The Effect of Probiotic Supplementation on Gastro-intestinal Symptoms and Mood States in Unprofessional Bodybuilders: A Randomized, Double Blind, Placebo-Controlled Clinical Trial Study

Background Emerging evidence suggests that probiotics may alleviate Gastrointestinal (GI) disturbances and positively influence mood by modulating the gut-brain axis. However, there is limited research specifically examining the effects of probiotic supplementation on GI symptoms and mood in bodybuilders. This study aims to investigate the effect of probiotics on Gastrointestinal health and psychological well-being in this population. Method This study was conducted as a randomized, double-blind, placebo-controlled trial involving 36 unprofessional bodybuilders. Participants were randomly assigned to two groups to receive either 2 billion colony-forming units (CFU) of probiotic (n = 18) or a placebo (n = 18) for 12 weeks. The change in symptoms wase determined using the Gastrointestinal Symptom Rating Scale (GSRS) and the Brunel Mood Scale (BRUMS). Results After 12 weeks of probiotic supplementation, athletes experienced a significant reduction in overall GSRS )p = 0.005), reflux (p = 0.04), and abdominal pain (p = 0.007) scores and significantly improved vigor (p = 0.002), peace (p = 0.004), and happiness score (p < 0.001) compared to their baseline measurements. Between-group analysis also revealed a significant reduction in reflux (p = 0.01), abdominal pain (P = 0.01), and overall GSRS scores (P = 0.02). We observed a significant rise in vigor (p = 0.02), peace (p = 0.01), and happiness score (p < 0.001). Conclusion The results demonstrated that probiotic supplementation has the potential to improve Gastrointestinal symptoms and mood states in athletes. Further studies with adequate power should be performed. Trial registration: Iranian Registry of Clinical Trials IRCT20240424061562N1, Registration date: 2024–07–30, Trial Id: 77722.