Functional Roles of B‐Vitamins in the Gut and Gut Microbiome

The gut microbiota produce hundreds of bioactive compounds, including B‐vitamins, which play significant physiological roles in hosts by supporting the fitness of symbiotic species and suppressing the growth of competitive species. B‐vitamins are also essential to the host and certain gut bacterium. Although dietary B‐vitamins are mainly absorbed from the small intestine, excess B‐vitamins unable to be absorbed in the small intestine are supplied to the distal gut. In addition, B‐vitamins are supplied from biosynthesis by distal gut microbiota. B‐vitamins in the distal colon may perform many important functions in the body. They act as 1) nutrients for a host and their microbiota, 2) regulators of immune cell activity, 3) mediators of drug efficacy, 4) supporters of survival, or the fitness of certain bacterium, 5) suppressors of colonization by pathogenic bacteria, and 6) modulators of colitis. Insights into basic biophysical principles, including the bioavailability of B‐vitamins and their derivatives in the distal gut are still not fully elucidated. Here, the function of single B‐vitamin in the distal gut including their roles in relation to bacteria are briefly reviewed. The prospect of extending analytical methods to better understand the role of B‐vitamins in the gut is also explored. B‐vitamins and their metabolic derivatives in the distal colon perform many important functions in the body. They act as 1) nutrients for a host and their microbiota, 2) regulators of immune cell activity and modulators of colitis, 3) mediators of drug efficacy, 4) supporters of survival, or the fitness of certain bacterium, and 5) suppressors of colonization by pathogenic bacteria.