SIBO Basics
Small intestinal bacterial overgrowth (SIBO) occurs when there is an overgrowth of bacteria, particularly the wrong kind in the wrong place, of the small intestine. This can lead to symptoms of low appetite, early satiety, nausea, gas, bloating, diarrhea, abdominal pain, malnutrition or weight loss. Irritable bowel syndrome (IBS) is often caused by SIBO.
The small intestine normally has a small population of bacteria in it due to the rapid movement of food stuff through the intestine, combined with the presence of bile acids. Sluggish movement of the intestine is thus one risk factor for SIBO. In addition to symptoms, SIBO may cause poor absorption of nutrients.
SIBO Test Preparation
Courses of antifungals and antibiotics must be completed two weeks before the test.
SIBO Test Preparation Diet
This diet is 24-48 hours prior to your SIBO Test. During this test, stop all non-essential medications, supplements and probiotics. Your provider will be able to assess this.
The bacteria will be starved for the 24-48 time period with this dietary protocol. As a result, they will react to the lactulose solution, yielding more accurate test results. There are small amounts of lactose in the lactulose solution. If you experience severe reactions to lactose, consult this with your provider.
Consume These Foods During the 24-48 Hours Prior to Your SIBO Test
- Non-processed meat, poultry, fish or seafood
- Plain, steamed white rice
- Eggs
- Clear meat broth (homemade without bone, cartilage or vegetables)
- Fats/oils
- Salt and pepper
- Plain, weak black coffee or plain, weak black tea
- Plain water
Alcohol, Tobacco and Marijuana
Eliminate chew tobacco, edible marijuana products and alcohol during the 24-48 hour preparation diet. Eliminate smoking tobacco and marijuana at least one hour prior to the test and throughout the duration of the test.
12 Hours Prior to the Test
You will need to be fasting 12 hours before the test. It is recommended to fast overnight (ie 7:00 pm-7:00 am).
One hour Prior to the Test
Wake at least one hour before the test. You may brush your teeth and drink plain water. Do not consume food/coffee/tea, exercise vigorously nor smoke before the test.
During the Test
Once the dietary protocol has been completed, you are ready to take the test. Fill out all of the labels, except for the collection time, and place them lengthwise on your ten test tubes. Mix your lactulose solution with eight ounces of water. Let it sit while you take your baseline test.
Breathe in normally, exhale into the collection device, mid-breath place your test tube on the needle, wait two seconds then take the test tube off the needle. Write the time on the test tube.
Now, drink the prepared lactulose solution, and write down the time you finished drinking the solution (ie 8:00 am). Set alarms at twenty minute intervals to collect samples (ie 8:20 am, 8:40 am, 9:00 am, etc.). You need to collect seven samples within the first two hours. Repeat the collection process with each test tube. Breathe in normally, exhale into the collection device, mid-breath place your test tube on the needle, wait two seconds then take the test tube off the needle. Write the time on the test tube. Make sure you only puncture each test tube once.
Please note that some individuals experience SIBO symptoms during the test. You may record these symptoms on the Patient Record.
After Taking the Test
Pack away the test tubes in the bubble wrap. Place the test tubes and Patient Record in the box to ship off to the lab. You may resume your normal dietary pattern.
SIBO: Dysbiosis Has a New Name
One of the best review articles by Steven Sandberg-Lewis, ND, DHANP and Allison Siebecker, ND, MSOM, from The Townsend Letter
A Breath of Fresh Air, Editorial by Dr Joseph Sellin, Clinical Gastroenterology and Hepatology Vol. 14, No. 2
Insight into some of the pitfalls and uncertainties of SIBO testing.
Vegetarian SIBO Diet
Vegetarian SIBO Bi-Phasic Diet
SIBO Substrates to Test
When conducting Small Intestinal Bacterial Overgrowth (SIBO) testing, different substrates (e.g., lactulose, fructose, inulin, and sorbitol) are used to measure the production of gases such as hydrogen, methane, and sometimes hydrogen sulfide. These gases are produced by gut bacteria fermenting the substrate.
Substrates and Gases:
- Lactulose:
- Gases produced: Hydrogen, methane.
- Food group representation: Lactulose is a synthetic sugar, not naturally occurring in foods. It tests overall bacterial fermentation and transit time through the small intestine.
- Fructose:
- Gases produced: Hydrogen, methane.
- Food group representation: Found in fruits, honey, and high-fructose corn syrup. It represents fructose in the carbohydrate category.
- Inulin:
- Gases produced: Hydrogen, methane.
- Food group representation: A fermentable fiber (prebiotic) found in foods like garlic, onions, asparagus, and chicory root. It represents fermentable fibers and oligosaccharides.
- Sorbitol:
- Gases produced: Hydrogen, methane.
- Food group representation: A sugar alcohol found in some fruits (e.g., apples, pears, and cherries) and used as a sweetener in sugar-free products. It represents polyols in the FODMAP category.
Connection to Food Groups:
These substrates mimic certain carbohydrates or fermentable compounds from food. The gases detected during testing indicate how gut bacteria ferment these substances, which helps diagnose SIBO or assess malabsorption.
- Lactulose: General carbohydrate fermentation.
- Fructose: Monosaccharide fermentation.
- Inulin: Prebiotic fiber fermentation.
- Sorbitol: Sugar alcohol fermentation.
Each test provides insights into how specific groups of fermentable carbohydrates (often referred to as FODMAPs) affect bacterial activity in the gut.
Test Results
High levels of hydrogen or methane during a SIBO (Small Intestinal Bacterial Overgrowth) test indicate abnormal fermentation of the test substrate by bacteria in the small intestine. Here’s what each gas signifies:
High Hydrogen Levels
- Cause: Hydrogen is primarily produced by fermenting bacteria when they metabolize carbohydrates in the gut.
- Significance:
- Suggests the presence of SIBO with bacteria fermenting the test substrate (e.g., lactulose or glucose) in the small intestine.
- Associated with symptoms like diarrhea, bloating, and abdominal pain.
- Often linked to rapid transit through the intestines, as the fermentation process happens early.
High Methane Levels
- Cause: Methane is produced by specific gut microorganisms called methanogens (e.g., Methanobrevibacter smithii), which consume hydrogen and convert it to methane.
- Significance:
- Indicates methane-dominant SIBO.
- Commonly associated with constipation rather than diarrhea (referred to as “methane-dominant SIBO” or “IMO” – Intestinal Methanogen Overgrowth).
- Methanogens may slow gut motility, exacerbating symptoms of constipation.
Mixed Hydrogen and Methane Elevation
- Indicates the presence of diverse bacterial and methanogen populations in the small intestine.
- May cause mixed symptoms, including bloating, discomfort, and alternating diarrhea/constipation.
Clinical Interpretation
- Early rise in gas production (within 90 minutes): Suggestive of SIBO, as the substrate reaches the small intestine before transit to the colon.
- Late rise in gas production: Likely due to normal fermentation in the colon, not SIBO.
The specific gas pattern can guide treatment:
- High hydrogen: Treated with antibiotics like rifaximin.
- High methane: May require a combination of rifaximin and neomycin for better efficacy against methanogens.
