L. reuteri and methanogenic SIBO

Let’s consider an issue that is important to about 10% of people with small intestinal bacterial overgrowth, SIBO. Recall that SIBO is far more common than previously suspected.

The majority of SIBO involves diarrhea and is characterized by overgrowth of Enterobacteriacea that release the inflammatory trigger, lipopolysaccharide, that can enter the human bloodstream, explaining why people with SIBO have body-wide inflammation expressed, for instance, as fibromyalgia or autoimmune inflammation. Diarrhea-dominant SIBO is typically detected with hydrogen, H2, breath testing because Enterobacteriaceae convert sugars and prebiotic fibers to hydrogen.

But a minority of people with SIBO have constipation instead, along with bloating, excessive gas, and other symptoms, and are overpopulated with organisms such as Methanobrevibacter smithii, Methanosphaera stadtmanae, and other Methanobacteriales that produces methane gas. This is detectable by including a methane breath test in addition to the more common H2 breath test. Putting aside the health aggravations they produce by overpopulating the human gut, methanogenic creatures are fascinating members of an extremely ancient group of organisms called Archaea, with origins that pre-date the evolution of bacteria. Methane-producing Archaea such as Methonobrevibacter are therefore more closely related to organisms from hot springs and salt lakes than they are to other species that populate the human bowel, extreme environments that are inhospitable to bacteria.

Diarrhea-dominant SIBO has therefore received the bulk of research attention, since it is by far the most common variety. It means that less attention has been devoted to methanogenic SIBO and we lack many insights, such as understanding why methanogenic SIBO develops in some people but not in others and how to best deal with it.

The relative lack of insight into how to deal with methanogenic SIBO (should we add antibiotics such as neomycin or metronidazole that have worked anecdotally? should we opt for rifaximin over our herbal antibiotic choices?) makes this study all the more interesting, especially to us in the Undoctored lifestyle in which we have been making thick, rich yogurt to cultivate Lactobacillus reuteri ATCC PTA 6475 and DSM 17938, the species we know cause a marked rise in hypothalamic oxytocin when ingested, as well as having unique probiotic benefits in the upper gastrointestinal tract.

A small retrospective Italian study suggested that L. reuteri, specifically the DSM 17938 strain, suppresses methanogen activity: Effect of Lactobacillus reuteri (DSM 17938) on methane production in patients affected by functional constipation: a retrospective study.  20 participants with abnormally high starting levels of methane by (lactulose) breath testing had methane levels cut by over 50%, with 11 of the 20 participants experiencing complete elimination, while the other 9 had lower, though still abnormal, methane breath levels. (Interestingly, there was no reduction in H2 release.) In addition, constipation improved with L. reuteri supplementation with a mean of 4.1 BMs per week pre- to 6.4 BMs per week—nearly one per day—post. Note that the dose of L. reuteri was, by our standards (likely trillions in our yogurt) low at 100 million CFUs twice a day.

If such results are possible with L. reuteri DSM 17938 in just 4 weeks, what might happen over more time? And, of course, maintaining a intake of L. reuteri also yields all the other spectacular benefits we’ve been discussing.

So our favorite probiotic species, L. reuteri, once again looks like it yields huge advantage in restoring normal bowel health and other effects, in this case suppression of either methane production and/or reduction in methanogenic archaea. And doesn’t it make better sense to address constipation through a bowel flora manipulation than doing what most primary care doctors and gastroenterologists advise, i.e., laxatives, stool softening agents, and now expensive prescription drugs?