Written by Dr. Michael Murray
Small intestinal bacterial overgrowth (SIBO) may seem like a new condition, but I first wrote about it over 35 years ago. At the time, in the early 1980s, there was a lot of focus on the overgrowth of Candida albicans in the intestinal tract as a factor in a complex set of symptoms. Yet, I noticed that many of the patients I was seeing had these symptoms, but no evidence of candida being out of control. Something else had to be responsible for their symptoms, and an overgrowth of bacteria in the small intestine seemed like a very good explanation. In the last 10 years or so, SIBO has pretty become a big buzz word in research and on the internet. Fortunately, there is a lot of good information.
The stomach and small intestine are designed to be relatively free of microorganisms. The reason should be obvious. The presence of microorganisms overgrowing in the small intestine would set up a scenario where they start utilizing various nutrients before they have had a chance to be absorbed. The result is fermentation of carbohydrates and putrefaction of proteins. This can produce a lot of gas as well as digestive symptoms that resemble the irritable bowel syndrome (IBS), along with some additional symptoms. IBS is associated with some combination of:
With SIBO, there are often other associated symptoms, including:
The primary way SIBO is diagnosed clinically is via breath testing. The test involves the patient ingesting a dose of either glucose or lactulose, then breathing into a collection bag every 20 minutes for measurement of hydrogen and methane. Normally these gases are not expired in high amounts, but with SIBO their levels can be quite high. Of the two sugars for testing, glucose usually gives more meaningful results, but only represents bacterial overgrowth in the first portion of the small intestine. Lactulose is more helpful if the overgrowth occurs in the ileum, the last part of the small intestine.
The diagnosis of SIBO via breath testing is given if the patient expired greater than normal levels of either hydrogen or methane. SIBO can be hydrogen dominant, methane dominant or mixed. Hydrogen dominant SIBO is most associated with diarrhea, while methane dominant is most associated with constipation. This difference reflects an overgrowth of different types of gut bacteria.
The small intestine is usually over 21 feet long and is divided into three segments: The duodenum is the first and 10 to 12 inches long, the jejunum is the middle portion and about eight feet long, and the ileum is last and about 12 feet long. The small intestine participates in all aspects of digestion, absorption and transportation of ingested materials. It secretes a variety of digestive and protective substances as well as receives the secretions of the pancreas, liver and gallbladder. Absorption of minerals occurs predominately in the duodenum, absorption of water soluble vitamins, carbohydrates, and protein occurs primarily in the jejunum, and the ileum absorbs fat-soluble vitamins, fat, cholesterol, and bile salts.
SIBO often represents a breakdown in protective mechanisms. There are several built-in factors that prevent bacterial overgrowth in the small intestine. Foremost are digestive secretions of bile and digestive enzymes along with the peristaltic contractions that move the food bolus through the small intestines. A lack of enzymes, bile or other digestive secretions, as well as reduced peristalsis, greatly increases an individual’s risk of having bacterial or candida overgrowth and an intestinal infection, including chronic candida infections of the gastrointestinal tract. Another key barrier to bacterial overgrowth in the small intestine is the ileocecal valve that separates the colon from the small intestine. Much like a door, this mechanical barrier is designed to prevent too many of the bacteria residing in the colon entering the small intestine.
The dietary approach to SIBO most often involves a low carbohydrate diet combined with strategies to deal with the bacterial overgrowth. A low FODMAP diet has emerged as the primary dietary strategy. FODMAPs are short-chain carbohydrates (oligosaccharides) and sugars that are fermented by intestinal bacteria, yielding large amount of gases, like hydrogen or carbon dioxide, thus causing abdominal bloating. Sources of FODMAPs include most legumes, vegetables, fruit and grains, so the diet is extremely limiting and not sustainable. Fortunately, recent studies indicate that the use of digestive enzyme supplements, especially those designed to digest the various offending oligosaccharides and sugars, may be as effective in improving digestive symptoms without having to forego so many health-promoting foods.
As far as dealing with the bacterial overgrowth, the conventional medical treatment of SIBO relies primarily on antibiotics. However, this approach ultimately creates additional problems due to further disturbance of the microbiome. In contrast, the natural approach focuses on dealing with the bacterial overgrowth by restoring the proper functioning of the protective barriers to SIBO or supplementation strategies designed to produce similar effects. To work toward this later goal, some use hydrochloric acid (HCl) replacement therapy, digestive enzymes and herbal agents that promote biliary secretions and peristalsis (e.g., berberine, ginger, artichoke, milk thistle and other choleretics). It is also helpful to use natural agents to reduce the bacterial overgrowth. Foremost among these agents, in my opinion, are digestive enzymes and berberine.
Digestive enzymes, especially proteases and lipases, are an important protective factor against SIBO. Insufficient output of digestive enzymes from the pancreas is associated with many symptoms associated with SIBO and may represent a key underlying factor in many cases. Digestive enzymes are also the likely host defense mechanisms within the gut that prevent the formation of biofilm, a collection of bacteria closely packed together that adhere to the lining of the small intestine within a slimy, gluey matrix. In general, methane-producing bacteria are more likely to produce biofilm and are often more difficult to clear.
Digestive enzymes are capable of eating away at the biofilm matrix, as well as acting as a deterrent for bacterial overgrowth in the small intestine. In general for SIBO, I recommend Digest Gold, a high potency digestive enzyme preparation, to be taken just before a meal. Digest Gold and other digestive enzyme preparations from Enzymedica use the Thera-blend technology. This exclusive process combines multiple strains of enzymes that work in various pH levels. Thera-blend enzymes have been shown to be three times stronger and work more than six times faster than other leading digestive supplements.
Berberine is an alkaloid found in many plants, including goldenseal (Hydrastis canadensis), barberry (Berberis vulgaris), Oregon grape (Berberis aquifolium) and goldthread (Coptis chinensis). Berberine can really help in SIBO. The advantage of it is that it exerts selective antimicrobial action against a wide range of disease causing organisms linked to SIBO, as well as against Candida albicans, yet exerts no action against health-promoting bacterial species like Lactobacilli and Bifidobacter species.
Several studies suggest berberine may be effective in SIBO. In animal models, berberine improves intestinal motility. This action is another key goal in patients with SIBO. While berberine has not been studied in SIBO, it has been studied in irritable bowel syndrome with very good results. In a 2015 double-blind study published in Phytotherapy Research, 196 patients with diarrhea-predominant IBS were randomized to receive either berberine (200 mg) or a placebo (vitamin C 200 mg) twice a day for eight weeks. The berberine group, but not the placebo group, reported significant improvement in diarrhea and less urgency and frequency in defecation. The berberine group also experienced a 64.6-percent reduction in abdominal pain compared with initial scores at the end of the study. Berberine significantly decreased the overall IBS symptom score, anxiety score and depression score. Lastly, and not surprisingly, berberine was associated with an increased quality of life score in patients, while no such change was seen in the placebo group.
Berberine has been extensively studied in clinical trials for supporting blood sugar and cholesterol levels, as well as blood pressure. I bring this up because in these studies the dosage was typically 500 mg two to three times daily before meals. This dosage level may bring about quicker results than those found in the eight-week trial in IBS and is more likely the dosage that would show more consistent results in SIBO.
Once symptoms suggest that the overgrowth of bacteria has been reduced, a repeat breath test or symptom evaluation will determine how successful treatment has been. If symptoms are 90-percent better, the next step will be prevention of recurrent SIBO by staying on the plan. If symptoms are still present after the appropriate time on antimicrobials, another breath test may be helpful to determine how much the levels have changed and whether continued treatment is necessary.
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