The effects of probiotics on gastrointestinal symptoms and microbiota in patients with celiac disease: a systematic review and meta-analysis on clinical trials.

Gluten-free diet (GFD) is the most effective method to manage celiac disease (CD). Many patients do not reach the complete symptom alleviation, even by strict GFD. Recent studies have reported inconsistent results regarding the beneficial benefits of taking probiotics. Therefore, we aimed to evaluate the effects of probiotics on gastrointestinal (GI) symptoms and the possible underlying causes in CD and celiac disease autoimmunity (CDA) patients. Databases, including PubMed, Scopus, Embase, Web of Science and Google Scholar, were searched for clinical trials published until July 2022 about assessing the effects of probiotics or synbiotics on CD or CDA patients. We collected data on GI symptoms, CD markers, inflammatory and immune responses, adverse events, and gut microbiota. A random effect meta-analysis was used to estimate the pooled standardized mean difference (SMD) and confidence interval (CI). We screened 7234 articles, of which 14 were included in the qualitative analysis and 5 in the quantitative analysis. Probiotics might alleviate GI symptoms, especially in the highly symptomatic patients, and improve immune response in CD and CDA patients. Results of the meta-analysis showed that probiotics increased the abundance of Bifidobacterium (SMD: 0.72, 95%CI (0.13, 1.30) and Lactobacillus (SMD: 0.49, 95%CI (0.18, 0.80) as compared with placebo. Probiotics did not increase the adverse events compared to the placebo. Probiotics might alleviate GI symptoms and immune response and improve dysbiosis in CD and CDA patients. However, high-quality clinical trials are needed to increase the level of evidence. Also, the most suitable combination of probiotics is yet to find.