Our two favorite bacterial species/strains to ferment to make our age-reversing, socially-uplifting yogurt, L. reuteri DSM 17938 and ATCC PTA 6475, may also pose advantage for those of you with irritable bowel syndrome with constipation, IBS-C, more precisely known as methanogenic small intestinal bacterial overgrowth, methanogenic SIBO.
Methane-producing Archaeal species, i.e., microbes that predate bacterial evolutionarily such as Methanobrevibacter smithii, consume hydrogen gas and carbon dioxide in the bowels to produce methane gas that slows intestinal propulsive activity—“peristalsis”—that pushes forward the digestive remains of a meal. Should methane-producing species (that may also pose health advantages, such as consumption of TMAO, a discussion for another day) overpopulate, methane excess develops, slowing intestinal transit, AKA constipation, IBS-C, or methanogenic SIBO.
Among the lines of evidence suggesting that L. reuteri helps suppress methanogen over-proliferation:
L. reuteri DSM 17938 compared to placebo reduced symptoms of gas, abdominal discomfort, pain and bloating, and reduced complaints of incomplete defecation, i.e., symptoms of irritable bowel syndrome with constipation (IBS-C) or methanogenic SIBO.
Four weeks of L. reuteri DSM 17938 200 million CFUs per day resulted in partial improvement in constipation/frequency of bowel movements.
Four weeks of L. reuteri DSM 17938 administration in 20 adults was associated with a significant decrease of methane production determined by lactulose breath test (from 20.8 ± 15 to 8.9 ± 8.6; p < 0.0001 CI 95%) and of AUC value (from 5101.5 ± 3571.13 to 2128.4 ± 2110.8; p < 0.0001 CI 95%). Total disappearance of methane production was observed in 11 patients.
L reuteri 6475 is a vigorous former of biofilms that permit long-term residence and the 55730 (native strain related to 17938) produces the greatest quantity of reuterin, the main bacteriocin of this species, two qualities that enhance antibacterial effects. (This likely provides advantage in suppressing the species of H2-SIBO, also.)
For this and other reasons, I am increasingly convinced that L. reuteri is a keystone species, i.e., a species (perhaps strains) whose presence is critical because it supports the proliferation of other healthy bacterial species, while also suppressing potential pathogens like the Enterobacteriaceae species of SIBO and perhaps Archaeal species. Just as ocean plankton make it possible for higher creatures like jellyfish and whales to survive by feeding on them–i.e., a keystone species function, so I believe L. reuteri likewise acts as a keystone species to other microbial species. And it is a species that 96% of Americans have lost.