Gastrointestinal issues can feel like a mystery—even for many doctors. My gastroenterologist once told me it could take another decade before her field fully understands conditions like Small Intestinal Bacterial Overgrowth (SIBO). While research continues, understanding SIBO today can help prevent discomfort and long-term digestive problems. In this article, we’ll explore what SIBO is, how it develops, how it’s diagnosed and treated, and practical ways to reduce the risk of recurrence.
What Is SIBO?
Small Intestinal Bacterial Overgrowth, or SIBO, occurs when bacteria that normally live in the large intestine multiply in the small intestine. This imbalance can cause bloating, gas, abdominal discomfort, and nutrient malabsorption.
It’s important to remember: bacteria themselves aren’t “bad.” They play a crucial role in digestion and overall health. SIBO becomes problematic when bacteria migrate to areas where they shouldn’t be or when their numbers grow out of control.
How Does SIBO Develop?
Several factors can contribute to bacterial overgrowth in the small intestine:
- Undigested food: Proteins, carbohydrates, or fats that aren’t fully digested can feed bacteria, especially proteins from animal sources like meat, eggs, and fish.
- Delayed gut motility: The Migrating Motor Complex (MMC) helps sweep leftover food from the small intestine into the colon every 90–120 minutes during fasting. Slower gut movement gives bacteria more time to overgrow.
- Structural or functional issues: Conditions such as strictures, adhesions, or inflammation can trap bacteria in the small intestine.
- Liver and digestive enzyme function: The liver processes ammonia, a byproduct of protein breakdown, into urea for excretion. If the liver isn’t functioning optimally, ammonia can accumulate, potentially disrupting gut balance.
In short, undigested nutrients, slowed gut movement, and digestive or liver dysfunction can create the perfect environment for SIBO.
How Is SIBO Detected?
Doctors usually diagnose SIBO using breath tests, which measure gases produced by gut bacteria:
- Hydrogen: Often linked to diarrhea and rapid intestinal transit.
- Methane: Associated with constipation; produced by methanogens, a type of microorganism.
- Hydrogen sulfide: Less commonly tested but can cause bloating and diarrhea.
During the test, patients drink a sugar solution, and their breath is analyzed over several hours. Elevated gas levels suggest bacterial overgrowth. While useful, breath tests aren’t perfect—they can sometimes give false positives or negatives, so results are considered alongside symptoms.
Common Treatments
Conventional Medicine
Doctors often use antibiotics to reduce bacterial overgrowth:
- Rifaximin: Typically for hydrogen-dominant SIBO.
- Neomycin: Sometimes combined with Rifaximin for methane-dominant SIBO.
- Metronidazole: Broad-spectrum antibiotic; may impact overall gut microbiome.
- Fluconazole: Occasionally used for fungal overgrowth (SIFO), a related condition.
Functional Medicine
Some practitioners prefer natural antimicrobials, including:
- Allicin
- Oil of oregano
- Caprylic acid
- Monolaurin
- Grapefruit seed extract
- Pomegranate husk
- Methane-targeted supplements like Atrantil
Regardless of approach, the goal isn’t just to reduce bacterial numbers—it’s to address the root causes of overgrowth, such as motility, liver function, and gut health, to prevent recurrence.
Reducing the Risk of Recurrence
Treating SIBO is about more than eliminating bacteria—it’s about creating conditions where overgrowth is less likely to return. Key strategies include:
- Supporting gut motility: Chronic constipation is a major contributor. Fasting, fiber, and gentle movement can help keep the small intestine clear.
- Optimizing liver health: A healthy liver efficiently processes ammonia and supports digestion. Managing conditions like fatty liver or inflammation can improve gut balance.
- Reducing inflammation: Chronic inflammation in the gut, urinary tract, or reproductive system can promote bacterial overgrowth. Addressing conditions like ulcerative colitis, histamine intolerance, or endometriosis can help.
- Diet considerations: A low-FODMAP diet can reduce fermentable carbohydrates that feed bacteria. Long-term strategies should be personalized with a healthcare professional.
Take-Home Message
SIBO is a complex condition influenced by digestion, motility, liver function, and intestinal balance. Simply eliminating bacterial overgrowth is rarely enough—addressing underlying causes is essential. By supporting proper gut motility, optimizing liver health, reducing inflammation, and making dietary adjustments, you can create an environment where SIBO is far less likely to return.