Is Probiotic and Synbiotic Supplementation Effective on Immune Cells? A Systematic Review and Meta-analysis of Clinical Trials

Effect of probiotics on various parameters of immune system including immune cells count levels has been demonstrated by clinical trials; however, as far as we know, no meta-analysis has been done. The aim of this systematic review and meta-analysis was to evaluate the effect of probiotic/synbiotic on immune cells in health and disease status. We searched PubMed, SCOPUS, and Web of Science. All clinical trials investigated the effects of oral intake of probiotic/synbiotic on the cellular count of white blood cell (WBC), T and B lymphocyte, monocyte, neutrophil, eosinophil, natural killer (NK) cell count and activity, CD4 and CD8 cell, CD4/CD8, T helper (Th)1 and 2, and Th1/Th2 with duration of more than 7 days with concurrent control were included. Analysis of 108 clinical trials indicated a small significant increase in WBC count, T cell percentage, NK cell count and activity, monocyte percentage. No significant effect of probiotic supplementation was seen on the other immune cells. In conclusion, only a small significant effect of probiotic/synbiotic was seen on some of the immunity markers.