SIBO is an acronym that means “small intestine bacterial overgrowth”. In SIBO abnormally large numbers of bacteria (usually defined as at least 100,000 bacteria per ml of fluid) are present in the small intestine. The symptoms of SIBO are similar to irritable bowel syndrome; they include abdominal bloating or distension, gas, diarrhea, and abdominal pain. In advanced cases, there may be vitamin and mineral deficiencies and weight loss.

One possible cause of irritable bowel syndrome (IBS) is bacterial overgrowth in the small intestine. In research appearing in the Journal of the American Medical Association (2004; 292(7): 852-858) suggests as much. Bloating immediately following a meal is an indication of small intestine bacterial overgrowth.

Hydrogen excretion after ingesting lactulose (a sugar), is found in 84% of subjects suffering from IBS. It is an indirect method for finding bacterial overgrowth in the small intestine, but there is no good direct method available. The symptoms of 75% of patients with IBS improve when small intestine bacterial overgrowth is treated.

Research appearing in the American Journal of Gastroenterology (December 2000;95(12):3503-3506) studied patients with IBS. The researchers were able to alleviate symptoms in 50% of the patients by killing the bacteria in the small intestine.

The intestinal tract is an ecosystem, containing several pounds of bacteria. Those bacteria should be confined to the large intestine. Many species of bacteria are beneficial and protect the intestinal lining, remove chemical toxins, produce vitamins and keep harmful bacteria in check. Supplements, known as probiotics, are often taken to replenish normal and helpful bowel bacteria. Research appearing in the American Journal of Gastroenterology (2000; 95(5):1231-8) demonstrated that taking probiotic bacteria can reduce the symptoms of IBS.

These small studies indicate that bacteria are involved in IBS. Looking at the intestinal tract like an ecosystem may be able to help us find an effective approach in treating this problem.