HIV and GI Issues: Small Intestinal Bacterial Overgrowth (SIBO)

A good balance of gut bacteria is important for overall health. Having too much bacteria in the wrong place can lead to health problems. Small intestinal bacterial overgrowth (SIBO) occurs when there are too many bacteria in the small intestine. The small intestine is the part of your digestive (gastrointestinal or GI) tract where your food gets broken down. This process allows your body to access the nutrients in food.^1,2

SIBO can cause problems like bloating, indigestion, and malnutrition. People with autoimmune disorders, weakened immune systems, and HIV are more likely to have SIBO. SIBO may cause worse inflammation in people living with HIV.^1,3,4

What is small intestinal bacterial overgrowth?

SIBO is a health condition. It occurs when a person has too many bacteria, or the wrong type of bacteria, in the small intestine. SIBO can:^1,5

• Cause problems with digestion
• Disrupt the body's ability to absorb nutrients
• Lead to uncomfortable symptoms

What causes SIBO?

There are a few different factors that can lead to SIBO. They include:^1,5

1. Problems from abdominal surgery
2. Scar tissue or tissue sticking together (adhesions) in and near the small intestine
3. Medical conditions like Crohn's disease, scleroderma, celiac disease, and diabetes
4. Overuse of antibiotics, acid reducers, and narcotics

What are some symptoms of SIBO?

SIBO symptoms are similar to many other GI conditions. People living with HIV and chronic GI issues may have overlapping symptoms.^1,3,5

Symptoms of SIBO include:^1,5

• Pain or swelling in your abdomen
• Nausea
• Indigestion
• Diarrhea
• Constipation
• Gas
• Unintentional weight loss
• Fatigue
• Malnutrition
• Loss of appetite

The complex relationship between nerve problems, HIV, and SIBO

The relationship between HIV and SIBO is not fully understood. We do know having HIV is a risk factor that can contribute to SIBO.^1,3,5

Research shows there is a link between nerve problems in people living with HIV and the development of SIBO. Many living with HIV experience neuropathy or nerve dysfunction as a complication of having the virus. SIBO is common among people with HIV-related neuropathy.^4,6,7

Problems with the vagus nerve can cause the digestive tract to slow down, creating prime conditions for SIBO. This shift in bacteria can drive inflammation. Dysfunction of the vagus nerve, which helps control digestion, is also linked with SIBO.⁶

SIBO is connected with inflammation in people living with HIV. Having HIV, vagus nerve dysfunction, and SIBO may lead to more chronic and disruptive inflammation. This can be problematic as inflammation drives HIV progression.^4,6

Treatment options for SIBO

SIBO usually stems from another health condition. Treatment should address the underlying problem and combat overgrowth. Treatment should also help correct any nutritional deficiencies.^1,5

Antibiotics are the most common first step to treating SIBO. Diet changes and nutritional supplements may be recommended. There is limited evidence that the drug pyridostigmine can improve SIBO in people living with HIV. More research is needed.^1,4

Is there a link between SIBO and irritable bowel syndrome?

Digestive issues and GI disorders are common among people living with HIV. Irritable bowel syndrome (IBS) and SIBO are 2 separate, but intertwined, health conditions.⁸

IBS is a common disorder that affects the stomach and intestines. The exact cause is unknown, but SIBO may be a driving factor. Changes in the gut microbes can play a role. Up to 80 percent of people with IBS also have SIBO.^1,3,5,9

SIBO and IBS have many overlapping symptoms. These symptoms can include:³

• Abdominal pain or swelling
• Diarrhea
• Bloating
• Constipation
• Gas
• Indigestion

Reviewed by: HU Medical Review Board | Last reviewed: December 2022