Small Intestinal Bacterial Overgrowth

Small intestinal bacterial overgrowth (SIBO) happens when overall bacterial population increases abnormally in the small intestine—especially types of bacteria not commonly found in that part of the digestive tract. Once they reside in the small intestine, they can cause numerous symptoms because they ferment foods like fibres and sugars, which would normally occur in the large intestine. The process of fermentation leads to hydrogen, methane, or hydrogen sulfide gasses released in the small intestine, which may be a cause of symptoms like swelling, pain, dyspepsia, decreased colon motility (constipation), or increased osmotic flow into the colon (diarrhea). Typically, hydrogenic and hydrogen-sulfide SIBO are correlated with loose stools/diarrhea, whereas methagenic SIBO is correlated with constipation.¹ SIBO may be the underlying dysfunction of many digestive concerns, especially in people diagnosed with irritable bowel syndrome (IBS), as it is hypothesized that between 7% and 78% of people with IBS suffer from SIBO and, therefore, it is no longer a psychiatric-induced disorder.²

What Are SIBO Symptoms?

SIBO symptoms can include abdominal bloating and/or discomfort/pain after meals; excessive burping and/or gas; nausea; heartburn/gastroesophageal reflux disease (GERD), sensation of fullness and slow digestion; chronic loose stools and/or constipation; alternating loose stools and constipation; urgent bowel movements; steatorrhea (excess fat in feces), halitosis (bad breath) and/or bad taste in the mouth; skin issues like acne, rosacea³, fatigue, weight loss, and iron and/or vitamin B12 deficiencies⁴; or any combination of the above. The bacteria use both iron and B12 for their own metabolism, which may induce a functional deficiency of bioavailable iron and B12 in the body.⁵ SIBO can be suspected in cases where there is no clear explanation of iron deficiency anemia>⁶ or megaloblastic anemia.⁷ SIBO may also be suspected if the low-FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet is helpful or if eating a high-fibre diet aggravates intestinal symptoms. SIBO can be presumed if it is difficult to pinpoint which foods are aggravating symptoms through dietary restriction and if probiotics taken alone seem to provoke symptoms rather than improve them. There are indeed some foods that do tend to aggravate intestinal symptoms when SIBO is present, and these are garlic, onions, apples, pears, apricots, mangos, peaches, plums, cauliflower, broccoli, asparagus, cabbage, beans, lentils, and legumes.

The Underlying Cause

What is unique to SIBO, compared to other gastrointestinal (GI) disorders, is the dysfunction of the nerve-intestinal motility symptom in the body called the migrating motor complex (MMC).⁸ The MMC, when properly functioning, moves digested food from the small intestine to the large intestine. There is a possible association with acute viral gastroenteritis and the onset of IBS symptoms like chronic diarrhea, chronic constipation, and GERD.^9,10,11 The acute infectious illness is one way which the MMC may weaken¹², and factors associated with decreased MMC are long-standing diabetes or connective tissue disorder. In a study following a waterborne viral gastroenteritis (GE) outbreak, it has been shown that norovirus GE leads to the development of postinfectious IBS in a substantial proportion of patients (13%) ¹³, thus potentially leading to SIBO. When there is a dysfunctional MMC, the food is slower to move out of the small intestine, so there is inefficient sweeping of bacteria out of the small intestines to the large intestine.

There can be other causes in the development of SIBO, and these include hypochlorhydria or chronic antacid medication use¹⁴, bile insufficiency,^15,16 traumatic brain injury¹⁷, intestinal strictures/adhesions¹⁸, ileocecal valve dysfunction¹⁹, bowel surgery, celiac disease, gastroparesis (due to diabetes), and inflammatory bowel disease²⁰, or any disorder which causes either accumulation of bacteria in the small intestine through inefficient sweeping or retrograde from the large intestine.

There is a myriad of conditions associated with SIBO: intestinal permeability²¹, nonalcoholic fatty liver disease (NAFLD),^22,23 interstitial cystitis²⁴, hypothyroidism²⁵, restless-legs syndrome²⁶, histamine intolerance²⁷, gall-bladder removal²⁸, autoimmune conditions, Crohn’s disease²⁹, ulcerative colitis³⁰, systemic sclerosis^31,32.   Research has shown that NAFLD is correlated with increased intestinal permeability as well as higher prevalence of SIBO³³. Furthermore, nonalcoholic steatohepatitis (NASH) is also found to be significantly correlated with SIBO.³⁴ These findings, however, suggest correlation and not causation, and may be closely interlinked.

If SIBO is suspected, the SIBO breath test is a popular, noninvasive method. While research is still determining what is the most sensitive test, substrates that are used for the test often provide false positive results, and individual variation in intestinal transit time may also create both false negatives or positives.³⁵ Compared to the gold standard of upper-gut aspirate, breath tests have high specificity but very low sensitivity.³⁶ However, with proper guidance, the breath test can be helpful. If positive, then appropriate administration of an eradication treatment is utilized based on the results. Once the overgrowth is treated, digestive and associated symptoms are likely to resolve, and the digestive tract can then be taken care of with a recovery protocol using lifestyle and nutrition modification as well as plants and nutraceuticals.

What Is the SIBO Breath Test, and What Can You Expect?

The SIBO breath test includes a prep diet the day before testing to limit the chances of certain foods interfering with test results. SIBO bacteria feed mostly on sugars and plant products, so, according to the SIBO Centre for Digestive Health, the only foods to eat during the prep diet are:³⁷

• Any meat, poultry, fish, or seafood that is not cured or brined
• Plain, steamed white rice
• Eggs
• Clear meat broth (made only from the meat; no bone, cartilage, or vegetables)
• Fats/oils (coconut/olive/vegetable oils, butter, or lard)
• Salt and pepper (no other herbs/spices)
• Weak black coffee and/or weak black tea (plain, no sweeteners or cream, no green or herbal teas)
• Plain water (no mineral water or water with additives)

It is also recommended to do an overnight fast, and then a baseline breath sample is collected. The day of the testing, a solution is taken (typically lactulose), and breath samples are collected over the next three hours to assess hydrogen and methane production from the small intestine bacteria present.³⁸ If there is a rise in gasses, then this would be considered a positive result. Hydrogen and methane are the two main gasses that the SIBO breath test can detect. Newer breath tests can also detect hydrogen-sulfide gasses.^39,40,41

What to Do Following a Positive Test

There are two phases of SIBO treatment, which include the antimicrobial or eradication phase and the recovery phase, which includes digestive healing and prevention of SIBO recurrence.

First Step: The Eradication Phase

Treatment is dependent on which gasses were considered in the unhealthy range and would include two to four weeks of one or more of antimicrobials, which may include antibiotics (neomycine or rifamaxin)^42,43,44,45  antimicrobial herbs (goldenseal, myrrh, thyme, garlic, oregano, berberine, uva ursi, and silver hydrosol),^46,47 or, if nonresponsive to those, agents which are biofilm disruptors (if this is new to you, biofilm disruptors remove the protective coating on the bacteria we want to eradicate!). Biofilm disruptor examples include bismuth subnitrate, DMPS and alpha-lipoic acid, N‑acetylcysteine, and black cumin seed oil.^48,49 Other considerations for a holistic success include agents that support the detoxification pathways of the liver, to quench things like free radicals. These include milk thistle, turmeric, dandelion, artichoke, alpha‑lipoic acid, Schizandra chinensis herb, and N‑acetylcysteine. In practice, as a naturopath, it appears that the combination of antibiotics such as rifaximin and an herbal antimicrobial, possibly due to the other effects of plant medicines, are the most helpful for SIBO eradication.

Lactobacillus casei probiotic, with antibiotic treatment, have been demonstrated in one small study to be more effective than antibiotics alone for symptoms’ alleviation.⁵⁰ Saccharomyces boulardii probiotics may also be considered in individuals with short-bowel syndrome,⁵¹ but was not found to be effective in patients with IBS.

Eradication typically takes two to four weeks of treatment; however, biofilm agents may be used beforehand. As an alternative to antimicrobials, the elemental diet—which is a combination of amino acids, specific sugars, fats, vitamins, and minerals—can be utilized for periods of 14 to 21 days. The elemental diet is the only science-based diet to date that is potentially effective in reversing SIBO.⁵² However, this diet includes no solid foods, making it extremely difficult—and potentially harmful in certain vulnerable populations.

Second Step: The Recovery Phase

A simple suggestion for SIBO, to prevent its recurrence, is to space meals 2½–3 hours apart. This is the ideal time for the MMC to be able to complete its full contraction and sweep any bacteria from the small to the large intestine. As well, during treatment, fermented foods like kimchi, sauerkraut, kombucha, yogurt, miso, etc. should all be avoided so not to further feed the overgrowth of even beneficial bacteria in the small intestine!

Other gut healing supplements, if necessary, include L‑glutamine, zinc carnosine, N‑acetylglucosamine, and omega‑3s. Prokinetics (a type of drugs which enhance gastrointestinal motility), like a pharmaceutical called prucalopride⁵³, or natural treatments like 5‑hydroxytryptophane (5‑HTP) or ginger may be suggested to strengthen the MMC. Other pharmaceutical prokinetics include low-dose erythromycin⁵⁴ and low dose naltrexone, which is especially beneficial in those with autoimmunity. It is also crucial to support in case of gastric hypochlorhydria (which lowers the antibacterial function of the stomach) and/or lower-esophageal dysfunction, which can be done utilizing betaine hydrochloride, herbal bitters like gentian, or D‑limonene (also a mild prokinetic). Specific treatment recommendations are best discussed with your health-care provider, naturopathic doctor, or family physician.

Conclusion

SIBO is an increasingly common cause of digestive issues and, as mentioned, it can exacerbate many associated symptoms and health problems. It is imperative to eradicate the overgrowth, heal the digestive tract, and prevent SIBO recurrence for optimal health.