Small Intestinal Bacterial Overgrowth (SIBO)
Small Intestinal Bacterial Overgrowth is the name used when the delicate balance of bacteria in the small intestines becomes unstable, and certain species begin to take over. This can cause a variety of symptoms that are often associated with IBS. Irritable Bowel Syndrome affects 11% of the population, and SIBO has been seen to be the cause in ~70% of cases.
Common Symptoms of SIBO
- Alternating constipation and diarrhea
- Abdominal cramping
- Abdominal pain and heat
- Behavioural issues
- Bloating and flatulence
- Burping and acid reflux
- Food sensitivities such as gluten, lactose, and fructose
- Joint pain and fibromyalgia
- Skin rashes, rosacea and eczema
- Iron, folate, and B12 deficiency
- Respiratory issues such as asthma
- Irritable bladder
- Restless legs at night
- Weight loss
What Causes SIBO?
Low Stomach Acid
Stomach acid is made from hydrochloric acid, potassium chloride, and sodium chloride, and is responsible for activating digestive enzymes to help break down food, and also to kill bacteria. You need a good production of gastric acid to signal the lower esophageal sphincter to close propelry. This sphincter connects the esophagus to the stomach (in the same fashion as the ileocecal valve). Low stomach acid can therefore cause food, gas, and acids to travel back up from the stomach.
If the stomach doesn’t have enough acid available when food enters, it can’t be broken down properly. This causes intact food particles to travel into the small intestine, which can trigger food intolerances, autoimmunity, and can provide an unbalanced substrate for bacteria in the small intestine to feast on. An open lower esophageal sphincter also allows bacteria to move from the stomach into the small intestine, which may also lead to dysbiosis and SIBO.
The prescription of antacids and proton pump inhibitors is extremely high in Australia, and are used to lower stomach acids. A systematic review found a direct association between PPI use and small intestinal bacterial overgrowth.
Bile Acid Insufficiency
Bile acids are made in the liver, and stored in the gallbladder. This slightly alkaline substance is squirted into the small intestine to help process dietary fats and fat soluble vitamins, processes cholesterol (roughly 500mg of cholesterol is converted to bile acids and eliminated each day), helps bind and excrete waste products such as bilirubin, and helps regulate the pH of the small intestines.
The small intestine is about 5-6 meters in length and has a surface area of 300m2. It’s full of trillions of bacterial species, which are very particular about the pH of their environment. Changes in this pH level can cause a reduction in some species, while others will flourish. Poor gallbladder function and bile acid formation can eventually lead to an overgrowth of bacteria, causing SIBO.
Of note, methylation is very important for the formation of bile acids, as it is required to synthesize choline and taurine, the 2 main nutrients needed for bile acid synthesis.
Migrating Motor Complex
The Migrating Motor Complex (MMC) is an ingenious process involving a cleansing wave of electrical activity that triggers peristalsis in the small intestines every 90 minutes. This generally happens between meals, and can be encouraged through the night while sleeping, or during other periods of fasting. That feeling of your stomach rumbling when you’re hungry is actually your MMC in full swing.
The function of the MMC is to clear out accumulated bacteria from the small intestines, and propel them into the large intestines (through the ileocecal valve). If there are errors with this system, bacteria have an opportunity to grow and proliferate in the small intestines.
Ileocecal Valve Dysfunction
The ileocecal Valve is the small sphincter of muscle that connects the small intestines to the large intestine. About 2 litres of fluid passes through this valve into the colon each day. The tone of this sphincter is critical for preventing a backwash of bacteria from the large intestine back into the small intestines.
The signalling mechanism to the ileocecal valve can be obstructed in cases of autoimmunity, food poisoning, E.coli, Salmonella, Shigella, or Campylobacter overgrowth, or when pressure is put on this valve from a large amount of gas. This causes the valve to open, allowing bacterial migration to occur.
Assess your Ileocecal Valve
- Do you feel an intense amount of pressure under your ribs, pressing up like a balloon (referred pain)?
2. Do you have back pain on the lower right side (referred pain)?
3. Do you have right shoulder pain (referred pain)?
4. Do you have dull pain inside your right hip bone that is tender to the touch (at the location of the ileocecal valve)?
Other Causes of SIBO
Overconsumption of processed carbohydrates has been associated with bacterial overgrowth, and also a diet low in resistant starch. Resistant starch is the food for bacteria, which helps them grow and proliferate. Regular consumption of this starch increases bacterial diversity and provides a foundational balance to the microbiome. Paleo and a ketogenic diets tend towards lower resistant starch, and need to be considered if used long term.
Medications such as morphine, calcium channel blockers, and narcotics can cause SIBO, as can high alcohol intake, and prolonged stress. Stress depletes minerals that are needed to create stomach acid. Bowel surgery, coeliac disease, diabetes, scleroderma and diverticulitis are also sources for bacterial overgrowth.
Importance of Testing
SIBO is tested via breath testing, which can be done in your home. This involves drinking a glucose and lactulose solution (on different days), and providing breath samples every 20 minutes for 3 hours. These sugars should move through the small intestine within 100 minutes (depending on your personal transit time), and should not be affected by bacteria. If there is an overgrowth, the sugars will feed that bacteria and cause an increase in either hydrogen or methane gas levels (or both).
The gas level on your test result will determine how severe your overgrowth is, and how long it will take for eradication. It will also dictate the type of treatment required. Methane-producing SIBO and hydrogen-producing SIBO both respond to different treatment strategies.
As mentioned, antibiotics are a treatment option and should be discussed with your doctor. Antimicrobial herbs are very effective for SIBO, but require a longer treatment period than antibiotics. Choosing the right antimicrobial herbs for the specific type of SIBO you have is very important.
Other aspects that need to be considered are dietary intervention, correcting bile acid function, reintroducing beneficial bacteria into the system, reigniting the migrating motor complex, getting the bowels moving regularly, alkalising the system during eradication, introducing prebiotics to feed beneficial bacteria, and healing and conditioning the gut.
If you have symptoms that may indicate SIBO, a good first step is to do the SIBO Quiz. I generally find scores over 80 correlate with SIBO, but should be followed up with testing to confirm. This can be done in the privacy of your own home via breathe testing.