ibs and sibo

What’s the Difference Between IBS and SIBO?

Two common digestive conditions often seen together are IBS and SIBO. IBS stands for irritable bowel syndrome. SIBO stands for small intestinal bacterial overgrowth. According to some research studies, up to 78% of IBS cases are associated with SIBO.

While symptoms of IBS and SIBO overlap, there are some key differences. In this article, we’ll review the differences between the two.

ibs and sibo - block letters spelling ibs

About IBS

Irritable bowel syndrome (IBS) is a digestive condition. It affects the large intestine but sometimes the small intestine too. There are three types of IBS.

  1. Diarrhea-predominant (IBS-D)
  2. Constipation-predominant (IBS-C)
  3. Mixed IBS

The exact cause of IBS is still unknown, but there are a few key factors involved.

The muscle contractions of the intestinal wall are abnormal. They are stronger and last longer than normal contractions, leading to gas, bloating, and diarrhea. In the case of IBS-C, the intestinal contractions are weaker and slower than normal.

There are also impairments of the digestive tract’s nerves. This leaves a person with IBS more sensitive to abdominal discomfort.

The condition also affects the connection between brain signals and the gut. This contributes to the symptoms, particularly pain, constipation, and diarrhea.

Up to one-third of IBS cases are “post-infectious.” This means they develop after an infection such as the stomach flu.

A key feature of IBS is an altered gut flora. Small intestinal bacterial overgrowth (SIBO) or an infection may trigger this.

Finally, there is a strong emotional component, such as stress, that can cause an IBS flare-up. Ceratin foods, particularly high FODMAP foods can trigger or aggravate it. These foods include sugars called fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.

IBS Symptoms

The symptoms of IBS include:

  • Bloating
  • Abdominal discomfort
  • Diarrhea
  • Constipation
  • Low energy
  • Poor focus and concentration
  • Skin rashes

Diagnosing IBS

Rome criteria help diagnose IBS as well. They include abdominal pain that is present for at least one day per week in the last three months, defecation-related discomfort, and altered frequency and/or consistency or stools. A colonoscopy, abdominal ultrasound, and other tests help rule out other digestive conditions.

IBS Treatment

Treating IBS involves dietary changes such as a low FODMAP diet. Various laxatives or antidiarrheal medications can also help depending on the subtype. Supplements such as probiotics and peppermint oil can help IBS-D and IBS-C.

ibs and sibo - illustration of bacteria in the small intestine

About SIBO

Small intestinal bacterial overgrowth (SIBO) is the presence of excessive amounts of bacteria in the small bowel. This bacteria is naturally found in the large intestine.

The increase in bacteria, particularly gram-negative bacteria from both aerobic and anaerobic species, leads to the fermentation of carbohydrates. This leads to gas and other digestive symptoms of SIBO. Unlike IBS, which affects the large intestine, SIBO affects the small intestine.

Like IBS, SIBO has three different subtypes.

  1. Diarrhea-predominant (SIBO-D)
  2. Constipation-predominant (SIBO-C)
  3. Mixed SIBO

An overgrowth of hydrogen-producing bacteria causes SIBO-D. An overgrowth of methane-producing microbes called archaea leads to SIBO-C.

Impairments in the muscle and nerve function of the gut lead to IBS. With SIBO, it’s the overgrowth of bacteria and archaea that causes problems with the muscle and nerves in the intestines.

Unbalanced gut flora is a key feature in both IBS and SIBO. However, in SIBO there are numerous microbes that populate the small bowel that normally lives in the large intestine.

SIBO Symptoms

Symptoms of SIBO are similar to IBS. These symptoms include:

  • Bloating
  • Abdominal pain
  • Diarrhea
  • Constipation
  • Joint pain
  • Low energy
  • Brain fog
  • Skin rashes like eczema and rosacea

SIBO also causes multiple vitamin and mineral deficiencies. Fat malabsorption also occurs, which can cause pale, bulky, smelly stool. These deficiencies are more severe than in IBS since the small bowel absorbs nutrients.

A person with SIBO and/or IBS will often have multiple food sensitivities. These sensitivities include:

  • Gluten
  • Dairy
  • Soy
  • Corn
  • Histamine-rich foods (strawberries, smoked and processed meats, aged cheese, and fermented products)

Diagnosing SIBO

Healthcare professionals do not base a SIBO diagnosis on symptoms or Rome criteria. Instead, they rely on breath tests available at a doctor’s office or online.

SIBO is not only associated with IBS, but with other conditions too. These conditions include:

It can also occur after gastrointestinal surgeries. Certain medications may also increase the risk of developing SIBO.

SIBO Treatment

The most effective treatment for SIBO is dietary changes, like a low FODMAP diet or gut and psychology syndrome (GAPS) diet. The specific carbohydrate diet (SCD) can benefit both SIBO and IBS.

The elemental diet, which consists of a protein shake, easily digested fats, and micronutrients is highly effective. It shows an 84% success rate but is very restrictive. This is why it’s reserved for severe SIBO cases.

Antibiotics like rifaximin and neomycin can treat SIBO. Some choose herbal antibiotics like oregano oil, neem, berberine, and allicin. You can also include probiotics in various protocols. For SIBO-C, you can use laxatives as well.


As you can see, there are similarities, but also differences between IBS and SIBO. However, it is important to note that they often coexist, and treating SIBO often leads to improvement in IBS symptoms. Therefore it is important to get the right diagnosis to get treated effectively.