Studies of cross-sections of people across the world suggest the more fiber you consume – especially if from a wide range of plant foods – the more diverse your gut microbiota will be. Additionally, intervention studies in people have shown that consuming more fiber and whole grains increases diversity of gut bacteria.

Different microbes are capable of breaking down (fermenting) different fibers. Holscher explains that it takes different enzymes to break down the various fibers found in foods. Some bacteria have many different enzymes, so they can utilize dozens of different fibers. Other bacteria may only be able to break down one or a few different fibers. By eating a variety of plant foods with different types of fibers, you may encourage the growth of a more diverse population of beneficial microbes capable of breaking down those fibers.