Effects of multistrain probiotics on metabolic biomarkers, inflammation, and antioxidant system in patients with type 2 diabetes mellitus: a prospective controlled trial in Türkiye

BACKGROUND: Recent evidence suggests that the gut microbiota plays a crucial role in the development and progression type 2 diabetes mellitus (T2DM). This study aimed to investigate the effects of multi-strain probiotic supplementation on glucose and lipid metabolism, inflammation, and antioxidant system in patients with T2DM. METHODS: This prospective controlled clinical trial was conducted at Ege University Faculty of Medicine from July 2020 to June 2023. Participants aged 35-65 years diagnosed with T2DM were allocated sequentially according to order of presentation to either probiotic group (n = 39) or control group (n = 38). The intervention group received a multi-strain probiotic supplement containing Lactobacillus acidophilus, Lactobacillus rhamnosus, Bifidobacterium lactis and Lactobacillus paracasei, twice daily for 12 weeks, while the control group continued standard care. This study evaluated anthropometric measurements, eating attitudes, dietary frequency, quality of life, and physical activity. Biochemical analyses included glycemic control, lipid profiles, inflammation markers (high-sensitivity C-Reactive Protein, Ceruloplasmin), and oxidative stress markers (Malondialdehyde, Glutathione). RESULTS: Seventy-seven of the 80 participants completed the study (mean age 55.38 ± 6.40 years, 42.86% female). After 12 weeks a significant within-group decrease in fasting blood glucose (FBG), postprandial blood glucose (PPBG), HbA1c, LDL-C, Non-HDL-C and malondialdehyde in the probiotic group compared to the control group (p < 0.001, p = 0.003, p = 0.004, p = 0.044, p = 0.034, p = 0.001). No significant changes were observed in inflammatory markers or oxidative stress markers' levels. Anthropometric parameters remained unchanged in both groups. In a two-group comparison, three-month multi-strain probiotic supplementation statistically significantly improved only PPBG in patients with T2DM (p = 0.038). CONCLUSIONS: Three months of multi-strain probiotic supplementation led to a significant reduction in PPBG levels among patients with T2DM, while FBG, HbA1c, lipid profile parameters, and inflammatory and oxidative stress markers showed improvements that did not reach statistical significance. CLINICAL TRIAL REGISTRATION: ClinialTrials.gov registration number: NCT07330388. Registered on 23 December 2025. https://clinicaltrials.gov/search?term=NCT07330388.