What are the Symptoms of SIBO vs IBS?

Symptoms of SIBO vs IBS

Do any of these sound familiar to you? Painful bloating. Irregular bowel movements (constipation, diarrhea, or both). Excessive gas. Fatigue. Reflux. Abdominal cramping. In other words, does your overall digestion generally just suck?

For many, these types of symptoms result in a diagnosis of Irritable Bowel Syndrome (IBS).

But now, more doctors are diagnosing patients with a similar condition, Small Intestinal Bacterial Overgrowth, otherwise known as SIBO. Some research suggests that over 80% of those with IBS actually have SIBO.

With so much confusion between the two and so many overlapping symptoms, many are asking, what is SIBO? And what are the symptoms of SIBO vs IBS? Are they the same condition or different?

What is IBS?

IBS is a condition that affects movement in the digestive tract. In some cases the intestines move things through too quickly, causing diarrhea, cramping and sometimes even malabsorption. In other cases things slow down too much, producing constipation, gas, and a whole lot of discomfort. Unfortunately, many alternate between both.

IBS often acts as a catch-all diagnosis when other more serious conditions, like Crohn’s or Ulcerative Colitis, have been ruled out. IBS diagnoses usually include IBS-diarrhea (IBS-D), IBS-constipation (IBS-C), or IBS-mixed (IBS-M)

Common IBS Symptoms

  • Diarrhea and/or constipation
  • Abdominal pain or cramping
  • Abdominal bloating throughout abdomen
  • Gas/flatulence
  • Reflux/GERD
  • Nausea
  • Poor energy
  • Low iron status, anemia
  • Vitamin B12 deficiency
  • Vitamin D deficiency

Thankfully, IBS doesn’t typically cause any damage to the intestines themselves, but it certainly causes a host of unpleasant symptoms. Treatment strategies vary but usually include dietary changes and sometimes medications to ease the symptoms.

The most popular and perhaps effective diet for managing IBS is the Low-FODMAP diet. This diet reduces the intake of fermentable carbohydrates to help improve overall digestion.

What we are learning, however, is that many of those who respond well to a low-FODMAP diet may actually have a bacterial imbalance in their system called SIBO. This overgrowth of unwanted bacteria, in the small intestine specifically, may be the main cause of their IBS symptoms.

But how do we know? What is SIBO and what are the symptoms of SIBO vs IBS that can help us figure this out?

What is SIBO?

Small intestinal bacterial overgrowth is a condition in which an overgrowth of “bad” bacteria occurs in the small intestine. Typically sufferers may have methane-dominant or hydrogen-dominant SIBO, depending on the type of overgrowth, but it is not uncommon that someone may have both.

And while it is estimated that about 10-15% of people in this country have IBS, roughly 80% of those cases are actually caused by SIBO. This statistic is fascinating. This means that MOST people who are diagnosed with IBS have SIBO.

Common Symptoms of SIBO

  • Diarrhea and/or constipation
  • Abdominal bloating, usually in upper abdomen
  • Abdominal pain or cramping
  • Gas/flatulence, sometimes feels “stuck” and painful
  • Reflux/GERD
  • Nausea
  • Poor energy
  • Low iron status, anemia
  • Vitamin B12 deficiency
  • Vitamin D deficiency

As you can see, when we start to look at the symptoms of SIBO vs IBS, they are actually almost identical! So how are we supposed to tell these two conditions apart?

How to Tell the Difference: Symptoms of SIBO vs IBS

While the symptoms of SIBO vs IBS are quite similar, there are a few clues we can use to figure out which is which.

Bloating: While both conditions have bloating associated, it is more common in people with SIBO, and the bloating tends to be in the upper abdomen as opposed to lower. Because the bacteria associated with SIBO are up in the small intestine, that extra gas and pressure are usually in that upper region.

Gas/flatulence: Again, both conditions are known for producing excess gas, but people with SIBO often complain that the gas feels “stuck.” In fact, many with SIBO will complain that the gas and bloating build up and worsen as the day progresses. Sleeping often helps the gas get “unstuck,” but the cycle starts over again the next day.

Reflux/Heartburn/GERD: Reflux does not always occur in either condition, however those with SIBO will often experience heartburn due to the pressure from gas in the small intestine. That pressure pushes up on the esophageal sphincter, allowing acid to move up the esophagus.

Diet: There can be dietary triggers in either condition, but those with SIBO will often notice that high-FODMAP foods make the symptoms much worse. FODMAP foods feed the unwanted bacteria, so by lowering the intake of high-FODMAP foods, SIBO sufferers often feel better.

Food sensitivities can also exist in either condition, however, the bacteria associated with SIBO often increase the likelihood of “leaky gut,” which allows some food particles to pass through the intestinal wall and sets the stage for food sensitivity reactions. Those with SIBO may experience non-digestive symptoms from this including joint pain, migraines, brain fog, and even weight changes.

Malabsorption: Digestion and absorption are often impaired in people with SIBO. First, the contents of the stomach may move through too quickly, limiting the time for complete digestion. Second, the overgrowth of bacteria can cause a decrease in the release of digestive enzymes, which further limits the absorption of certain nutrients. And third, those with significant bloating and discomfort from SIBO may just not want to eat.

Testing: To really figure this out, testing for SIBO is available. A simple breath test can help someone figure out if they have an overgrowth and even uncover which type, whether hydrogen-dominant, methane-dominant, or both. There is currently no diagnostic testing for IBS; it is diagnosed based on symptoms.

Symptoms of SIBO vs IBS, at a glance

Symptoms of SIBO vs IBS

The Main Takeaway: Symptoms of SIBO vs IBS are Very Similar

How does one know if they have symptoms of SIBO vs IBS?

It can be very tricky to distinguish, however upper abdominal bloating, persistent reflux, malabsorption, and other random symptoms like brain fog, fatigue, joint pain and migraines are all signs it may be more than just IBS.

It’s important to figure out the difference as treatment strategies vary. A good first step is to get tested. Many gastroenterologists, naturopaths and even dietitans can help you get the right test and interpret the results.

Diet interventions can also be extremely helpful and are a key part of the process. A low-FODMAP diet may be a great place to start, and many dietitians such as myself specialize in these diets and can walk you through the process. Additionally, food sensitivity testing may help calm the digestive tract and clear up many symptoms.

Final Thoughts

Clearly, SIBO is a critical consideration in cases of digestive complaints, especially for those with IBS. In fact, many IBS diagnoses are actually SIBO in disguise as the symptoms between the two often overlap. Hopefully SIBO knowledge will continue to spread, allowing millions of people in this country to get the appropriate treatment for a condition that is treatable but unfortunately not always recognized in the gastrointestinal community.

Not sure if your digestive issue might be SIBO? I would love to review your health history with you and see what we can uncover. The right dietary protocol can often have you feeling better within weeks, and  I have a great group of MDs and NDs I refer to if further testing and treatment seem warranted. Don’t let these issues fester and worsen over time. Get started now!


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Image courtesy of Ohmega1982 / FreeDigitalPhotos.net

Danielle VenHuizen

Registered Dietitian, Certified LEAP Therapist