What Is SIBO? Learn The Symptoms & Treatments For This Painful Gut Condition

mbg Associate Health Editor By Darcy McDonough, M.S.
mbg Associate Health Editor
Darcy is the associate health editor. She has a master’s degree in nutrition interventions, communication, and behavior change from the Tufts Friedman School of Nutrition Science and Policy.

Image by Cameron Whitman / Stocksy

It seems like lately everyone is popping probiotic supplements and munching on kimchi in the name of populating their gut with good bacteria. The more the bacteria the better, right? Not necessarily. It turns out it's not just the amount of good bacteria that matters but also the location of that bacteria. An overgrowth of bacteria in the small intestines, called SIBO, can actually cause painful bloating, constipation, and digestive issues. Don't go kicking your daily kombucha habit just yet, though—we are still all for probiotics, just as long as they are in the large intestines.

Here, learn everything you need to know about SIBO risk factors, symptoms, and treatment options.

What is SIBO?

SIBO is an acronym for small-intestinal bacterial overgrowth. SIBO is a condition in which there is too much bacteria living the small intestine, rather than the large intestine, where it belongs. Although what we call "the gut" stretches from the mouth to the anus, when people talk about gut health they are typically only referring to the large intestines. This is because the large intestines are where the majority of gut bacteria, also called microbiota, live. In fact, the colon is home to over 70 percent of all microbes in the human body. This huge collection of bacteria is integral to overall health, helping digest food, synthesizing vitamins, and bolstering the immune system.

All those good bacteria are only beneficial if they are in the right place, though—the large intestine and colon. When they travel back up into the small intestine, they can wreak havoc on the digestive system, causing bloating, discomfort, and diarrhea. Left untreated, SIBO can lead to malnutrition and has even been implicated in other digestive issues like IBS and "leaky gut."

What are the symptoms of SIBO?

  • Bloat
  • Diarrhea
  • Constipation
  • Weight loss
  • Abdominal cramps
  • Overfullness after eating
  • Gas
  • Irritable bowel syndrome (IBS)

The root of most SIBO symptoms is fermentation. Bacteria play a crucial role in digestion and absorption by feeding on undigested carbohydrates, sometimes called prebiotics, by the process of fermentation. This digestive process releases important by-products like vitamins and short-chain fatty acids, as well as gas. While the large intestine is wider and well-equipped for fermentation, the small intestine is much narrower. When there is an overgrowth of bacteria in the small intestine feeding on undigested food, the increased gas production can cause painful swelling and other issues.

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The SIBO-autoimmune connection you should know about.

You may have noticed, many of these symptoms overlap with other digestive issues like IBS. In fact, in some cases, IBS is simply misdiagnosed SIBO. The science is still emerging, but there is growing interest in how SIBO may influence and even trigger IBS and other autoimmune conditions.

"Because your gut controls 80 percent of your immune system and can regulate your mood and genetic expression, we're just beginning to see the far-reaching associations between SIBO and autoimmune conditions like autoimmune thyroiditis (Hashimoto's)skin conditions like rosacea, chronic conditions like diabetes, and seemingly unrelated conditions like fibromyalgia," Will Cole, D.C., IFMCP, functional nutrition expert, told mbg.

It is believed that the excess bacterial activity in the small intestine may cause inflammation and damage to the lining of the intestines, leading to "leaky gut syndrome." When you have a "leaky gut," toxins and undigested food particles can slip through the gut lining and into the bloodstream, causing inflammation throughout the body and potentially triggering autoimmune responses. However, this relationship is still being debated and researched.

Risk factors: What causes SIBO?

So, how does too much bacteria even end up in the small intestine, and who is at risk? Here are a couple of possible explanations:

1. Structural issues in the small intestine.

Structural damage to the small intestine is one of the main risk factors of SIBO. "During the night and in between meals, your gut normally has a function called the migrating motor complex (MMC), which pushes gut bacteria down into the large intestines," says Cole. "Typically, when there is decreased function of the MMC, the bacteria can grow up into the small intestines where it doesn't belong, leading to SIBO."

Infections, food poisoning, and some health conditions like celiac disease and diabetes can damage the intestinal structure and interfere with the MMC's ability to clear out excess bacteria. Abdominal surgery and scar tissue may also weaken the MMC. Diverticular conditions that cause small pockets to develop in the lining of the intestines are another common structural risk factor, especially in older adults.

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2. Medications

Certain medications may increase your risk of developing SIBO. In particular, proton pump inhibitors (PPIs) have been linked to SIBO. PPIs are commonly used to treat acid reflux and work by suppressing stomach acid. While excess stomach acid may be to blame for the painful symptoms of acid reflux, it is also crucial for keeping bacteria levels in check in the small intestines. When there are low levels of stomach acids, bacteria are free to flourish in the small intestines, leading to SIBO.

Antibiotics can also throw off the balance of bacteria in the body, leading to SIBO. The purpose of antibiotics is, of course, to kill off a bacterial infection. However, antibiotics also wipe out lots of good bacteria in the process. Regular and continuous use of antibiotics can skew the balance of bacteria and may cause SIBO.  

Diagnosis: How do you know if you have SIBO?

If you regularly feel bloated after meals, or experience abdominal pain, constipation, or diarrhea, you may want to check in with your doctor about SIBO. Unfortunately, SIBO can be hard to diagnose because its symptoms overlap with other common digestive issues and there are no standard diagnostic criteria. However, if you and your doctor suspect you have SIBO, expect to undergo a breath test.

As you know, the bacteria in your gut produce gases when they ferment fiber. The gas leaves your body in the form of well—passed gas but also when you exhale. Using a breath test, your doctor can detect what types of bacteria are in your gut as well as the approximate location of the bacteria.

When taking a breath test, first you will drink a sugar solution to encourage the carbohydrate breakdown in your gut and subsequent gas production. It should take about two hours for this carbohydrate solution to reach your large intestine and begin the fermentation process. However, if hydrogen is detected in the breath within 90 minutes of ingesting the sugar solution, it is likely that fermentation is happening farther upstream in the small intestines, which indicates SIBO.

It is important to note that this test is not perfect, and several other factors may influence transit time and gas production. For a more accurate diagnosis, you may need a more invasive procedure in which liquid is taken from the small intestines for testing.

Treatment: Can you treat SIBO with diet or medication?

Treatment for SIBO may vary depending on the underlying causes. For example, surgical intervention may be warranted if your doctor believes there is a structural issue in the intestines. In other cases, a targeted antibiotic may be prescribed to reduce and control the amount of bacteria present in the small intestines. In some cases, functional medicine practitioners recommend herbal antibiotics, including extracts from oregano, goldenseal, uva ursi, and garlic.

Diet is an important component of any SIBO treatment plan as well. Everyone's gut is different, so there is no single SIBO diet, but generally, a SIBO diet is similar to a low-FODMAP diet. FODMAP (an acronym that stands for Fermentable Oligo-, Di-, Monosaccharides And Polyols) are types of carbohydrates that can be difficult to digest, including lactose, grains, and sweeteners.

Diets low in FODMAPs have been shown to alleviate IBS symptoms that also plague SIBO suffers, like bloating, pain, and constipation. This is because eliminating FODMAPs can reduce the work your gut must put into digestion and limit the amount of gas produced. Additionally, bacteria feed off carbohydrates, so by limiting your consumption, you are cutting their fuel supply and discouraging proliferation. In some cases, Cole says he will also design a specific intermittent fasting protocol, where the patient limits food intake for a short period of time to starve out the bacterial overgrowth—but this doesn't work for everyone.

In many cases, eating the right diet in conjunction with taking conventional or herbal antibiotics can help clear up the bacterial overgrowth and get your gut back on track.

Ready to learn more about how to unlock the power of food to heal your body, prevent disease & achieve optimal health? Register now for our FREE web class with nutrition expert Kelly LeVeque.

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