Small intestinal bacterial overgrowth affects at least 39 million Americans and can bring about a range of uncomfortable digestive symptoms. The American College of Gastroenterology's (ACG) Clinical Guidelines for SIBO management state that dietary manipulation can be beneficial in treating SIBO. One such strategy is the SIBO Bi-Phasic Diet, a comprehensive and structured approach that combines food restriction with reintroduction. This article will delve into the fundamental principles, goals, and guidelines of the SIBO Bi-Phasic diet, helping to empower those with SIBO to navigate their journey to healthier digestion with dietary modifications.

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What Is SIBO?

In a healthy state, the bacterial population in the small intestine should be small. SIBO, or small intestinal bacterial overgrowth, is the excessive growth of bacteria in the small intestine. This bacterial accumulation can result from many reasons and causes maldigestion, malabsorption, and a leaky gut. Many digestive and extraintestinal symptoms are associated with SIBO, including bloating, gas, abdominal pain, heartburn, constipation, diarrhea, rashes, headaches, and fatigue. (3)

There are three distinct variations of SIBO: hydrogen-dominant SIBO, hydrogen sulfide-dominant SIBO, and intestinal methanogen overgrowth (IMO). The SIBO subtypes are determined through gas patterns measured on breath testing. IMO, previously called methane-dominant SIBO, occurs due to an overgrowth of microorganisms called archaea anywhere within the small or large intestines.

SIBO is closely related to irritable bowel syndrome (IBS). It is estimated that up to 80% of patients with IBS have SIBO underlying their symptoms (3). Furthermore, the type of SIBO present strongly influences the IBS subtype, with hydrogen- and hydrogen sulfide-SIBO linked to IBS-D and IMO associated with IBS-C.

What Is the SIBO Bi-Phasic Meal Plan?

The SIBO Bi-Phasic Diet (SIBO B-PD) is a dietary approach developed by Dr. Nirala Jacobi. It combines principles of the low-FODMAP and Specific Carbohydrate diets to manage and treat SIBO. The diet is divided into two phases (hence the name), each with specific dietary guidelines and objectives.

Understanding the Bi-Phasic Diet Plan

The first phase of the SIBO B-PD aims to restrict dietary fermentable carbohydrates to reduce the overgrowth of bacteria and their production of metabolic byproducts. Doing so can help to treat SIBO, relieve patients of SIBO symptoms, heal the gut, and restore optimal digestive function. During the second phase of the SIBO B-PD, antimicrobial agents are brought on board to remove the remaining bacterial overgrowth. At the same time, the patient begins to reincorporate foods into their diet. A personalized reintroduction approach helps patients identify trigger foods and maintain a healthy and balanced diet that supports gut health and prevents the recurrence of SIBO in the long term. (1)

Phases of the Bi-Phasic Diet

The SIBO B-PD starts with Phase 1, the restrictive phase. This lasts 2-6 weeks and aims to starve the bacteria and reduce their population in the small intestine. The restrictive phase guides the patient through a low-FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) diet, which involves avoiding or minimizing foods high in fermentable carbohydrates known to ferment in the gut and exacerbate symptoms. High-FODMAP foods include certain fruits, vegetables, grains, legumes, dairy products, sweeteners, and food additives. In addition to FODMAPs, the patient should avoid known trigger foods, even if they are low-FODMAP. This phase of the diet emphasizes eating smaller, frequent meals with adequate protein and healthy fat sources. (1)

Phase 2, or the reintroduction phase, starts after Phase 1 and lasts 4-6 weeks. The objective is for the patient to gradually reintroduce foods to expand the diet and identify their individual dietary triggers. Introductions should be performed in a controlled, systematic manner. Each food is reintroduced one at a time, and the patient should keep a food-symptom diary to track symptoms to determine how each food affects their body. (1)

Phase 2 naturally progresses into the final phase of the SIBO B-PD - the maintenance phase. The overall goal of the SIBO B-PD protocol is for the patient to create a sustainable, nutritious, and individualized dietary plan based on their tolerance levels. (1)

Implementing the Bi-Phasic Diet Plan

Implementing dietary changes, especially those involving extensive food elimination, can be intimidating and challenging. Here are tips and strategies for people planning to start the SIBO B-PD:

Preparation and Planning

Preparing for the SIBO B-PD ensures a smooth transition and maximizes its effectiveness. As with any therapeutic diet, consulting with a knowledgeable healthcare provider, such as a functional doctor or nutritionist who specializes in SIBO, before starting the diet is important. They can assess your specific condition, recommend and order SIBO testing if needed to tailor the treatment plan to your particular needs, and guide you through the protocol.

Meal planning and shopping is another important preparatory step. Familiarizing yourself with low-FODMAP food options and creating a meal plan for the restrictive phase will ensure success; a healthcare provider can help you do this. Shopping before starting the elimination diet to stock up on the necessary ingredients and clearing your kitchen of high-FODMAP and trigger foods will guarantee you have a clean slate to start the diet and helps you to avoid food temptations.

An elimination diet can be emotionally challenging. Food and social eating are a means of community, connection, and happiness for many people. Emotional preparation for the diet and finding a support network in friends, family, or support groups can ease the emotional shock of the diet's restrictive phase.

SIBO B-PD Phase 1

SIBO B-PD Phase 1 focuses on eating low-FODMAP and easily digestible foods. Here are examples of foods to include in the diet (2):

• Protein: poultry, beef, lamb, pork, fish, eggs
• Non-Starchy Vegetables: leafy greens, zucchini, bell peppers, cucumbers, carrots, eggplant, and bok choy
• Healthy Fats: olive oil, coconut oil, avocado, and moderate amounts of nuts and seeds
• Fruits: lemon, lime, berries
• Fermented Foods (as tolerated): cultured vegetables, sauerkraut, kimchi
• Beverages: water, herbal teas, black coffee

It's important to avoid or minimize the consumption of foods that can potentially worsen SIBO symptoms. Here are some foods that should be avoided during Phase 1 (2):

• Vegetables: onion, garlic, artichokes, asparagus, cauliflower, broccoli, Brussels sprouts, cabbage, potatoes, mushrooms
• Fruits: apples, apricots, figs, mango, peach, pears, plums
• Legumes: beans, soy (tofu, tempeh), peas
• Dairy: milk, yogurt, cheese, ice cream
• Grains: wheat (bread, pasta, pastries, cereals), barley, rye
• Sweeteners: sorbitol, xylitol, mannitol, high-fructose corn syrup, agave

For meal ideas and additional low-FODMAP resources, consider referring to Dr. Jacobi's three-month protocol handout, the SIBO Bi-Phasic Diet e-book, Monash University, and Rupa Health's Food Plans feature.

As patients begin implementing a low-FODMAP diet, they commonly experience die-off symptoms as the bacteria are cut off from their food supply. Staying well hydrated; eating smaller meals; chewing and swallowing food slowly and mindfully; keeping a journal to identify and avoid triggering foods; and engaging in stress-relieving activities can help manage uncomfortable digestive symptoms. Your doctor may also recommend digestive aids, such as digestive enzymes, digestive bitters, and carminative herbs, to provide additional symptomatic relief.

SIBO B-PD Phase 2

During Phase 2 of the SIBO B-PD, patients will systematically reintroduce higher-FODMAP foods into the diet. It is recommended to keep a diet-symptom journal during this process to help identify individual triggers, determine personal tolerances, and track progress.

The patient should be instructed to introduce foods one at a time and to begin by reintroducing generally well-tolerated foods that are less likely to trigger SIBO symptoms. These often include lactose-free dairy, gluten-free grains, and small amounts of fruits and vegetables. The introductions will be spaced several days apart, allowing the patient to accurately monitor the body's response to each food. Start with a small portion of each reintroduced food, and gradually increase the portion sizes as tolerated.

Remembering that this process is highly individualized, based on the patient's specific symptoms and sensitivities, is important. Staying in communication with their healthcare provider during this process can help patients to navigate the process effectively and guide them on specific foods that should be reintroduced or avoided based on needs and preferences.

Dietary Maintenance Considerations

After completing Phases 1 and 2 of the SIBO B-PD, adopting a long-term maintenance approach to manage SIBO symptoms, prevent a recurrence, and support gut health is essential.

As patients continue to incorporate more diversity into their diet through food introductions, they will naturally transition into a balanced and varied diet that includes a wide range of whole foods. Emphasizing nutrient-dense and anti-inflammatory options, like whole fruits, vegetables, lean proteins, whole grains, and healthy fats, encourages whole-body wellness and healthy digestion. Individual tolerances can change over time, so it can be helpful to occasionally rechallenge previous trigger foods to reevaluate food sensitivities and continue to diversify the diet.  

Also, remember that how you eat is just as important as what you eat regarding digestive health and function. Practice mindful eating habits, such as chewing food thoroughly, eating slowly, and paying attention to hunger and satiety cues.

Certain lifestyle factors can contribute to SIBO recurrence. Getting adequate sleep, staying physically active, avoiding excessive alcohol consumption, and implementing stress management techniques can optimize gut function and prevent SIBO recurrence.

Regular follow-up with a healthcare provider can also increase long-term success. Healthcare providers should continue to work with patients to address underlying medical conditions that increase SIBO risk and recommend gut-supporting supplements that maintain a healthy microbiome balance and intact intestinal barrier.

Monitoring Progress and Seeking Professional Guidance While on the SIBO Bi-Phasic Diet

Treating SIBO and maintaining healthy gut function requires an individualized approach, and everyone's progress on the SIBO B-PD will vary. Working closely with a healthcare professional, registered dietician, or nutritionist specializing in SIBO throughout the process is important to help accurately monitor progress and make necessary adjustments to the treatment plan.

Regular, subjective monitoring by the patient of their quality of life and digestive symptoms helps to gauge the effectiveness of the treatment protocol. Improvements in bloating, bowel regularity, abdominal pain, energy levels, mood, sleep quality, and ability to perform daily activities indicate that the treatment plan is working.

In some cases, objective measurements with laboratory tests may be required or helpful to monitor patient progress. These often include:

SIBO Breath Test

The SIBO breath test can monitor SIBO treatment progress and confirm SIBO eradication by tracking changes in hydrogen, methane, and hydrogen sulfide gas levels.

Comprehensive Stool Test

Other factors besides SIBO can contribute to digestive symptoms. A comprehensive stool test holistically assesses gut health by measuring markers that assess for inflammation, intestinal permeability, dysbiosis, intestinal infection, and maldigestion.

Food Sensitivity Panel

Definitively identifying food sensitivities and intolerances through observation alone can sometimes be difficult. A food sensitivity panel measures a person's immunological response to specific food proteins to identify foods that should be removed or limited from the diet at any point during the SIBO B-PD protocol.

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Summary

The SIBO Bi-Phasic Diet is one of many potential dietary approaches that can be incorporated into a treatment plan for managing and treating SIBO. This two-phase diet aims to address SIBO by targeting bacterial overgrowth through FODMAP elimination, followed by a reintroduction phase to identify individual trigger foods. By tailoring the diet to individual needs, closely monitoring symptoms, and working alongside informed healthcare professionals, individuals with SIBO can gain valuable insights into their dietary triggers, achieve symptom relief, and maintain long-term gut health.