SIBO: Symptoms, causes, treatment, and diet

Small intestinal bacterial overgrowth (SIBO) is more common than doctors previously thought. It is more likely to affect females, older adults, and people with digestive issues, such as irritable bowel syndrome (IBS).

In this article, we discuss the symptoms, risk factors, and complications of SIBO. We also cover the best diets to relieve symptoms.

Signs and symptoms

The signs and symptoms of SIBO are similar to those of other digestive disorders, such as IBS and lactose intolerance.

They can vary in severity from mild stomach discomfort to chronic diarrhea, weight loss, and a reduced ability to absorb nutrients from food (malabsorption).

SIBO directly affects the gut, causing uncomfortable digestive issues. The symptoms of SIBO include:

  • stomach pain
  • bloating
  • diarrhea
  • constipation
  • nausea
  • unintentional weight loss


This bacterial overgrowth can happen either when bacteria from one part of the digestive tract travel to the small intestine or when naturally occurring bacteria in the small intestine multiply too much.

People may experience SIBO as a result of the following factors:

  • the abnormally slow movement of the digestive system
  • low levels of stomach acid
  • physical abnormalities of the small intestine
  • a weakened immune system

People with certain medical conditions are more likely to have SIBO. Doctors consider SIBO a complication of the following conditions:

  • cirrhosis
  • Crohn’s disease
  • celiac disease
  • hypothyroidism
  • HIV
  • diabetes
  • IBS
  • scleroderma
  • fibromyalgia

Other risk factors for SIBO include:

  • older age
  • being female
  • long-term use of proton pump inhibitors (PPIs), which are medications that reduce stomach acid production
  • previous bowel surgery
  • having recently completed a course of antibiotics
  • drinking alcohol

A few dietary guidelines may help relieve SIBO symptoms.

Gut bacteria feed on carbohydrates. In general, the SIBO diet limits carbohydrate intake to prevent bacteria from growing. People may also benefit from a diet that is low in fermentable foods or FODMAPs.

FODMAPs are short-chain carbohydrates that are commonly present in dairy products, grains, and certain fruits and vegetables. Reducing the intake of these foods may relieve the symptoms of SIBO and help people identify the foods that trigger them.

FODMAP foods include:

  • oligosaccharides: wheat, legumes, onions, asparagus
  • disaccharides (lactose): milk, yogurt, butter, soft cheeses
  • monosaccharides (fructose and glucose): fruits, honey, foods with added sugars
  • polyols: fruits that contain pits (for example, cherries and peaches), apples, mushrooms, green beans

The elemental diet is another option for people with SIBO. It is a liquid-based diet that doctors use to treat severe digestive illnesses. This diet supplies nutrients in an easy-to-digest form, making it possible for the body to absorb most of them before the bacteria can feed on them.

Although the elemental diet seems promising, it is expensive, complicated, and not sustainable. People are not allowed solid food or any drinks other than water during the diet. It is vital to speak to a doctor before attempting this diet.

Different dietary changes work for different people depending on their symptoms and how they react to specific foods. People who have SIBO can work with a doctor or nutritionist to tailor their diet to manage their symptoms.


Abnormally large populations of bacteria in the small intestine can have negative effects on the entire body. Bacterial overgrowth can make it difficult for the body to absorb fats and carbohydrates from food. It can also lead to vitamin deficiencies and excess gas.

Other complications that a person with SIBO may experience include:

  • a leaky gut
  • malnutrition
  • dehydration
  • joint pain
  • constipation
  • hepatic encephalopathy, a decline in brain function due to severe liver disease


Many people report SIBO symptoms months after completing antibiotic therapy. Prevention is a vital component of SIBO management.

People usually develop SIBO as a result of an underlying medical condition or a physical defect in the small intestine. Addressing and controlling the root cause of SIBO will lower people’s risk of reoccurrence.

Dietary and lifestyle changes may also prevent SIBO from returning. Eating plenty of plant-based foods and avoiding overly processed and sugary foods will allow good bacteria to flourish and stop unhealthful bacteria from overgrowing. Regular exercise may also help regulate the body’s digestive functions.


Small intestinal bacterial overgrowth (SIBO) is a medical condition in which a person has an unusually large population of bacteria in their small intestine.

SIBO is a complication of other digestive conditions, such as IBS, Crohn’s disease, and celiac disease.

SIBO treatments aim to correct the balance of bacteria in the small intestines. Broad-spectrum antibiotics can treat SIBO, and some people will also need to make dietary changes to address nutritional deficiencies. If possible, treatment should address the underlying medical condition that caused SIBO too.

Doctors still do not fully understand SIBO. Current and future studies that explore the human gut microbiome and the results of dietary changes in the management of digestive disorders will have a profound effect on future SIBO treatments.

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