Small Intestinal Bacterial Overgrowth; What is it and how to treat

What is Small Intestinal Bacterial Overgrowth?

SIBO is a condition where too many bacteria grow in the small intestine.14,15 Normally, the small intestine contains relatively few bacteria compared to the large intestine or colon. The small intestine is where most digestion and absorption of nutrients takes place, so it's important to maintain the right balance of bacteria.

In SIBO, the microbiome of the gut is disrupted, allowing bacteria that normally live in the colon to overgrow in the small intestine.18,19

Certain groups may be at higher risk for SIBO. These include older adults, people with certain digestive disorders or autoimmune conditions, and those who have had abdominal surgeries or take certain medications that alter digestive function.20,21

When the bacteria in the small intestine get out of balance, it can cause digestive symptoms and complications. The excess bacteria interfere with normal digestion and absorption, causing gas, bloating, diarrhea, and even malnutrition in severe cases.14,15

Imagine your small intestine like a garden hose. Normally, water flows freely through the hose, just as food and nutrients flow through a healthy small intestine. But if the hose gets clogged with debris, the water can't flow properly. Similarly, when the small intestine is overgrown with bacteria, it can't function well to digest and absorb nutrients.

Symptoms and Causes of SIBO

The symptoms of SIBO can vary from person to person but often include:

• Abdominal bloating and distention
• Excess gas and belching
• Abdominal pain or discomfort
• Diarrhea or loose stools
• Constipation
• Nausea or queasiness
• Fatigue or weakness
• Unintended weight loss14,15

Many of these symptoms overlap with those of other digestive disorders like IBS, which can make SIBO challenging to diagnose. People with SIBO often feel uncomfortably full after eating, even small meals, and may feel like their food just sits in their stomach.

The bloating and distention can be so severe that people's clothes feel tight and they look visibly swollen. The excess gas can be uncomfortable. Some people with SIBO find they need to stay close to a bathroom due to frequent, urgent diarrhea.

With SIBO, bacteria can damage the intestinal lining and make it harder for your body to absorb important vitamins and minerals. This can cause deficiencies.5 This malabsorption and the frequent diarrhea can also cause dehydration and electrolyte imbalances.

There are several possible underlying causes of SIBO, including:

• Impaired motility: Conditions that affect the intestine's normal contractions and movement (peristalsis) can allow bacteria to stagnate and overgrow. These include diabetes, scleroderma, intestinal surgery, and opioid use.3,4
• Structural abnormalities: Physical issues like strictures, adhesions, diverticula, or a blind loop of intestine can create areas where bacteria can grow.3,4
• Decreased stomach acid: Stomach acid helps keep bacterial growth in check. Low stomach acid due to aging, autoimmune gastritis, or long-term use of acid-suppressing drugs can predispose to SIBO.2
• Immune dysfunction: The immune system helps control bacteria in the gut. Immunodeficiencies like IgA deficiency or HIV may increase SIBO risk.1
• Altered digestive secretions: Conditions affecting the pancreas, liver, or gallbladder can change the intestinal environment and bacterial growth.4

Often, it's a combination of factors that leads to SIBO. For example, someone may have low motility due to diabetes. Then they take an acid-suppressing drug and a round of antibiotics that disrupts their gut bacteria. This combination of factors allows the bacteria to get out of balance.

It's important to identify and address these underlying causes of SIBO. Otherwise, the overgrowth may come back after treatment.

Diagnosing and Treating SIBO

Because the symptoms of SIBO are similar to many other digestive disorders, it can be tricky to diagnose. If your doctor suspects SIBO based on your symptoms and risk factors, they will likely order a breath test.

The breath test measures the hydrogen and methane gas produced by bacteria in the intestines.18,19 You drink a sugar solution, and then your breath is collected at intervals to measure gas levels. High levels of hydrogen, methane, or both can indicate a bacterial overgrowth.

However, breath testing is not perfect.16,18 The test can be influenced by factors like recent antibiotic use or not properly following preparatory diet restrictions.

The best way to diagnose SIBO is a small bowel aspirate, where a sample of fluid is taken directly from the small intestine and checked for certain bacteria.12 However, this test typically isn’t the first test performed, as cost and convenience can be an issue.

Once SIBO is diagnosed, treatment typically involves a course of specific antibiotics to help reduce bacterial overgrowth.13 The most commonly used antibiotics are rifaximin, ciprofloxacin, and metronidazole. The choice and timeline of antibiotics depends on the specific case and breath test results.

Addressing underlying causes is a big part of SIBO treatment. This may involve strategies to improve gut motility, such as physical therapy, exercise, and prokinetic medications.4 It is also important to correct nutrient deficiencies, support digestive function, and restore a healthy gut microbiome.

Dietary changes are an important part of managing SIBO. Diets low in fermentable carbohydrates, like the low FODMAP or specific carbohydrate diet, can help starve the overgrown bacteria.17,22 Speak with your healthcare provider before starting a restrictive diet, as they can sometimes worsen nutrient deficiencies.

Probiotics may also be helpful for some people with SIBO. Specific strains like Saccharomyces boulardii and Lactobacillus plantarum have shown promise in reducing bacterial overgrowth and improving symptoms.11 However, probiotics are not one-size-fits-all, and in some cases can worsen SIBO. Work with a healthcare provider to help decide if probiotics are for you.

SIBO and Irritable Bowel Syndrome (IBS)

There is a significant overlap between SIBO and IBS. Studies estimate that 30-85%[a] of people with IBS also have SIBO, compared to only about 10% of people without IBS.9 This means that for many people with IBS, SIBO may be an underlying cause or contributing factor to their symptoms.

IBS is a functional gastrointestinal disorder that causes abdominal pain and changes in bowel habits. Like SIBO, it can cause bloating, gas, diarrhea, and constipation. IBS is divided into subtypes based on the main bowel symptom: IBS-D (diarrhea), IBS-C (constipation), or IBS-M (mixed).

SIBO is particularly common in the diarrhea-predominant type of IBS. One study found that over 50% of people with IBS-D tested positive for SIBO, compared to about 10% of those with IBS-C.10

The connection between SIBO and IBS is complex. On one hand, the gut decline and bacterial overgrowth of SIBO can directly cause IBS symptoms. The excess bacteria ferment carbohydrates in the intestine, causing gas, bloating, and irregular bowel movements.

On the other hand, the underlying causes of IBS, like gut motility disorders or intestinal inflammation, can also predispose you to SIBO. It's a bit of a "chicken or egg" scenario - which comes first, IBS or SIBO?

Regardless, SIBO can worsen IBS symptoms. One study found that IBS patients with SIBO had significantly higher rates of abdominal pain, bloating, and diarrhea compared to those without SIBO.10 This means that for many people with IBS, treating SIBO can lead to significant improvement in their symptoms.

SIBO is not the cause of everyone's IBS, however, and treating SIBO does not always resolve IBS completely. IBS is a complex, multifactorial condition that often needs a holistic, personalized approach to management.

Some people with IBS and SIBO may find that they need ongoing or periodic treatment to manage the bacterial overgrowth.

If you have IBS and haven't found relief with standard therapies, it's worth talking to your healthcare provider about testing for SIBO. Identifying and treating an underlying SIBO infection could help get your symptoms under control.

Managing SIBO and Maintaining Digestive Health

Treating SIBO is not a one-and-done process. Because SIBO often stems from an underlying cause, it’s common for it to come back. Up to half of people successfully treated for SIBO will have a recurrence within one year.6

This means that ongoing management and preventive strategies are important. This starts with identifying and addressing the root causes of SIBO, like motility disorders or nutrient deficiencies. Working with a gastroenterologist or functional medicine practitioner can help get to the bottom of why SIBO developed in the first place.

Dietary strategies can be helpful for managing SIBO in the long-term. Eating a diet rich in fiber, particularly from low-FODMAP sources like oats, carrots, and bell peppers, can help balance the gut microbiome and help bowel movements stay regular. Staying hydrated and limiting alcohol and caffeine can also support digestive health.

Some people find that intermittent fasting or time-specific eating patterns help manage their SIBO symptoms. By giving the digestive system regular breaks and reducing the constant intake of fermentable carbohydrates, these eating patterns may help control bacterial overgrowth. However, this approach isn't right for everyone, especially those at risk of nutrient deficiencies or disordered eating.

Stress management can also help with SIBO. The gut-brain connection is powerful, and psychological stress can have a significant impact on gut function. Stress-reducing practices like meditation, deep breathing, yoga, or tai chi can help support both digestive and overall health.

It's also important to be proactive about digestive health and stay alert for signs of SIBO recurrence. Symptoms like bloating, gas, diarrhea, and abdominal pain may mean it’s time to speak with your healthcare provider.

Maintaining overall digestive health is helpful for preventing SIBO recurrence. This includes staying hydrated, eating a balanced diet rich in fiber, managing stress, and engaging in regular physical activity.4 Avoiding excessive alcohol consumption and quitting smoking can also promote better gut health.

It's important to work with a healthcare provider to develop a personalized plan for managing SIBO and preventing recurrence. This may involve regular follow-up appointments, testing to monitor progress, and adjusting treatment as needed.

Conclusion

Small intestinal bacterial overgrowth is a complex condition that can cause a wide range of digestive symptoms and significantly impact your quality of life. It happens when there is too much bacteria in the small intestine, often because of underlying factors like gut motility issues, structural abnormalities, or certain medications.

Diagnosing SIBO can be difficult, as symptoms often overlap with other gastrointestinal disorders like irritable bowel syndrome (IBS). A few different tests may be run to confirm diagnosis.

Treatment for SIBO typically involves a course of antibiotics to reduce the bacterial overgrowth, along with addressing any underlying causes and managing symptoms through dietary changes and other supportive habits. Probiotics may also be helpful in some cases to restore a healthy gut microbiome.

There is a possible relationship between SIBO and IBS. Treating SIBO can lead to significant improvement in IBS symptoms if SIBO was an underlying factor for IBS.

Preventing SIBO recurrence involves managing underlying conditions, making dietary changes, and maintaining overall digestive health.

If you think you may have SIBO or are experiencing persistent digestive symptoms, it's important to speak with your healthcare provider. They can help determine the underlying cause of your symptoms, recommend appropriate testing, and develop a personalized treatment plan to help you manage your condition.

Citations:

<1>Adike A, et al. Small intestinal bacterial overgrowth: Nutritional implications, diagnosis, and management.</1>

<2>Mayo Clinic. (2020). Small intestinal bacterial overgrowth (SIBO) - Symptoms & causes. Retrieved from https://www.mayoclinic.org/diseases-conditions/small-intestinal-bacterial-overgrowth/symptoms-causes/syc-20370168</2>

<3>Mayo Clinic. (n.d.). Small intestinal bacterial overgrowth (SIBO) - Symptoms & causes. Retrieved from https://www.mayoclinic.org/diseases-conditions/small-intestinal-bacterial-overgrowth/symptoms-causes/syc-20370168</3>

<4>Medical News Today. (2022). SIBO: Symptoms, Treatment, Diet, and More. Retrieved from https://www.medicalnewstoday.com/articles/324475</4>

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<10>Chuah, K. H., Hian, W. X., Lim, S. Z., Beh, K. H., & Mahadeva, S. (2022). Impact of small intestinal bacterial overgrowth on symptoms and quality of life in irritable bowel syndrome. Neurogastroenterology and Motility, 34(11), e14305. https://doi.org/10.1111/nmo.14305</10>

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<19>Malik, B. A., Xie, Y. Y., Wine, E., & Huynh, H. Q. (2011). Diagnosis and pharmacological management of small intestinal bacterial overgrowth in children with intestinal failure. Canadian Journal of Gastroenterology, 25(1), 41-45. https://doi.org/10.1155/2011/524671</19>

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