTs) investigating the impact of probiotic administration on cortisol levels.
• To explore potential variations in probiotic effects on cortisol based on health status, concomitant medications, probiotic strain type, therapy duration, and geographical region.

Main Methods:

• A comprehensive search of multiple databases (PubMed, Embase, Scopus, etc.) was conducted for relevant RCTs.
• Random-effects meta-analysis was employed to synthesize data from 46 RCTs involving 3516 participants.
• Bias was assessed using the Cochrane RoB 2 tool, and evidence certainty was evaluated with GRADE.

Main Results:

• Overall, probiotic supplementation significantly decreased cortisol levels compared to controls (SMD: -0.45, low certainty evidence).
• Cortisol reduction was observed in subgroups without concomitant medications (SMD: -0.30), with single probiotic strains (SMD: -0.33), in healthy populations (SMD: -0.30), and in studies from the Asia region (SMD: -0.83).
• High heterogeneity (I² > 88%) was noted across most analyses.

Conclusions:

• Current low-certainty evidence suggests probiotics may lower cortisol levels.
• The effects appear more pronounced in specific subgroups, including healthy individuals, those not on other medications, and when using single-strain probiotics.
• More targeted research is required to elucidate the precise mechanisms and identify key variables influencing probiotic efficacy on cortisol regulation.