What foods are allowed on the SIBO test?

December 24, 2025 •

4 min read

Many patients report feeling confused about the specific dietary guidelines before a SIBO breath test, a critical factor for accurate results. Knowing what foods are allowed on the SIBO test and what to avoid is essential to properly starve gut bacteria and prevent false readings.

Quick Summary

The pre-test SIBO diet is a low-fermentation plan followed for 24-48 hours, featuring plain proteins and white rice, followed by a 12-hour fast. This preparation helps ensure the breath test accurately measures bacterial overgrowth by limiting fermentable carbohydrates.

Key Points

The "White Diet": Before a SIBO test, you must follow a restrictive, low-fermentation "white diet" for 24-48 hours to starve gut bacteria and reduce background gas.
Allowed Foods: Permissible foods include plain proteins like baked chicken, fish, or eggs, clear meat broth, plain steamed white rice, and simple fats like olive oil and butter.
Foods to Avoid: You must avoid high-fiber foods, whole grains, fruits, vegetables, legumes, nuts, seeds, and most dairy products.
Pre-Test Fasting: A 12-hour complete fast, with only water allowed, is required immediately before the test to clear all residual food from the digestive system.
Medication and Supplement Holds: It is necessary to stop antibiotics, probiotics, herbal antimicrobials, and certain supplements well in advance of the test.
Lifestyle Restrictions: To ensure accurate readings, avoid vigorous exercise and smoking for at least one hour before and during the test.

The Small Intestinal Bacterial Overgrowth (SIBO) breath test is a diagnostic tool used to measure hydrogen and methane gas produced by bacteria in the small intestine after consuming a sugar solution. To ensure the most accurate results, patients must adhere to a specific, restrictive diet for 24 to 48 hours prior to the test. This preparation phase is often called the "white diet" because it focuses on simple, low-fiber foods that do not feed the gut bacteria, effectively clearing the digestive tract of fermentable material. This article provides a comprehensive guide to what foods are allowed on the SIBO test and the full preparation protocol.

The SIBO Pre-Test "White" Diet

The goal of this temporary, restrictive diet is to starve the bacteria in your gut, forcing them to produce the baseline gas levels that the breath test measures. This prevents false positives from recently consumed, highly fermentable foods.

Allowed Foods for SIBO Test Prep

Proteins: Unseasoned baked or broiled white meat chicken, turkey, and fish. Eggs are also permitted. Plain, clear meat broth made from meat only (no bone, cartilage, or vegetables) is acceptable. For vegetarians or vegans, some protocols may allow tofu or eggs, but this should be confirmed with your healthcare provider.
Carbohydrates: Plain, steamed white rice is the primary source of carbohydrates. Avoid brown rice, basmati, or other whole grains due to their higher fiber content. Some guidelines also permit plain white sandwich bread.
Fats and Oils: Small amounts of simple fats like coconut oil, olive oil, butter, or ghee are allowed for cooking.
Seasoning: Only use salt and pepper. All other herbs, spices, or seasoning blends should be avoided.
Beverages: Plain water is the only consistently allowed beverage. Weak black coffee and/or weak black tea, without any added sugar, sweeteners, milk, or cream, may be permitted up until the final fasting period.

Foods to Strictly Avoid

Adherence to the "do not eat" list is just as important as following the "allowed" list. Avoiding these foods helps prevent inaccurate test results.

Fruits and Vegetables: All fresh, canned, dried, or juiced fruits and vegetables are prohibited. This includes starchy vegetables like potatoes.
Grains: Any whole grain products, including whole wheat, bran, pasta, cereal, and brown rice, are not allowed.
Dairy: All dairy products, including milk, cheese, yogurt, and ice cream, should be avoided, with the exception of eggs and sometimes hard cheeses like parmesan.
Legumes, Nuts, and Seeds: All beans, lentils, nuts, and seeds are forbidden.
Sugars and Sweeteners: Avoid all forms of sugar, high-fructose corn syrup, honey, and artificial sweeteners.
Processed Foods: Cured or brined meats (like deli meat, sausage, and lox), and anything with added sugars, brines, or complex seasonings must be avoided.
Fermented Foods: Kombucha, sauerkraut, yogurt (not allowed anyway), and other fermented items are prohibited.
Beverages: Juices, soda, alcohol, and herbal teas should not be consumed.

Timeline for SIBO Test Preparation

Following the correct timeline is crucial for test accuracy. The preparation involves two main stages: a dietary restriction period followed by a fasting period.

24-48 Hours Before the Test: Begin the strict low-fermentation "white diet" as prescribed by your doctor. The length may be extended to 48 hours for patients with slow motility or chronic constipation. During this time, you must stop taking all probiotics, laxatives, and non-essential medications and supplements, as advised by your doctor.
12 Hours Before the Test: A complete fast is required. This means nothing to eat or drink except plain water. No coffee, tea, gum, or mints.
The Morning of the Test: Avoid all food and drink except water. You can brush your teeth but must avoid swallowing toothpaste. Do not smoke or exercise vigorously for at least one hour before the test.

SIBO Test Prep Comparison: White Diet vs. Final Fasting


Feature	White Diet (24-48 Hours Pre-Test)	Final Fasting (12 Hours Pre-Test)
Purpose	Reduces fermentable carbohydrates to lower background gas levels	Clears residual food and drink to establish a true baseline
Food Allowed	Plain protein (meat, fish, eggs), white rice, white bread, broth, oils, salt, pepper	None
Drinks Allowed	Water, weak black coffee, weak black tea (no additives)	Only plain water
Typical Duration	24-48 hours (depending on motility)	12 hours (usually overnight)
Key Action	Follow a restrictive diet, stop supplements/meds	Abstain from all food and drinks besides water

Additional Pre-Test Considerations

Beyond diet and fasting, other factors can influence the accuracy of a SIBO breath test:

Medications and Supplements: As mentioned, many items need to be stopped in advance. Antibiotics and herbal antimicrobials should be stopped several weeks prior, while probiotics should be discontinued at least one week before. Always consult your prescribing physician before stopping any essential medication.
Vigorous Exercise and Smoking: Both can affect breath gas levels. Avoid them for at least one hour before and during the test.
Mouthwash: Do not use mouthwash before or during the test, as it can affect the bacteria in your mouth and lead to inaccurate readings.
Health Conditions: Diabetic patients should consult their doctor before fasting. It is also not recommended to test during an active infectious illness.

For a detailed overview of the test procedure and preparation, you can refer to authoritative sources like QuinTron Breath Testing.

Conclusion

The strict preparation diet for a SIBO test, while challenging, is a necessary step for achieving an accurate diagnosis. By limiting your intake to simple, non-fermentable foods like plain proteins, white rice, and clear broth for 24-48 hours, and then fasting completely for 12 hours, you ensure the bacteria have nothing to feed on. This allows the breath test to precisely measure the gases produced by existing bacterial overgrowth, providing reliable results to guide your treatment plan. Always follow your doctor's specific instructions for the most effective test outcome.

Frequently Asked Questions

No, you must avoid all vegetables, including starchy ones like potatoes, during the 24 to 48-hour SIBO prep diet. Vegetables are high in fermentable carbohydrates that can interfere with test results.

Weak black coffee or black tea, without any added milk, cream, or sweeteners, may be consumed during the initial 24-hour prep diet. However, all beverages except plain water are forbidden during the final 12-hour fasting period.

If you eat the wrong food, you will likely need to reschedule the test. Eating fermentable foods can lead to inaccurate breath readings, potentially causing false positive or negative results.

No, only plain, steamed white rice is permitted. Other rice varieties, such as brown rice or basmati, contain higher levels of fiber and starch that feed bacteria and can distort the test's outcome.

Most medical guidelines recommend stopping all probiotic supplements at least one week before the SIBO breath test to prevent them from interfering with the microbial activity being measured.

Yes, but with careful planning. While the standard diet includes animal protein, vegetarians and vegans can sometimes use alternatives like tofu or eggs for protein. Always consult your practitioner for approved options.

The 12-hour fast is crucial to clear any undigested food and residual debris from your digestive tract. This ensures the test accurately captures a true baseline of gas production before the test substrate is introduced.

Yes, small amounts of simple fats such as butter, olive oil, coconut oil, or ghee are typically allowed for cooking during the preparation diet. They contain no fermentable carbohydrates that would affect test results.