Small Intestinal Bacterial Overgrowth, (brief overview for doctors)

 Small Intestinal Bacterial Overgrowth (SIBO)

Definition: This condition is defined by excessive amount of bacteria in the small intestine, esp. the type of bacteria normally found in the colon.  The small intestine is supposed to be relatively free of bacteria to allow for maximal absorption of nutrient from the food.

Symptoms: Gas, bloating, abdominal pain, nausea, diarrhea, constipation, flatulence.

There are a number of factors that normally keep the small intestine relatively free of bacteria, including the following:

  1. Hydrochloric acid secretion from the stomach
  2. Pancreatic enzymes
  3. Bile secreted from the gall bladder
  4. Gastrointestinal motility
  5. An intact illeocecal valve, which prevents colonic bacteria from migrating into the small intestine.

SIBO is increasingly being recognized as the cause of IBS, which previously was thought to be a psychosomatic condition, for which antidepressants were prescribed.

DIAGNOSIS:  Typically through breath testing, which involves a patient ingesting either glucose of lactulose and then measuring hydrogen and methane levels in the breath every 30 minutes for two hours.   The gold standard is taking a culture from a sample taken from the small intestine. But this is invasive, expensive, and problematic, since it will not be positive if the sample does not come from the portion of the intestine where the bacteria is growing. For these reasons, the breath test makes the most sense.

  • SIBO with increased hydrogen le vels is associated with IBS with diarrhea.
  • SIBO with increase methane is strongly associated with IBS with constipation.

If methane is present, it is not produced by bacteria but by even more primitive microorganisms known as Archaea, aka methanogens. Archaea lack a nucleus and defined organelles and are prokaryotes.  The process the hydrogen gas produced by the bacteria and give off methane.


  • Decreased hydrochloric acid, such as with chronic use of proton pump inhibitors (Prilosec)
  • Decreased pancreatic enzymes
  • Decreased bile
  • Decreased intestinal motility
  • Weakened immune system
  • Missing or malfunctioning illeocecal valve. Dr. Datis Kharrazian claims that the gas and bloating created by SIBO force this valve open increase SIBO. Can visceral manipulation have any benefit in these situations?
  • Common in diabetes (neuropathy leads to decreased motility), pancreatitis, loss of gall bladder, hypothyroid, intestinal obstruction, diverticulosis of small intestine, HIV, cirrhosis, hepatitis, sceroderma, and Fibromylagia (100% correlation in one study by Dr. Mark Pimentel) Note: Dr. Pimentel at Cedar’s is one of the leading experts on SIBO and has published a lot of research on it.
  • Pimentel feels that food poisoning is often the cause of SIBO. Toxins relased by the bacteria lead to neuropathy that causes decreased motility that causes SIBO.

SIBO leads to decreased absorption of nutrients from food, esp. vitamins A, D, E, B, fat and protein malabsorption.


  1. Rifaximin (a nonabsorbable antibiotic) or Rifaximin plus Neomycin (for SIBO with methane)
  2. Botanical protocals with natural antimicrobial products like Canidbactin AR and Candibactin BR from Metagenics, which have been shown in Dr. Mullen’s paper to be as effective as Rifaximin.
  3. Low FODMAP diet or the Specific Carbohydrate Diet. But Dr. Pimentel recommends not using the low FIODMAP diet while giving antibiotics, because it will starve the bacteria and they are harder to kill when the bacteria are in survival mode and form spores, etc..
  4. Increase intestinal motility. Dr. Kharrazian recommends exercises to increase motility, including gargling, purposely inducing a gag reflex, and coffee enemas. There are also prokinetic (motility increasing) drugs.
  5. No matter how it’s treated, SIBO tends to recur 40-60% of the time and requires multiple treatments.

Please note: this is written in summary form as an overview of this condition and was intended for integrative practitioners and doctors to read and is not intended for lay persons. Most of the other posts on my blog are intended for patients (lay persons) to read.

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