In the present study, the safety, tolerance and impact of 1×109 cfu Bacillus clausii CSI08, 1×109 cfu Bacillus megaterium MIT411 and a probiotic cocktail containing Bacillus subtilis DE111®, Bacillus megaterium MIT411, Bacillus coagulans CGI314, and Bacillus clausii CSI08 with a total count of 2.0×109 cfu administered daily were assessed as compared with a maltodextrin containing placebo control. A total of 98 study participants received daily doses for 45 days, followed by a washout period of 2 weeks. A questionnaire to capture the incidence and duration of upper respiratory tract, urinary tract and/or gastrointestinal complaints and a diary to capture stool regularity and consistency was kept daily to record compliance throughout the 45 days. Faecal and blood samples were collected for microbiological and haematological analysis at the start and end of the treatment period. The probiotic cocktail significantly decreased the incidence of loose stools throughout the entire study. The recorded respiratory, urinary and gastrointestinal symptoms, defecation frequency and other stool consistency were not influenced. No clinically relevant changes in blood parameters, such as liver and kidney function and no serious adverse events appeared during and after administration. There were no changes in symptoms including sadness, irritability, energy, appetite, tension, stress, sleep, cardiovascular events, aches and pains, and dizziness as determined by a mood questionnaire administered to participants at baseline and at the end of the treatment period. Similarly, the measured inflammatory cytokines, antioxidant levels, cholesterol, triglycerides, free amino acids or minerals remained unaffected. There were no negative changes in alpha or beta diversity of the microbiota with any of the treatment groups. These promising data suggest that these treatments were safe and well tolerated, and further work with larger cohorts are justified to determine the efficacy of these potential probiotics in select demographic groups. Trial registration number with clinicaltrials.gov at NCT 04758845.