Effects of Probiotics on Markers of Oxidative/Nitrosative Stress and Damage Associated with Inflammation in Non-Communicable Diseases: a Systematic Review and Meta-Analysis of Randomized Placebo-Controlled Trials

Inflammation and oxidative/nitrosative stress (O&NS) are serious complications in non-communicable diseases (NCDs), including endocrine & metabolic and neurodegenerative diseases. The beneficial probiotic microbes, such as Lactobacillus , Bifidobacterium and Streptococcus , can decrease O&NS and inflammation. We conducted this systematic review and meta-analysis of randomized controlled trials (RCTs) to elucidate the effects of probiotics on O&NS and inflammation in NCDs. A systematic search of PubMed, Scopus and EMBASE resulted in the inclusion of studies if they met the eligibility criteria. Methodological quality was assessed using the Cochrane Risk of Bias 2 tool. Data (combined effect size) were analyzed using Meta Essentials software. Fifteen studies/16 trials with a total of 837 participants were reviewed. There was high and moderate certainty of evidence (GRADE) for the effectiveness of probiotic intervention ( vs . placebo) in increasing (↑) glutathione (GSH) levels [SMD(SE) = 0.89 (0.51)/ p  < 0.05, 95%CI -0.23 to 2.1, I ²  = 92.77%] and total antioxidant capacity (TAC) [SMD(SE) = 0. 75 (0.22)/ p  < 0.01, 95%CI 0.28 to 1.23, I ²  = 87.50%] as well as decreased (↓) malondialdehyde (MDA) (SMD(SE) = 1.03 (0.31)/ p  < 0. 01, 95%CI 0.37 to 1.7, I ²  = 93.88%) and C-reactive protein (hsCRP) (SMD(SE) = 0.74 (0.36)/ p  < 0.05, 95%CI -0.07 to 1.55, I ²  = 94.32%). There was no effects on nitric oxide, 8-hydroxy-2′-deoxyguanosine, interleukin-6, and tumor necrosis factor-α. Subgroup analysis to reduce heterogeneity indicated probiotic effectiveness on strain number (one/↑GSH), age bracket (41–60 year./↓MDA or > 61 year./↓hsCRP) and NCD (nervous system/neurodegenerative diseases/↑GSH and ↓hsCRP or rheumatoid arthritis/polycystic ovary syndrome/↑TAC). An overall low risk of bias was observed. In conclusion, probiotics may have beneficial effects on markers of O&NS and inflammation in patients with NCDs.