SIBO (Small Intestinal Bacterial Overgrowth)

What is SIBO?

SIBO stands for “small intestinal bacterial overgrowth.” It’s normal and healthy to have bacteria living in your small intestine, but too many can cause problems with your digestion — especially if they’re the wrong kind. The wrong bacteria can overwhelm the beneficial bacteria that you need to be there, and they can upset your digestive system by feeding on products that aren’t meant for them.

Bacteria in your small intestine digest carbohydrates and convert them into gas and short-chain fatty acids. More bacteria can mean more gas and other byproducts. When more bacteria are present and feasting, you might notice you feel gassier than usual. The bacteria also consume proteins and vitamin B12 meant for your body, and bile salts that are supposed to be there to help you digest fats.

All of this leads to poor digestion of fats and poor absorption of nutrients, especially calcium and fat-soluble vitamins. The result is a variety of gastrointestinal symptoms in the short term, and malnutrition in the longer term. Over time, vitamin and mineral deficiencies can cause lasting damage to your bones and nervous system.

How do you know if you have SIBO?

SIBO symptoms can resemble a variety of other gastrointestinal conditions, and often another condition has contributed to SIBO. You may experience some or many of these, depending on the severity of your condition:

• Abdominal pain.
• Abdominal distension.
• Nausea.
• Bloating.
• Indigestion.
• Gas.
• Diarrhea.
• Constipation.
• Unintentional weight loss.
• Fatigue.

What does SIBO stool look like?

SIBO may cause fat malabsorption that causes your poop to be smelly or oily. SIBO poop may also float. You may notice other changes, like:

• Soft, loose and watery poop.
• Mucus in your poop.
• Thin and pencil-like poop.
• Hard and lumpy poop.

What causes SIBO?

Your body maintains the balance of flora in your gut through a complex network of chemical and mechanical functions. For SIBO to occur, one or more of these functions must not be working correctly. SIBO has a variety of causes. These include chemical functions like low stomach acid and certain medications, and mechanical functions like small intestine dysmotility and structural problems in your small intestine.

Low stomach acid

Low stomach acid (hypochlorhydria) reduces your body’s ability to moderate bacterial growth. Factors that may reduce your stomach acid levels include:

• H. pylori infection.
• Prolonged use of medications like antacids and proton pump inhibitors (PPIs).
• Gastric bypass surgery.

Certain medications

Overuse of certain medications can upset the normal balance of flora. These include:

• Antibiotics.
• Narcotics.
• Gastric acid suppressants.

Small intestine dysmotility

Your small intestine normally has motility, or the ability to keep digestive contents moving. Small intestine dysmotility means that waste is retained for too long in your small intestine before emptying into your large intestine. This allows the small intestine bacteria to continue to multiply, while the large intestine bacteria may make their way into your small intestine. Some dysmotility disorders include:

• Gastroparesis.
• Intestinal pseudo-obstruction.
• Hypothyroidism.

Structural problems in your small intestine

Structural problems in your small intestine can inhibit motility and the regular clearing of residual bacteria and create extra nooks and crannies for bacteria to build up. Gastrointestinal diseases or complications of surgery can cause structural problems like:

• Small bowel diverticulosis.
• Small bowel obstructions.
• Abdominal adhesions.

What are the risk factors for SIBO?

As you get older, you gain more risk factors for SIBO. These include lower stomach acid and motility levels as well as higher levels of medications that might encourage SIBO.

Medical interventions like abdominal surgery and radiation exposure can cause structural problems in your small intestine as well as damage your mucosal lining, which affects your immunity.

Immunodeficiency disorders can affect your intestinal immunity to certain bacteria.

Certain gastrointestinal conditions can affect intestinal motility or create intestinal structural problems, including:

• Diabetes.
• Lupus.
• Celiac disease.
• Inflammatory bowel diseases.
• Irritable bowel syndrome.
• Pancreatitis.
• Colon cancer.
• Scleroderma.
• Chronic renal failure.
• Cirrhosis of the liver.

What foods trigger SIBO?

While foods aren’t the original cause of SIBO, certain foods do encourage the overgrowth of the wrong bacteria in your small intestine. If you’re feeding them their favorite foods, they’re going to grow more, and that will trigger more of your SIBO symptoms.

By the same token, you can help reduce the overgrowth by starving the problematic bacteria of their favorite foods. This strategy has led to a number of proposed SIBO eating plans. The plans vary, and so do individual results. But in general, they tend to recommend limiting carbohydrates. These include:

• Sugars and sweeteners.
• Fruits and starchy vegetables.
• Dairy products.
• Grains.

What happens if SIBO is left untreated?

Common symptoms of SIBO — including gas, bloating, abdominal pain and distension — are uncomfortable enough. But left unmanaged, SIBO can cause more serious complications with long-term consequences. Malabsorption of fats, proteins and carbohydrates can lead to malnutrition and vitamin deficiencies. In particular, vitamin B12 deficiency can cause nervous system problems and anemia. Poor calcium absorption can lead to long-term osteoporosis or kidney stones.

How is SIBO diagnosed?

The symptoms of SIBO overlap with many other gastrointestinal conditions, some of which you may already have. So when you seek a medical diagnosis, SIBO might not be the first thing your healthcare provider suspects. But if your symptoms and medical history suggest SIBO, your healthcare provider may suggest a breath test to verify it. This simple, noninvasive SIBO test measures hydrogen and/or methane levels in your breath to determine the presence of gas-producing bacteria in your gut. If your levels are above a certain number, it suggests an abundance of bacteria.

Your healthcare provider may suggest additional tests to look for signs of causes and complications of SIBO, including:

• Blood tests for vitamin deficiencies and blood protein deficiencies.
• A stool test (poop test) for excess undigested fats or bile acids.
• Imaging tests to check for structural problems.

What is the fastest way to cure SIBO?

SIBO is often a complication of another condition, and often causes complications of its own. When treating SIBO, healthcare providers need to address:

• The overgrowth itself.
• The complications of SIBO.
• The underlying cause.

A course of antibiotics is the standard medical treatment for bacterial overgrowth. Healthcare providers will then seek to manage your most acute complications. This might mean nutritional support and supplementation for vitamin and mineral deficiencies. It might mean a strict short-term eating plan to manage symptoms and then a modified longer-term eating plan to replenish your nutrition and keep bacterial overgrowth in check.

Ultimately, healthcare providers will want to locate and treat the underlying cause of your SIBO. This may require additional testing. If they suspect you have a motility disorder, they might prescribe motility agents to help stimulate the process and keep things moving. If they identify a structural problem, they might recommend surgery to correct it.

How can I prevent SIBO from recurring?

It’s common for SIBO symptoms to return several months after you’ve finished a course of antibiotics, especially if you have an underlying condition that predisposes you to SIBO. Antibiotics are a short-term SIBO treatment, but not a long-term solution. It’s important to try and address the underlying cause of your SIBO. Sometimes, that’s a separate medical condition you can manage more actively. Sometimes, it’s a structural problem you can address with surgery. You might need to adjust your existing medications or alcohol use to keep bacteria growth under control.

If you can’t identify or fix the underlying cause, you can try to manage bacterial overgrowth with a low-carb eating plan and probiotics. Studies on these solutions are inconclusive, but evidence suggests they may help. Especially as you’re nearing the end of your antibiotics, try to avoid overfeeding your bacteria with carbohydrates for a few weeks. Try to give your gut some new beneficial bacteria to balance the harmful ones by taking probiotics daily.

How long does SIBO last?

It depends on the amount of bacterial overgrowth in your small intestine. You may start to feel better within a few weeks of treatment. But you may need several months of treatment before SIBO goes away. Your healthcare provider can give you a better idea of your prognosis (outlook) based on your condition.

What’s a good eating plan to manage SIBO?

To try to get rid of SIBO, some healthcare providers recommend a short-term elimination diet. That means temporarily restricting all carbohydrates from what you eat to starve the bacteria. The more severe version of this is the elemental diet for SIBO, a liquid eating plan of pre-digested formulas. The elemental diet gives your gut bacteria nothing to digest while providing all the nutrition you need. Providers only prescribe it for short-term, therapeutic purposes.

A variety of other low-carb eating plans may work as an at-home elimination diet or maintenance plan. You may follow these short-term and then gradually add different foods back in, observing how your system responds. Or you may find that you thrive by sticking to an eating plan long-term. There are many kinds of low-carb eating plans and many of them claim to help with SIBO, including the Specific Carbohydrate Diet (SCD) and the Low FODMAP diet.

How do I know if I have SIBO or IBS?

SIBO and irritable bowel syndrome (IBS) share many symptoms, and it’s possible to have both. The main difference is that bacterial overgrowth can be clinically verified and treated. IBS, on the other hand, is a functional disorder that’s diagnosed when your symptoms can’t be clinically explained.

When you seek a medical diagnosis for your symptoms, you’ll probably be tested for SIBO as well as other comparable conditions, like lactose intolerance. If you test positive, you can be treated for those conditions, and hopefully, your symptoms will go away.

If they don’t all go away, you may have another condition. If no clear cause can be found, that’s when you’ll be diagnosed with IBS. Sometimes, IBS is found to be a contributing cause of SIBO.

A note from Cleveland Clinic

If you have gastrointestinal symptoms — bloating and gas, cramping and indigestion — you’ve probably tried to self-diagnose and discovered how tricky that can be. So many symptoms and conditions overlap that even common causes, like SIBO, can be hard to pin down. Medical testing can help sort out the causes of your distress. You can also learn a lot by adjusting your eating plan and observing how the changes affect your symptoms. For some people, a lifestyle change may be all it takes to manage symptoms of SIBO. If that isn’t enough, you may need antibiotics — but you’ll have to be careful to rebuild a healthy gut in the weeks that follow to prevent SIBO from recurring.