It’s a curious place, the small gut.
It occupies round 24-feet of all the 30-foot lengthy gastrointestinal (GI) tract, but it’s the least explored, least investigated phase of the human GI system. It’s because it’s comparatively inaccessible to endoscopy from above that may not often attain a lot past the duodenum, leaving the 24-feet of jejunum and ileum untouched. Likewise, a colonoscope can attain the ascending colon however can’t navigate the ileum. This can be a main sensible problem. Think about somebody is hemorrhaging from the small gut, 8 ft down from the duodenum, 16 or so ft ft up the colon—how do you determine, then cauterize or in any other case cease the hemorrhage? This has been a perennial problem in medical apply.
It additionally implies that, as a result of we generally make judgements concerning the intestinal microbiome by analyzing stool, we’re making judgements based mostly on colonic contents, not small intestinal contents, for the reason that contents of the small gut need to move by way of the colon earlier than exiting the physique. A stool pattern is a mirrored image of the composition of the sigmoid colon and rectum, i.e., the previous few inches of colon, and fewer consultant of, say, the ascending colon. The colon due to this fact introduces substantial change to the fabric passing by way of, obscuring what occurs within the small gut.
But it’s the small gut that’s liable for about 90% of nutrient absorption and nearly all of the intestinal immune response. Illnesses akin to Crohn’s illness, celiac illness, malabsorption (steatorrhea), irritable bowel syndrome (IBS), and small intestinal bacterial overgrowth (SIBO) are small intestinal, not colon, processes. The small gut, not the colon, is due to this fact the middle of the GI microbiome universe. However the small gut stays essentially the most elusive, most shadowy, phase of the human GI tract.
So how do you receive a pattern of ileal fluid to evaluate its microbiome composition? As a sensible matter, you merely can’t. We’re due to this fact left with making oblique observations about small intestinal physiology and microbiome composition.
Among the many oblique methods to evaluate small intestinal physiology and microbiome embrace:
- Vitamin B12 absorption happens within the ileum, a processed that’s impaired when the Proteobacteria species of SIBO have proliferated. In different phrases, vitamin B12 deficiency can point out SIBO (in addition to impairment of the parietal cells of the abdomen that produce the intrinsic issue vital for B12 absorption).
- Fats malabsorption, e.g., seeing fats droplets in the bathroom with a bowel motion, happens when the species of SIBO intervene with the motion of pancreatic enzymes within the duodenum and jejunum.
- Intolerances to any prebiotic fiber or polysaccharide (e.g., inulin, legumes, fruit, and so forth.) inside the first 90 minutes of consumption means that unhealthy microbial species have ascended up the small bowel, i.e., SIBO. In different phrases, it usually takes an absolute minimal of 90 minutes after ingesting one thing for it to traverse all the 24-feet of small bowel earlier than it reaches the colon the place fermentation usually happens. If it happens inside the first 90 minutes after ingestion, fermenting micro organism have to be within the small gut.
- Meals intolerances—As a result of it requires a minimal of 90 minutes for something you ingest to succeed in the colon, a meals intolerance to, say, FODMAPS, histamine-containing meals, legumes, fruit, nighthshades, and so forth. that happens inside the first 90 minutes of consumption is indicative of dysbiosis within the small gut, i.e., SIBO.
- H2-breath testing, as with the AIRE machine, is a approach to map whether or not H2-producing microbes have colonized the small gut and ferment sugars or prebiotic fibers to H2 gasoline inside the first 90 minutes of ingestion, parallel to prebiotic fiber intolerances.
- Serum lipopolysaccharide (LPS)–This could function an index of intestinal permeability and endotoxemia. Sadly, it doesn’t determine the LPS of all small intestinal species and stays a analysis instrument, not but clinically accessible.
- Serum zonulin—First recognized as an index of elevated intestinal permeability attributable to publicity to the gliadin protein of wheat, it might additionally function a gauge of elevated intestinal permeability attributable to dysbiosis/SIBO. Nevertheless, there are some methodological particulars that have to be labored out earlier than it reliably displays this course of.
The problems distinctive to the small gut imply that the insights we draw from stool testing could also be largely incorrect or incomplete. Given present strategies, we will due to this fact solely piece collectively a glimpse into what’s going on within the small gut from oblique items of data. Till we have now higher strategies, we have to take data akin to H2 breath testing or the presence of meals intolerances severely as indicators of small intestinal dysbiosis.