Could Bacterial Overgrowth Be Causing Your IBS Symptoms?

nutrition Jul 07, 2014

If you struggle with Irritable Bowel Syndrome (IBS), you’re not alone.

In fact, 10-15% of the US population has IBS. That’s more than the number of people in the US with Type 2 Diabetes, and we know how prevalent that is.

IBS can occur anywhere in the digestive tract from the mouth to the anus. Therefore, your symptoms can vary widely from reflux and heartburn to bloating, gas, constipation, and diarrhea.

The problem with a diagnosis of IBS is that it’s simply a diagnosis of exclusion. Your doctor has ruled out Crohn’s, colitis, and other digestive diseases, and now has no clue what is causing your issues.

Many gastrointestinal specialists are now finding that an infection, such as Small Intestine Bacterial Overgrowth (SIBO), is the underlying cause of IBS. The majority of the bacteria in our digestive tract resides in the colon (large intestine). In fact, our body is made up of more bacteria than living cells. We need this bacteria for a healthy digestive system and strong immune system.

However, in the case of SIBO, bacteria from the colon starts moving upward toward the small intestine. The small intestine should have some bacteria present, but it is a different type than the bacteria that resides in the colon. These bacteria migrating from the colon start to interfere with your normal digestion and absorption of food,and you begin to experience the uncomfortable symptoms of IBS.

Some common symptoms of SIBO include:

  • Excess gas, flatulence, belching
  • Abdominal bloating from gas
  • Abdominal pain and cramping
  • Constipation and/or diarrhea
  • Nausea or heartburn
  • Irritable bowel syndrome
  • Multiple food sensitivities
  • Leaky gut
  • Fatigue
  • Malabsorption symptoms (anemia or fatty stools)
  • Rosacea
  • Neurologic and muscular diseases

As Dr. Mark Pimentel, Director of the Gastrointestinal Motility Program at Cedars-Sinai Medical Center, states in his book, A New IBS Solution, “Our studies, as well as later studies conducted by other researchers, have demonstrated the fact that bacterial overgrowth is the primary factor in cases of IBS.”


It is possible to test for SIBO, and there is one test that is considered the gold standard for SIBO testing- the Hydrogen Breath Test.

A hydrogen breath test can actually be used to diagnose several conditions- SIBO, H. Pylori, and carbohydrate malabsorption. This test measures the hydrogen and methane gas produced by bacteria in the small intestine. These two gases are produced by bacteria, not by humans. Therefore, if these gases are detected at certain levels, there is likely an overgrowth of bacteria in the small intestine.

To take this test, patients will drink a sugar solution, either glucose or lactulose, after a 1 or 2 day prep diet. The gases are then measured over a 2-3 hour period and compared to baseline.

Both the glucose and lactulose tests have their benefits and downfalls, but the lactulose breath test is generally preferred among experts. The reason for this is that the lactulose breath test can diagnose bacterial overgrowth in the lower part of the small intestine, which is thought to be more common.


Once the diagnosis has been made, there are several treatment options. There are prescription antibiotics, such as Rifaximin, that has been used successfully to treat SIBO. There are also excellent herbal antibiotic protocols that have proven very successful as well if you wish to avoid pharmaceuticals.

In addition to treatment with herbs or antibiotics, incorporating a real food diet is absolutely necessary. You want to remove all of the food that feeds the bacteria, such as refined sugar, and high carbohydrate foods like grains. Incorporating a Paleo-style low fodmap diet can be very helpful in your SIBO treatment.

Know someone who might find this article helpful? Please forward this to them!

A New IBS Solution, Dr. Mark Pimentel
Dr. Allison Siebecker,


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