Bi-Phasic Diet For SIBO: The Ultimate Guide (2022)

Phase 1: Reduce and Repair (4-6 weeks)

In phase 1, foods are broken down into three columns labeled, ‘Restricted Diet,’ ‘Semi-Restricted,’ and ‘Avoid.’ An example can be seen below. 

Jacobi recommends that those who start on the diet begin only with the foods in the restricted column and move to include foods on the semi-restricted column once symptoms subside. She notes that adding in semi-restricted foods may happen within the first week if there is enough symptom improvement, though others may require a restricted diet for the entire 6 weeks of phase 1.

The semi-strict version of phase 1 allows for some starches such as rice or quinoa to be added back into the diet. Jacobi suggests reverting to the strict version of the phase 1 diet if following the semi-strict version produces symptoms.

Phase 2 Remove and Restore (4-6 weeks) 

Phase 2 becomes mildly less strict with foods broken down into two columns: ‘Phase 2 Diet’ and ‘Avoid.’ All foods allowed in phase 1 are allowed in phase 2. Additions to phase 2 include potatoes (½ cup), raw cacao (1 tsp), and various condiments such as fish sauce, miso, and tamari.

The ‘remove’ refers to removing bacteria, and ‘restore’ refers to restoring motility. Phase 2 is designed to include practitioner-prescribed antimicrobials. Promotility agents might also be prescribed during this phase to improve small intestinal motility and to prevent SIBO recurrence. 

Summary of Available Evidence 

Like the SSFG diet, there is no research proving the efficacy of this approach for SIBO treatment. Studies have been conducted on the low FODMAP diet and the SCD for other disease processes. However, these diets have not been studied explicitly for their use in SIBO management or treatment. 

What we like about the Bi-Phasic Diet

Professional Oversight

One of the biggest pros to the Bi-phasic diet is that the diet is clearly intended to be carried out under professional  supervision. This point is made clear as Jacobi suggests checking in with a practitioner regarding symptom control when adding in semi-restricted foods in phase 1. We believe medical oversight is important when undergoing any elimination diet, so we were pleased to see oversight built into the program.

More Structure and Fewer Restrictions than the SSFG

The Bi-phasic diet offers more clear time parameters for the 2 diet phases. The diet also skips out on the highly restrictive introductory diets found in the SSFG and SCD diet. We feel the introductory diet in both the SSFG and SCD is lacking scientific support and could potentially lead to malnutrition, so we were happy to see this approach excluded from the Bi-phasic diet. We also liked how the diet works to liberalize the intake of certain starchy foods such as quinoa or rice as early as the first week depending on the degree of symptom control.

Attention to Dosing

The diet pays attention to the dosing of foods unlike the SCD, which we feel allows for slightly more diet diversity, while limiting gut irritants at doses where they may become more problematic. 

Highlighting the Importance of Dietary Fiber

Jacobi points out the importance of fermentable dietary fiber for promoting the health and wellness of the microbiome. She states that the goal of treatment is to eventually reintroduce these fibers again. This is an important point on which we agree, and we were happy to see this mentioned in the description of the Bi-phasic diet. However, we also would’ve preferred to see more clear parameters after phase 2 of the diet for the reintroduction of foods containing fermentable fibers. 

What we don't like about the Bi-Phasic diet

Presented as a Treatment

Our perception when examining the Bi-phasic diet was that the diet was a treatment for SIBO, however no scientific evidence is available to substantiate this. We believe the diet should only be presented as a possible symptom management aid until studies are available to support the use of the diet as a legitimate treatment option.

May Delay the Use of Clinically Validated SIBO Treatments

According to the American College of Gastroenterology, the use of antibiotics is the cornerstone therapy for the treatment of SIBO. S In general, a single 7- to 10-day course of antibiotics improves symptoms for up to several months in 46%–90% of patients with SIBO and results in negative breath test results in 20%–75% of cases. S

While the evidence for antibiotics in SIBO treatment is primarily of poor to modest quality,S this is still leaps and bounds above the level of evidence supporting the use of the Bi-phasic diet, which is currently none. We were concerned to see phase 1 of the diet being suggested prior to the use of antimicrobial strategies in phase 2 for several reasons.

To begin, this recommendation gives the impression that phase 1 of the diet is sufficient to begin treatment of SIBO when supporting evidence is not available to suggest this is the case. Also problematic is that SIBO patients are at heightened risk of malnutrition at baseline, so adding on a restrictive diet before the use of a more validated treatment approach might enhance the risks of malnutrition.

We would cautiously opt for the use of validated treatments first before the trial of an unproven diet strategy and would be especially mindful to monitor for and treat any underlying nutritional deficiencies before suggesting a restrictive diet therapy. Likewise, we would only suggest the use of diet as a symptom management aid given the total lack of evidence supporting the use of most dietary measures as a SIBO treatment.

Combining Antimicrobials with the Reintroduction of Foods

We weren’t wild about the idea of validated therapies potentially being delayed due to the structure of the Bi-phasic diet protocol. However, we were especially not thrilled to see antimicrobial therapies combined with the reintroduction of foods during a more lenient phase of the diet.

Phase 2 of the diet is not particularly different from the combined restricted and semi-restricted diet in phase 1. However, it could be possible that someone remains on the fully restricted diet in phase 1 for the first 6 weeks. If this were the case, it might be possible that several new foods would be introduced in phase 2 in tandem with the prescribing of antimicrobials.

Antimicrobials often result in gastrointestinal symptoms such as diarrhea. Symptoms generated by antimicrobials can overlap with common symptoms produced by diet intolerances. We have concerns that the Bi-phasic diet is not structured appropriately to spot specific diet intolerances or sensitivities. It’s possible this could be exacerbated if reactions to antimicrobials are misconstrued by patients as a diet intolerance after adding back more dietary leniency.

Avoid “Until Further Notice”

While the second phase of the diet is mildly more lenient than the first, the diet is still highly restrictive in the final phase. Phase 2 eliminates several foods including most grains, several fruits, most legumes, chia seeds, flaxseeds, and even soy sauce and certain oils. From what we can tell, these foods are to be avoided “until further notice”, and we see no instructions for reintroducing or testing these foods for provoking symptoms. We find this concerning. While the diet is much more structured than the SSFG, the end result is another diet strategy that lacks clear reintroduction parameters. We feel the bi-phasic diet could potentially lead to scarring of the microbiome in ways that may or may not be favorable. The diet may also remain unnecessarily restrictive which could increase risks for malnutrition, disordered eating patterns, and lower quality of life.

Our verdict

• Like the SSFG, the Bi-phasic diet further restricts fermentable carbohydrates compared to the low FODMAP diet and the SCD.
• The Bi-phasic diet is less restrictive during the initial phase than the SSFG or the SCD and allows for more prompt diet liberalization based on symptom control in phase 1.
• We liked that the Bi-phasic diet is designed to include the oversight of a professional. We also liked that the diet adds more structure than what is found in the SSFG.
• We appreciated how Jacobi emphasized the importance of fermentable fiber for the microbiome, and how the Bi-phasic diet accounts for the dosing and serving sizes of potential gut irritants.
• We disliked that the diet was presented as a treatment when no supporting evidence is available proving this claim. 
• We believe that delaying antimicrobials to phase 2 of the diet is not a substantiated practice given that antibiotics are the cornerstone/validated treatment for SIBO. 
• We have concerns that the structure of the Bi-phasic diet might delay treatment with a more validated approach while enhancing risks for malnutrition due to the restrictive nature of the diet. This is notable given that nutrient deficiencies can sometimes occur in SIBO at baseline. 
• We would be most likely to first treat with a more validated approach while also monitoring for and correcting underlying nutrient deficiencies. We personally would use diet as a symptom management aid after these initial steps, and would not present diet as a treatment. 
• We disliked how antimicrobials were built into the program at a time when the diet is supposed to become more lenient. We feel this might lead some to misconstrue common side effects of antimicrobials as food intolerance after adding back more foods. 
• We feel the diet lacks a targeted means to assess for food intolerances and sensitivities. 
• In the end, the Bi-phasic diet adds more structure but remains highly restrictive. In phase 2, the diet continues to limit several health-promoting foods with no clear time parameters for reintroduction and testing. We find this concerning and cannot advocate this approach because there are too many unknowns. There is simply a lack of supporting evidence for this approach and we believe risks of malnutrition or microbiome scarring might be considerable.