Small Intestinal Bacterial Overgrowth (SIBO) occurs when there is an excessive amount of bacteria, particularly those usually found in the large intestine, present in the small intestine. Normally, the small intestine has a low bacterial count, primarily absorbing nutrients rather than fermenting food. This overgrowth disrupts that balance, leading to various digestive problems. SIBO can be a chronic or recurring condition, causing persistent discomfort and impacting overall well-being.
Understanding Why SIBO Can Persist
SIBO often persists or recurs because it is a symptom of an underlying issue rather than a standalone condition. One factor is impaired gut motility, particularly dysfunction of the migrating motor complex (MMC). The MMC acts as a “housekeeping wave” that sweeps undigested food and bacteria from the small intestine into the large intestine between meals. When this mechanism is compromised, food and waste move too slowly, allowing bacteria more time to multiply.
Structural abnormalities within the digestive tract also contribute to persistent SIBO. Conditions like adhesions from previous surgeries, diverticula (small pouches in the intestinal lining), or strictures can create areas where bacteria accumulate and flourish. Reduced stomach acid production, known as hypochlorhydria, can allow bacteria that would normally be destroyed by stomach acid to survive and enter the small intestine. Certain medications, such as proton pump inhibitors (PPIs) which suppress stomach acid, or narcotics that slow gut motility, can also increase SIBO risk by altering the gut environment.
Recognizing Symptoms of Persistent SIBO
Individuals experiencing long-term or recurring SIBO report a range of digestive symptoms. Chronic bloating and abdominal distension are common, resulting from excessive gas produced by bacteria fermenting carbohydrates in the small intestine. Abdominal pain, often described as cramping, can accompany this bloating due to the stretching of intestinal walls by gas.
Changes in bowel habits are common, including persistent diarrhea, chronic constipation, or alternating patterns of both. Beyond digestive discomfort, SIBO can lead to nutrient deficiencies because overgrown bacteria consume vitamins and interfere with the absorption of fats, proteins, and carbohydrates. This malabsorption can manifest as unexplained weight loss and fatigue, impacting quality of life.
Diagnosing and Managing Chronic SIBO
Diagnosing SIBO involves non-invasive breath tests, which measure hydrogen and methane gases produced by bacteria after a patient consumes a sugar solution like lactulose or glucose. A rise in these gases indicates bacterial overgrowth in the small intestine. While breath tests are common, small bowel aspirate culture, involving an endoscopic procedure to collect fluid from the small intestine for bacterial analysis, is considered an accurate method, though it is more invasive and less commonly performed.
Managing chronic SIBO requires a comprehensive strategy that goes beyond eliminating the bacterial overgrowth. Initial treatment involves antibiotics, such as rifaximin or neomycin, or herbal antimicrobials, to reduce the bacterial population. Addressing the underlying cause of SIBO is important to prevent recurrence, as up to two-thirds of patients may experience a relapse within several months if the issue is not managed. This multi-faceted approach may include dietary adjustments, like a low FODMAP diet, to reduce fermentable carbohydrates that feed bacteria. Supporting gut motility through lifestyle changes or prokinetic agents, repairing any damage to the gut lining, and restoring a balanced gut flora are also important components of long-term management.
Potential Complications of Unaddressed SIBO
If SIBO remains unaddressed, it can lead to several health complications. The persistent bacterial overgrowth interferes with normal digestion and absorption of nutrients, resulting in chronic malabsorption. This can lead to deficiencies in various vitamins, particularly fat-soluble vitamins (A, D, E, K) and vitamin B12.
Vitamin B12 deficiency can cause neurological problems and anemia, with potential for irreversible neurological damage. Poor calcium absorption due to SIBO can contribute to bone diseases like osteopenia and osteoporosis, increasing fracture risk. The chronic inflammation and damage to the gut lining caused by SIBO can also contribute to increased intestinal permeability, sometimes referred to as “leaky gut,” and may be linked to broader systemic health issues.