The risk of key biases present within each study
| Author, year | Random sequence generation | Allocation concealment | Selective reporting | Other biases | Blinding of participants and personnel | Blinding of outcome assessment | Incomplete data outcome | Additional information |
| Rudzki et al (2019)20 | Low | Low | Unclear | Low | Low | Unclear | High | 19 lost to follow-up; information concerning these individuals not included in report |
| Majeed et al (2018)23 | Unclear | Unclear | Low | High | Unclear | Unclear | Low | Authors employed by manufacturer of the intervention—Sabinsa, USA. Sabinsa also funded the trial |
| Kazemi et al (2018)21 | Low | Low | Low | Low | Low | Unclear | High | Attrition bias present; however, all subjects accounted for and details of loss to follow-up well explained |
| Miyaoka et al (2018)24 | Unclear | High | Low | Unclear | High | High | Low | Random group allocation insufficiently detailed; open label design (no blinding). |
| Ghorbani et al (2018)25 | Low | Low | Low | Low | Low | Unclear | Low | Independent company employed for randomisation protocols, no loss to follow-up. Blinding of results unspecified |
| Bambling et al (2017)26 | N/A | N/A | Low | High | High | N/A | High | No randomisation or control group. Patients and investigators knew what intervention was. Patients lost to follow-up (accounted for). Potential conflict of interest—researchers work with companies that seed fund, produce and research probiotics |
| Akkasheh et al (2016)22 | Low | Unclear | Low | Unclear | Unclear | Unclear | Low | Randomisation of groups and allocation claimed to be done; claimed outcomes were blinded, though no explicit details provided (therefore unclear). Attrition bias, participants included in analysis with intention-to-treat approach. Conflict of interest not stated |