What Is SIBO? A Functional Medicine Expert Explains How to Know if You Have It

What Is SIBO?

Small intestinal bacterial overgrowth (SIBO) is a condition where there is an abnormal increase of bacteria in the small intestine. The small intestine usually has lower levels of bacteria compared to the colon. When bacteria overgrow, it can lead to symptoms like bloating, gas, abdominal pain, diarrhea, and malnutrition.

What Causes SIBO?

There are several factors that can increase the risk for developing SIBO:

Intestinal motility disorders – Conditions that affect the muscular contractions that move food through the GI tract can slow transit time and allow bacterial overgrowth.
Structural issues – Scarring from surgery, diverticula (small pouches), intestinal obstruction can change the intestine environment and favor bacterial overgrowth.
Medications – Antacids, opioids, and other medications can slow GI motility.

Signs and Symptoms

Common symptoms of SIBO include:

Bloating or distension
Excessive gas
Abdominal pain or cramps
Diarrhea
Constipation
Nutritional deficiencies

Diagnosing SIBO

SIBO can be challenging to diagnose. Your doctor may order:

Hydrogen breath test – You ingest a sugar solution and breathe into bags to measure hydrogen gas production.
Antibiotic trial – Improvements with a course of antibiotics suggests SIBO.
Endoscopy with aspiration and culture – A small intestine fluid sample is taken to measure bacteria.

Treating SIBO

Common SIBO treatments include:

Antibiotics – To kill off excess bacteria in the small intestine.
Prokinetic medications – To improve intestinal motility.
Diet changes – Low FODMAP, biphasic, or antimicrobial diets.

Addressing underlying causes and sticking to the treatment plan is key for resolution. Some cases can be challenging to resolve. Work closely with your practitioner for continued support.

The Migrating Motor Complex: The Gut’s Internal Cleaning Crew

To understand why SIBO persists, one must look at the Migrating Motor Complex (MMC). This is a series of electrical impulses that occur in the small intestine during the fasting state—typically between meals and while sleeping. The MMC acts like a housekeeper, sweeping undigested food, debris, and excess bacteria from the small intestine into the colon. When the MMC is impaired due to stress, autonomic nervous system dysregulation, or prior infections, these “cleaning cycles” fail to trigger. This leaves behind a stagnant environment where bacteria can thrive. Patients often find relief by implementing a strict 4-to-5-hour fasting window between meals, allowing the MMC to complete its cycles without interruption from grazing or snacking, which effectively resets the digestive rhythm.

The Role of the Ileocecal Valve in Bacterial Reflux

The ileocecal valve serves as the physical gateway between the small intestine and the large intestine. Its primary function is to prevent colonic bacteria from backflowing into the small intestine. When this valve becomes incompetent, chronically open, or physically obstructed, colonic bacteria migrate upward, colonizing the small intestine where they do not belong. Functional practitioners often look for signs of ileocecal valve dysfunction, such as pain in the lower right quadrant or symptoms that worsen after specific physical movements. Manual visceral manipulation, performed by trained physical therapists or chiropractors, can sometimes help restore proper valve function, acting as a crucial adjunct to antibiotic or herbal protocols.

Nutritional Deficiencies Beyond Malabsorption

Beyond simple caloric loss, SIBO creates specific, often overlooked nutritional gaps. Because bacteria in the small intestine consume nutrients before the host can absorb them, iron deficiency, B12 deficiency, and fat-soluble vitamin (A, D, E, and K) malabsorption are common. For instance, bacteria can deconjugate bile acids, which are essential for fat digestion. This leads to steatorrhea (fatty stools) and a deficiency in fat-soluble vitamins. Patients should consider a comprehensive micronutrient panel if symptoms persist despite treatment, as restoring these levels is essential for gut lining repair and long-term metabolic health.

Herbal Antimicrobial Protocols as a Viable Alternative

While pharmaceutical antibiotics like Rifaximin are the gold standard, many patients find success with botanical alternatives. Research has shown that specific herbal combinations—such as oregano oil, berberine, neem, and garlic extracts—can be as effective as antibiotics in reducing hydrogen and methane gas levels. The advantage of an herbal approach is the ability to rotate agents to prevent bacterial resistance and the lower risk of harming commensal flora in the large intestine. However, these protocols must be monitored by a professional to avoid “die-off” reactions (Herxheimer reactions), which occur when high amounts of endotoxins are released as bacteria are neutralized, causing temporary flu-like symptoms or increased bloating.

The Brain-Gut Axis and SIBO Persistence

The gut is often called the “second brain,” and the bidirectional communication between the central nervous system and the enteric nervous system is critical to SIBO management. Chronic stress elevates cortisol, which suppresses digestive enzyme production and slows down intestinal motility. For many patients, the “fight or flight” state induced by modern life prevents the parasympathetic nervous system—the “rest and digest” state—from taking over. Incorporating vagus nerve stimulation techniques, such as deep diaphragmatic breathing, cold exposure, or meditation before meals, can significantly improve the efficacy of SIBO treatments by shifting the body into a state conducive to proper digestion and motility.

Biofilm Disruption: The Invisible Barrier

Bacteria are resilient organisms that often protect themselves by creating a sticky, protective matrix known as a biofilm. This matrix makes them highly resistant to both antibiotics and the immune system. If a patient experiences recurring SIBO, it is often because the treatment is only killing the “free-floating” bacteria, while the protected colonies within the biofilm remain intact. Practitioners may introduce biofilm disruptors—such as N-acetylcysteine (NAC), bismuth, or specialized enzyme formulations—several days before starting a SIBO treatment. This strategy thins the protective layer, exposing the bacteria and making them susceptible to eradication, which significantly lowers the rate of relapse.

FAQ

What are the most common symptoms of SIBO?The most common symptoms of SIBO are bloating, abdominal pain, excessive gas, diarrhea, and constipation. Malabsorption issues can also occur leading to nutritional deficiencies over time.What causes SIBO? SIBO usually occurs when there is intestinal motility dysfunction, structural issues, or impairment of the ileocecal valve. Risk factors include hypothyroidism, diabetes mellitus, and the use of certain medications like proton pump inhibitors or opioids.What tests diagnose SIBO?The primary methods for diagnosing SIBO are a hydrogen breath test measuring gas production after ingesting a sugar solution, an antibiotic trial to assess symptom improvement, or an endoscopy with aspiration and culture of small intestine fluid.What is the best treatment for SIBO?The most common SIBO treatments are a course of antibiotics like rifaximin, prokinetic medications, and dietary changes such as following a low FODMAP diet. Identifying and addressing underlying causes of SIBO is also an important part of management.Can SIBO come back after antibiotic treatment? Yes, it is possible for SIBO to recur after a course of antibiotics. To help prevent relapse, it is important to take any prokinetic medications as prescribed to improve intestinal motility, adhere to dietary recommendations, and treat any underlying conditions contributing to bacterial overgrowth. Some cases can be difficult to fully resolve.