Dieticians have maintained that fiber (typically from fruits and vegetables) is an essential part of our diet, and that a high-fiber diet has many health benefits, including lower risk for developing coronary heart disease, stroke, hypertension, diabetes, obesity, as well as lowering blood pressure and serum cholesterol levels (Health benefits of dietary fiber). Now evidence is coming in as to why that is the case: fiber (that resists digestion by the body’s digestive system) is readily eaten by bacteria in the gut — fiber feeds the gut’s microbiome. Keeping the microbiome in good shape is essential for the proper functioning of the gut.
Here are two media article discussing both studies (which were carried out with mice, but will apply to human systems too):
Fiber Is Good for You. Now Scientists May Know Why.
And here are the two original studies:
Bifidobacteria or Fiber Protects against Diet-Induced Microbiota-Mediated Colonic Mucus Deterioration