Small Intestinal Bacterial Overgrowth (SIBO) is a condition characterized by an excessive amount of bacteria populating the small intestine. Diagnosis is confirmed using a SIBO breath test, a non-invasive procedure measuring the hydrogen and methane gases produced after consuming a specific sugar solution (lactulose or glucose). The accuracy of the results relies entirely on strict adherence to a preparatory protocol to ensure clear baseline readings and prevent false results.
The Purpose of Pre-Test Dietary Restrictions
A restricted diet is required for 24 to 48 hours leading up to the test to effectively “starve” the existing bacteria in the small intestine. This preparatory phase minimizes fermentable carbohydrates, such as FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) and other complex sugars, that these bacteria typically consume. The diet is limited to simple, low-fiber foods, such as plain steamed white rice, lean meats, and eggs.
By removing these food sources, the bacteria are cleared out, ensuring the only substrate available for fermentation during the test is the diagnostic solution. Consuming fermentable foods too close to the test can elevate the baseline breath reading, potentially leading to a false positive result. This allows the sugar solution to be the sole trigger for gas production, enabling clinicians to accurately measure the gas curves.
Specific Guidelines for Olive Oil and Other Fats
Pure fats, such as olive oil, coconut oil, butter, and lard, are generally permitted during the 24- to 48-hour preparatory diet phase. Fats are composed of triglycerides and do not contain fermentable carbohydrates or sugars that would feed the bacteria, meaning they do not interfere with the test.
However, the amount and timing of fat consumption require careful consideration. Ingesting large quantities of any fat can significantly slow down gastric emptying and gut motility. This delay can potentially skew the test results by altering when the diagnostic solution arrives in the small intestine.
The standard protocol allows small amounts of these pure fats for cooking or seasoning during the preparation day, but they must be stopped completely during the final fasting period. Patients should only use allowed fats to prepare the limited list of foods. Always confirm specific allowance guidelines with the testing provider, as protocols can vary.
The Final Fasting Phase and Medication Restrictions
The final 12-hour complete fast immediately precedes the test. During this window, no food, chewing gum, mints, or caloric beverages are allowed; only plain, unflavored water may be consumed. Strenuous exercise or smoking must be avoided for at least an hour before and throughout the test, as these activities can affect breath samples.
In addition to dietary restrictions, certain medications and supplements must be discontinued because they can interfere with the gut microbiome or motility. Oral antibiotics and antifungals require the longest washout, typically two to four weeks. Probiotics and laxatives, which affect transit time, are commonly stopped for at least one week prior to testing.
Other agents, such as proton pump inhibitors (PPIs) and pro-motility drugs, may need to be discontinued several days before the test, depending on the provider’s instructions. Patients must consult with their prescribing physician before stopping any necessary medication. The goal of these restrictions is to ensure the small intestine environment is neutral for an accurate diagnostic test.