Small Intestinal Bacterial Overgrowth (SIBO) is a condition where an unusually high number of bacteria reside in the small intestine, which typically has fewer bacteria compared to the large intestine. When these bacteria ferment carbohydrates, they produce gases, leading to symptoms like bloating, abdominal discomfort, and altered bowel habits. A common method for diagnosing SIBO involves a breath test, which measures these gases. Proper preparation, particularly through dietary adjustments, is essential for accurate test results.
The Purpose of the Pre-Test Diet
The primary goal of this preparatory diet is to reduce the activity of bacteria and clear residual fermentable carbohydrates from the small intestine. This process helps to “starve” the bacteria, ensuring that any gas detected during the test truly reflects an overgrowth, rather than gas produced from recently consumed foods.
The breath test measures hydrogen and methane gases that bacteria produce when they interact with a sugar solution, such as lactulose or glucose, given during the test. If the small intestine contains leftover fermentable foods, these could be metabolized by existing bacteria, leading to artificially elevated gas levels and potentially a false positive result. Different SIBO tests may have slightly varied dietary instructions, but the underlying principle of reducing bacterial fuel remains consistent.
Foods to Avoid
Foods high in fermentable carbohydrates, often referred to as FODMAPs, should be strictly avoided as they can feed bacteria and produce gas. This includes many common items like grains such as bread, pasta, and whole-grain cereals, along with most fruits and vegetables. Vegetables, especially cruciferous types like broccoli and cauliflower, and legumes such as beans and lentils, contain fibers that can ferment.
Dairy products, including milk, cheese, and yogurt, are typically excluded due to their lactose content, a fermentable sugar. Processed foods, sugary drinks, and anything containing high amounts of sugar, corn syrup, or artificial sweeteners are also prohibited. Nuts, seeds, and even certain condiments and spices (beyond salt and pepper) are generally not permitted because they can contribute to bacterial activity or leave residues in the digestive tract.
Foods to Include
The pre-test diet focuses on low-fiber, easily digestible foods that minimize bacterial fermentation in the gut. Plain cooked meats, such as chicken, fish, or other poultry, are generally permitted, provided they are baked, broiled, or grilled and seasoned only with salt. Eggs are also a safe option for protein.
Plain white rice is typically allowed as a carbohydrate source, but other grains like brown rice or whole wheat products are excluded due to their higher fiber content. Clear meat-based broths, made without vegetables or bone/cartilage, can provide some hydration and nutrients. Certain fats and oils, including coconut oil, olive oil, vegetable oil, butter, and lard, are usually acceptable.
Beyond Food What Else to Consider
Beyond dietary adjustments, several other factors are important for accurate SIBO test preparation. A fasting period of 8 to 12 hours is typically required immediately before the test, during which only plain water is allowed. This ensures the digestive tract is clear of food residues. Most individuals find it convenient to schedule the test for the morning, aligning the fasting period with overnight sleep.
Medication instructions are also important; healthcare providers often advise stopping antibiotics for at least two to four weeks prior to the test, and probiotics for about one week. Laxatives, motility drugs, and certain antacids may also need to be discontinued several days or a week before the test. It is advisable to avoid smoking and strenuous exercise for at least one hour before and during the test, as these activities can influence breath gas levels. Always follow the specific instructions provided by the healthcare provider or testing facility, as protocols can vary.