The problem with this article are statements about value of "fermentable" fiber without giving any real info about the nature of such fiber. (Except it's not digested by gut enzymes, hence "leftovers" that colonic organisms may be able to "ferment".)<p>There are <i>many kinds</i> of dietary fiber, it's actually quite a complex subject. The basic classification of "soluble" and "insoluble" is not very informative. As the article says, there are a great number of different organisms that can inhabit the "biome", each species of bacteria, fungus, virus, etc. has its own preferred substrates, and produces its own particular set of fermentation products.<p>I believe the research on biome activity is complicated by the vast range of variation among the organisms as well as the sorting out the beneficial or harmful effects of their activity on the host. And of course, we must not forget hosts also show a range of characteristics and are dynamically variable too.<p>As the article hints, research shows biome effects on many body functions, such as immune system and metabolic function. However, pinning down specifically what substrates are important to which organisms producing helpful/harmful effects is a daunting mission.<p>It's going to take a great deal more study before we will begin to have any clear idea about exactly which of the million different forms of fiber is going to be good (or bad) for any given health issue.