I’m not sure why I considered this, but maybe humans would be healthier if we “cleaned out” our intestinal bacteria periodically. What I’m suggesting is a complete eradication of intestinal flora by ingestion of inordinate amounts of antibiotics, followed by rapid inoculation with smaller levels of appropriate bacteria. The process would need to be closely monitored, and certain amino acids may need to be supplemented until large levels of bacteria have been restored. I have no idea what this would accomplish (other than potentially displaying a welcome mat for invasive species), but the concept of a “full reset” seems to be recurrently beneficial in our world, for everything from computers to environmental systems. Perhaps the aging prokaryotes in our guts gain mutations or begin behaving less effectively over the years (despite short generation times)? As far as I know, no one has been crazy enough to try to “reset” his internal bacteria in this way – probably due to the very real risk of death. If all normal internal species have been documented, replacing them rapidly shouldn’t be difficult (I presume), and it may or may not provide more efficient physiological function.
Interesting links (that I haven’t completely read yet):