Small intestinal bacterial overgrowth (Often referred to as SIBO) is an imbalance of the bacteria in the small intestine, particularly types of bacteria that aren’t normally found in that part of the digestive tract. It’s also referred to as blind loop syndrome, which is an umbrella term for when food doesn't follow the normal digestion route and bypasses a section of the intestine.

SIBO can lead to uncomfortable symptoms like gas, bloating, and diarrhea. It can also inhibit the ability to digest and absorb nutrients from food. If you think you may be suffering from SIBO, consult your primary care physician right away.

What Are the Symptoms of SIBO?

Symptoms of SIBO vary from person to person and depend on the severity of the bacterial overgrowth as well as any coexisting conditions. Common symptoms of SIBO include:

• Bloating
• Diarrhea
• Constipation
• Gas
• Loss of appetite
• Vitamin deficiencies, including vitamin B12 deficiency
• Abdominal pain
• Unintentional weight loss

The type of bacteria that’s growing may also influence which symptoms you experience. Research suggests that methane-producing bacteria is associated with constipation, while hydrogen-producing bacteria is associated with diarrhea.

What Causes SIBO?

Doctors haven’t yet been able to determine a singular cause of SIBO, but they’ve found that some risk factors play important roles in the occurrence of the condition.

Age

Older people are at higher risk for developing SIBO, as they may make less of the gastric acid that breaks down food. Lower levels of gastric acid allow for the overgrowth of bacteria in the small intestine.

Stomach Anatomy

The structure of our digestive systems can undergo changes throughout our lives. These changes are often a result of damage or disease and can include gastric bypass surgery, diverticulosis, fistulas, and surgery to remove some or all of the colon and/or small intestine (called a colectomy). These structural changes can create an altered environment in which bacteria can thrive. One 2018 study found that people with colectomies are at a higher risk of developing SIBO. 

Low levels of stomach acid

When there isn’t enough stomach acid produced to break down food, bacteria can migrate further up the digestive tract than usual, as the environment is not acidic enough to kill them.

Certain medical conditions

Some diseases can slow how quickly food and waste products move through the small intestine. These conditions can include diseases both directly and indirectly related to the digestive system, including:

• Crohn’s disease
• Diabetes
• Scleroderma (a group of rare diseases that causes hardening and tightening of the skin, blood vessels, and digestive tract)
• Hypothyroidism
• Radiation enteritis (inflammation of the intestines that occurs after radiation therapy)
• Celiac disease
• Parkinson’s disease

Change in pH of the small intestine

The digestive system needs to maintain the balance of a specific pH in order to function properly, and different sections of your digestive tract operate at different pH levels. The pH balance of the small intestine allows for optimal nutrient absorption. Infections like Helicobacter pylori can damage your small intestine and throw off the pH balance. Interestingly, some studies have shown a correlation between SIBO and H. pylori infections.

How Is SIBO Diagnosed?

Diagnosing SIBO is generally done through one (or more) tests performed by a medical provider. In addition to specific SIBO tests, your doctor may recommend blood testing to look for vitamin deficiencies or a stool test to look for how well you’re absorbing fats; they may also have imaging tests done to look for any structural abnormalities in your digestive tract.

One way to evaluate for SIBO is the breath test, which measures hydrogen and methane levels in your breath. If these levels are high, it suggests a large number of gas-producing bacteria in your gut that could be attributed to SIBO.

Are There Treatments For SIBO?

There are several treatments available to treat SIBO, though the specific course of treatment will differ for everyone:

Antibiotics

Antibiotics are the most common treatment for SIBO, but a short course of antibiotic therapy can significantly reduce the total number of bacteria in your small intestine – this means both good and bad bacteria are removed. Removing good bacteria from your gut can cause some of the very symptoms you may be experiencing with SIBO, including digestive distress, gas, and bloating. And bacteria can return after you stop taking the antibiotic, so this isn’t a long-term solution. 

Probiotics

Probiotics – while popular and widely used for regulating gut flora – are a controversial treatment option for SIBO. While some studies have shown that probiotics are effective in treating the condition, others have shown that probiotics may cause SIBO.

If you’re interested in upping your probiotics intake, speak with your doctor. You can get probiotics in the form of supplements or by including probiotics-rich foods, like kefir, kimchi, and sauerkraut, in your diet.

SIBO diets

There is no one prescribed diet to treat or cure SIBO, but a popular option is the low-FODMAP diet. FODMAP stands for fructose, oligosaccharides, disaccharides, monosaccharides and polyols (sugar alcohols). These are short-chain carbohydrates (sugars) that are more difficult for some people to digest ‒ and they can ferment in the gut, leading to unpleasant digestive symptoms.

Some high FODMAP foods include:

• Fruits high in fructose (apples, cherries, mangoes)
• Nightshade vegetables (tomatoes, eggplant, peppers, white potatoes)
• Dairy products (cottage cheese, milk, ricotta, yogurt)
• Legumes (beans, peas, lentils)
• Wheat products
• Garlic and onions

What, how much, and even when a person eats is important when following a low-FODMAP diet. Working with a dietitian to implement dietary changes can make the transition less daunting. Health Coaches can also help you set long-term nutrition goals – especially when they have experience and credentials in nutrition. They can teach you how to listen to your body and learn what your unique needs are and how to meet them. 

The Bottom Line

While it isn’t always possible to prevent SIBO, you can work to take care of your gut health. Eating a healthy, well-balanced diet can help increase gut flora diversity and improve overall health and well-being. Avoiding cigarettes and other products with nicotine can also help prevent SIBO, as nicotine can change your gut flora. If you’re experiencing symptoms of SIBO or think you may have thrown off the bacterial balance of your digestive system, speak with your primary care physician.