| Del Piano et al., (2010) | Italy | Evacuation disorder | L. plantarum B. animalis lactis | 5.0 ×109 | 80:110:110b | 30 days | Increase in number of weekly evacuations in probiotics group |
| Fateh et al., (2011) | Iran | FC (Rome III) | B. longum, B. breve, L. casei, L. rhamnosus, S. thermophilus, FOS | 1.0 × 108 | 31:29 | 4 weeks | Increase in stool frequency in men receiving probiotics |
| Favretto et al., (2013) | Brazil | FC (Rome III) | B. lactis Bi-07 | 1.0 × 108 | 15:15 | 30 days | Increase in stool frequency in women receiving probiotics |
| Mazlyn et al., (2013) | Malaysia | FC (Rome III) | L. casei Shirota | 3.0 ×1010 | 50:50 | 4 weeks | Probiotics did not alleviate constipation severity, stool frequency, and consistency. |
| Waitzberg et al., (2013) | Brazil | FC (Rome III) | B. lactis, L. paracasei, L. rhamnosus, L. acidophilus and FOS | < 109 | 49:50 | 30 days | Synbiotics improved stool frequency and consistency in constipated women. |
| Ojetti et al., (2014) | Italy | FC (Rome III) | L. reuteri DSM17938 | 1.0 × 108 | 20:20 | 4 weeks | Probiotics increased stool frequency. No difference in stool consistency. |
| Ding et al., (2016) | China | FC (Rome III) | B. longum, L. acidophilus, E. faecalis, soluble fiber (Pectin) | 3.0 × 107 | 48:45 | 12 weeks | Synbiotic exhibited increased stool Frequency and improved stool consistency and constipation-related symptoms. |
| Cudmore et al., (2017) | Ireland | FC (Rome III) | B. bifidum, L. rhamnosus, L. acidophilus, psyllium/inulin | 6.0 × 108 | 35:34 | 4 weeks | Synbiotics did not significantly improve stool frequency. |
| Ibarra et al., (2018) | France | FC (Rome III) | B. animalis HN019 | 1.0 × 109/1010 | 76:76:76c | 4 weeks | No difference in stool frequency and consistency between the probiotics and placebo groups. |
| Lim et al., (2018) | Malaysia | FC (Rome III) | B. lactis BB12, L. plantarum LP01, inulin-oligofructose | 1.0 × 1010 | 43:42 | 12 weeks | No difference in stool frequency and consistency between the probiotics and placebo groups. |
| Dimidi et al., (2019) | United Kingdom | FC (Rome III) | B. lactis | 1.5 × 1010 | 37:38 | 4 weeks | There were also no improvements in stool output, symptoms, or quality of life between probiotics and placebo groups. |
| Martoni et al., (2019) | Canada | FC (Rome III) | L. acidophilus, B. animalis lactis, B. longum, B. bifidum | 1.5 × 1010 | 48:46 | 4 weeks | No difference in stool frequency and consistency between the probiotics and placebo groups. |
| Botelho et al., (2020) | Brazil | FC (Rome IV) | L. acidophilus, L. casei, L. lactis, B. bifidum, B. lactis | 5.0 ×109 | 21:14 | 30 days | Probiotics improved constipation-related symptoms. |
| Madempudi et al., (2020) | India | FC (Rome III) | B. coagulans Unique IS2 | 2.0 × 1010 | 50:50 | 4 weeks | Probiotics improved stool frequency and consistency. |
| Kang et al., (2021) | South Korea | FC (Rome III) | B. coagulans SNZ1969 | 1.0 × 109 | 40:40 | 8 weeks | Probiotics improved stool frequency and colon transit time. |
| Wang et al., (2021) | China | FC (Rome III) | S. thermophilus, L. bulgaricus, B. animalis | 1.0 × 1010 | 23:21 | 4 weeks | Probiotics improved constipation-related symptoms. |
| Mitelmao et al., (2022) | Brazil | FC (Rome IV) | Multiple combination of Lactobacillus and Bifidobacterium | 8.0 × 109 | 51:51 | 30 days | Probiotics improved stool frequency and consistency. |
| Takeda et al., (2023) | Japan | FC (Rome IV) and elderly (> 65) | B. longum BB536 | 5.0 × 1010 | 39:41 | 4 weeks | Probiotics improved stool frequency in elderly patients. |
| Wang et al., (2022) | China | FC (Rome IV) | B. bifidum CCFM16 | 2.0 × 109 | 53:50 | 4 weeks | Probiotics improved stool consistency. |
| Lai et al., (2023) | China | FC (Rome IV) | B. animalis subsp. lactis HN019, L. rhamnosus HN0001 | | 50:50 | 4 weeks | Probiotics improved stool consistency and constipation-related symptoms, but did not increase stool frequency. |
| Ma et al., (2023) | China | FC (Rome IV) | L. plantarum P9 | 1.0 × 1011 | 78:85 | 4,6 weeks | Probiotics significantly improved stool frequency and symptoms. |
| Cheng et al., (2024) | China | FC (Rome IV) | B. animalis subsp. lactis HN019 | 7.0 ×109 | 112:117 | 8 weeks | No difference in stool frequency in probiotics and placebo groups. |
| Salo et al., (2024) | Spain | Constipation | B. animalis subsp. lactis BLa80 | 2.0 × 109 | 23:23 | 4,8 weeks | Probiotics improved stool frequency. |
| Jin et al., (2025) | South Korea | Constipation | Multiple combination of Lactobacillus and Bifidobacterium | 2.0 × 109 | 33:37 | 4,8 weeks | Probiotics significantly improved stool frequency, consistency and symptoms. |
| Roos et al., (2025) | Sweden | Constipation | L. gasseri | 1.0 × 109 | 20:20 | 4 weeks | Probiotics improved constipation-related symptoms in women. |