The combined use of B vitamins and probiotics promotes B vitamin absorption and increases Akkermansia abundance.

B vitamins and probiotics are commonly used dietary supplements with well-documented health benefits. However, their potential interactions remain poorly understood. This study aims to explore the effects and underlying mechanisms of the combined use of B vitamins and probiotics by liquid chromatography-triple quadrupole mass spectrometry analysis, pharmacokinetic modeling, and 16S rRNA gene sequencing. By intragastric administration of seven B vitamins and three Lactobacillus strains to healthy rats ( n = 8 per group), we found that probiotics significantly promoted the absorption (by approximately 14.5% to 71.2%) of vitamins B1, B3, B5, and B12. By conducting in vitro experiments ( n = 3 per group) and a pseudo-germ-free rat model-based pharmacokinetic study ( n = 6 per group), we confirmed that probiotics primarily enhanced the B vitamin absorption through gut microbiota-mediated mechanisms, rather than by directly producing B vitamins. Furthermore, we evaluated the effects of B vitamins and probiotics on the colon and gut microbiota by treating the pseudo-germ-free rats with blank solution, B vitamins, probiotics, and B vitamins + probiotics ( n = 5 per group), respectively. Histopathological examination showed that the combination of B vitamins and probiotics synergistically alleviated the rat colon damage. High-throughput genetic sequencing also revealed the synergistic effect of B vitamins and probiotics in modulating the gut microbiota, particularly increasing the abundance of Verrucomicrobia and Akkermansia . In summary, the combined administration of B vitamins and probiotics may have a higher efficacy than using them alone.