Small Intestinal Bacterial Overgrowth (SIBO)

Small intestinal bacterial overgrowth, or SIBO, happens when too many bacteria grow in your small intestine. Your small intestine normally contains far fewer bacteria than your large intestine. When bacteria from the large intestine move upward or multiply too quickly, they can interfere with digestion and nutrient absorption.

These excess bacteria feed on the food you eat before your body can absorb it. This creates gas, inflammation, and damage to the intestinal lining. Over time, SIBO can lead to deficiencies in important vitamins and minerals. The condition affects an estimated 6 to 15 percent of healthy people and up to 80 percent of people with irritable bowel syndrome.

SIBO is not a lifelong sentence. With proper testing and treatment, most people see significant improvement. The key is identifying the root causes and addressing them through diet, lifestyle changes, and targeted therapies.

SIBO symptoms often overlap with other digestive conditions, which can make it tricky to identify. Common signs include:

• Bloating and abdominal distension, especially after meals
• Gas and flatulence
• Diarrhea or loose stools
• Constipation or alternating bowel habits
• Abdominal pain or cramping
• Nausea and loss of appetite
• Fatigue and weakness
• Brain fog and difficulty concentrating
• Unexplained weight loss
• Nutrient deficiencies, including low vitamin B12 and iron

Some people with SIBO have mild symptoms that come and go. Others experience severe digestive distress that affects daily life. Nutrient deficiencies may develop silently without obvious digestive symptoms at first.

SIBO develops when the normal mechanisms that control bacterial growth in the small intestine stop working properly. Low stomach acid allows more bacteria to survive the journey from your mouth to your intestines. Slow intestinal movement, often caused by conditions like diabetes or hypothyroidism, gives bacteria more time to multiply. Structural problems like diverticula or strictures create pockets where bacteria can accumulate. Previous abdominal surgery can also alter normal anatomy and motility.

Risk factors include prolonged use of proton pump inhibitors or acid-blocking medications, which reduce protective stomach acid. Chronic pancreatitis, celiac disease, Crohn's disease, and other inflammatory conditions increase risk. Immune system problems and chronic stress can also contribute. Aging naturally slows digestive motility, making older adults more susceptible to SIBO.

SIBO is typically diagnosed using a breath test that measures hydrogen and methane gases after you drink a sugar solution. Elevated gas levels indicate bacterial overgrowth. This test is usually performed at a gastroenterology clinic. Some practitioners also use small bowel aspirate and culture, which involves taking a fluid sample during an endoscopy, though this is more invasive.

Blood tests can reveal the consequences of SIBO, particularly nutrient deficiencies. Rite Aid offers testing for methylmalonic acid, which becomes elevated when vitamin B12 is low due to malabsorption from SIBO. Testing these markers helps identify whether bacterial overgrowth is affecting your nutritional status. Your results can guide treatment decisions and help monitor your progress over time.

• Antibiotics like rifaximin to reduce bacterial overgrowth
• Herbal antimicrobials as an alternative or complementary approach
• Low FODMAP diet to reduce fermentable foods that feed bacteria
• Specific carbohydrate diet or elemental diet in severe cases
• Prokinetic medications to improve intestinal motility
• Digestive enzymes to support nutrient breakdown and absorption
• Probiotics chosen carefully, as some may worsen symptoms
• Treating underlying conditions like hypothyroidism or diabetes
• Stress management through meditation, yoga, or therapy
• Working with a gastroenterologist or functional medicine practitioner