Intestinal bacteria play a key role in the proper function of the digestive system ensuring the body digests and receives proper nutrients and vitamins. “Good” gut bacteria also help fight disease-causing microbe and parasites. The bacterial balance inside the gastrointestinal tract can be fragile, however, and overgrowth of even the good bacteria or their growth in the wrong place can lead to serious health consequences and symptoms such as maldigestion and malabsorption, bloating, gas, diarrhea, irregularity, and abdominal pain.
What is SIBO?
SIBO stands for Small Intestinal Bacterial Overgrowth and is also sometimes referred to as Bacterial Overgrowth in the Small Intestine (BOSI). It is defined as increase in the number and/or alteration of the type of bacteria in the upper GI tract – the stomach and small bowel. Normally, far fewer bacteria inhabit the small intestine than the ample growth found in the colon. Gastric acid secretion and intestinal motility keep the small intestine relatively free of bacteria. However, a wide range of abnormalities and malfunctions can encourage bacteria to multiply in the small intestine causing SIBO/BOSI.
What are the consequences of Small Intestinal Bacterial Overgrowth?
Bacterial overgrowth can inhibit nutrient absorption and lead to the following serious health problems:
- Altered intestinal permeability (leaky gut)
- Carbohydrate intolerance
- Malnutrition and weight loss
There are many individual conditions that are considered a separate diagnosis but have a common feature of bacterial overgrowth in the small intestine. Treating the overgrowth often relieves these conditions or at least helps prevent complications such as nutrient malabsorption due to disruption of the mucosal lining of the intestine. It is therefore important to assess bacterial overgrowth of the small intestine with any of these conditions. Some of these conditions are:
- Gastrointestinal disorders
- Irritable Bowel Syndrome
- Crohn’s disease
- Celiac disease
- Autoimmune processes such as hypothyroidism
- Functional disorders
- Restless Leg Syndrome
- Chronic Fatigue Syndrome
- Interstitial cystitis
What are the causes and predisposing factors of Small Intestinal Bacterial Overgrowth?
In order to overgrow, the bacteria need to be in the right environment where they can linger and receive enough nutrients. The following conditions often lead to such a hospitable environment for bacterial overgrowth:
- Loss of body’s natural antibacterial mechanisms
- Achlorhydria/hypochlorhydria: not enough hydrochloric acid produced by the stomach due to medication (PPI/H2 Blocker) use or other causes. Hydrochloric acid slows down bacterial growth.
- Immunodeficiency syndromes
- Loss of gastrointestinal tract’s ability to digest food
- Achlorhydria/hypochlorhydria – hydrochloric acid is necessary to break down food; otherwise it becomes available for the bacteria to feed on and grow.
- Low pancreatic enzyme secretion (pancreatic exocrine deficiency) means food is not broken down adequately so it lingers and feeds bacteria
- Decreased motility is a key factor for bacterial overgrowth making it easier for bacteria to colonize the small gut. Decreased motility can be caused by:
- Diabetes. Diabetics are much more prone to decreased motility
- Certain drugs such as opiates
- Surgeries that disrupt normal intestinal motility causing stasis
- Food poisoning that can lead to nerve damage in the small intestine leading to decreased motility and bacterial colonization
- Anatomical abnormalities such as outpouchings, either congenital or caused by surgery. They offer a surface area to bacteria to colonize and grow on.
- Radiation damage
- Cancer such as Lymphoma
What are the most common signs and symptoms of Small Intestinal Bacterial Overgrowth?
- Abdominal bloating
- Excessive gas or belching
- Abdominal cramps
- Steatorrhea (fats in stool)
- Nutrient deficiencies
- Weight loss
- Food and supplement intolerance
What are the long-term consequences of SIBO?
There are many serious consequences of Small Intestinal Bacterial Overgrowth especially if it’s left untreated for a long time.
- Vitamin B12 (Bacteria in the small intestine absorb vitamin B-12, which is essential for the normal functioning of the nervous system and the production of blood cells and DNA. A severe B-12 deficiency can lead to weakness, fatigue, tingling and numbness in your hands and feet, and, in advanced cases, to mental confusion. Damage to your central nervous system resulting from a B-12 deficiency may be irreversible.
- Calcium (Over time, damage to your intestine from abnormal bacterial growth causes poor calcium absorption, and eventually may lead to bone diseases, such as osteoporosis)
- Incomplete absorption of fats that leads to:
- Weight loss
- Fat-soluble nutrients (Essential Fatty Acids and Fat-soluble Vitamins. Bacteria in your small intestine break down the bile salts needed to digest fats, thus patients with SIBO often have poor fat absorption. As a result, your body can’t fully absorb the fat-soluble vitamins A, D, E and K.)
Damage to the intestinal lining – “leaky gut”
Toxins that are released when bacteria break down stagnant food harm the mucous lining (mucosa) of the small intestine. As a result, most nutrients, including carbohydrates and proteins, are poorly absorbed, leading to serious malnourishment while the breakdown of intestinal lining can lead to food sensitivities.
Are there reliable tests for Small Intestinal Bacterial Overgrowth?
The most commonly used test for SIBO is breathing test. It is simple and noninvasive and starts with you taking a small amount of a carbohydrate called lactulose in the form of a drink. Lactulose is not digested by the body and is only fermented by bacterial flora in the intestine. During the fermentation, the gases hydrogen and methane are produced, absorbed into the bloodstream and carried to the lungs. As lactulose travels down your intestine, different numbers and types of bacteria there produce different quantities of hydrogen and methane. Several samples of your breath are collected over a period of approximately 2 hours and analyze for the amounts and ratios of hydrogen and methane. These measurements help pinpoint the location of bacterial overgrowth and the types of bacteria responsible for it.
Are there additional tests for SIBO?
There are additional tests that may suggest the presence of Small Intestinal Bacterial Overgrowth although they cannot make a definitive diagnosis. These tests are:
- Comprehensive Digestive Stool Analysis. Elevation of some of the markers such as products of protein breakdown, fecal fats, and unexpected or extreme elevations in Beneficial SCFAs and n-butyrate may increase the likelihood SIBO is present.
- Cceliac and gluten sensitivity panel
- Nutritional testing
- B vitamin status
- Fatty acid profile
- Fat-soluble vitamin status
- Intestinal permeability panel for patients who may be experiencing intestinal lining damage (leaky gut) from long-standing SIBO
- Food antibody panel – also for patients with suspected leaky gut due to untreated SIBO
Are there other conditions that mimic Small Intestinal Bacterial Overgrowth?
Yes, a number of conditions may have a similar presentation:
- Pancreatic insufficiency
- Yeast overgrowth
- Parasitic infection
Testing and careful clinical evaluation usually help tell them apart.
How is SIBO treated?
Eliminating the underlying causes is an important step in treating Small Intestinal Bacterial Overgrowth. Some of the treatable underlying causes are:
- Maldigestion due to hypochlorhydria and pancreatic insufficiency
- Intestinal motility issues
- Poor diet (high starch / refined carbohydrates)
Depending on the breathing test results, your doctor may prescribe antibiotics Rifaximin and neomycin that have been shown effective in treating this condition.
Herbal-based antibacterial treatments have shown encouraging results in some studies although the improvement may take twice as long (30 days vs. 14 days) compared to antibiotic treatment and additional research is needed. Some of the common herbs and spices such as garlic, cinnamon and oregano contain antibacterial substances. Other botanical remedies that may be effective agains Small Bowel Bacterial Overgrowth are Hydrastis Canadensis. Origanum vulgare, Azadirachta indica and Allium sativum thanks to the substance called berberine that they contain.
Dietary interventions can help relieve the symptoms of SIBO. They include:
- Low FODMAP diet
- Low Carbohydrate diet
- Elemental diet (predigested carbs, proteins and fats that are easily absorbed)