5 SIBO Diets Compared - SCD vs Biphasic vs Cedars Sinai & 2 More
Which SIBO diet is best for you? Well, in this epic guide we compare the top 5 SIBO diets, so you can see how they differ and which might work best for your gut.
Table of Contents
1. Specific Carbohydrate Diet
Dr. Sydney Haas
The Specific Carbohydrate diet was created by Sydney Haas, MD and popularized by Elaine Gottschall’s book, ‘Breaking the Vicious Cycle.’ The book describes what the SCD is, how to implement it, and claims its benefit as a treatment for a variety of GI disease states.
In The Vicious Cycle she compares the mechanism of action of the SCD to the elemental diet. However elemental formula is based on broken down (or pre-digested) proteins and not carbohydrate content.
Vivonex® Plus Essential and Peptamen®, both elemental formulas, have maltodextrin and cornstarch listed as ingredients which are not monosaccharides, contradicting what would be ‘legal’ on the SCD (Diet as a therapeutic option for adult IBD).
The SCD is broken down into ‘legal foods and ‘illegal’ foods. She advocates for ‘fanatical adherence’ to the diet for at least 1 year after the last symptom or flare-up. During the reintroduction phase, she suggests trying one ‘illegal’ food per week. However, if a symptom reoccurs, you are to return to only eating foods from the ‘legal’ food list, and does not specify when to restart the reintroduction of foods again.
Legal foods include unprocessed meats, most fresh vegetables and fruits, all fats and oils, aged cheeses and a home-made lactose-free yogurt.
Illegal foods include milk and most milk products, grains, soft cheeses, beans/legumes, and non-honey sweeteners. Illegal foods are labeled as such due to their chemical structure.
The premise of the diet is that foods containing specific types of carbohydrates, disaccharides or polysaccharides, are more difficult to digest, resulting in undigested carbohydrates arriving in the colon and causing fermentation, overgrowth of bacteria and yeast (shifting toward a more pro-inflammatory microbiome profile), and subsequent intestinal injury and inflammation.
‘Legal’ foods are any type of food that do not ferment in the colon or are easily absorbed; therefore, not causing bacterial growth or trigger GI distress. You can access the entire legal/illegal food list online (link below).
Gottschall states in her book, The Vicious Cycle
“The diet is based on the principle that specifically selected carbohydrates, requiring minimal digestive processes are absorbed and leave virtually none to be used for furthering microbial growth in the intestine.”
Similar to other dietary strategies for SIBO, the goal is to eliminate carbohydrates from the diet that can be fermented in the intestines.
“The purpose of the SCD is to deprive the microbial world of the intestine of the food it needs to overpopulate. By using a diet which contains predominantly predigested carbohydrates, the individual with an intestinal problem can be maximally nourished without overstimulation of the intestinal microbial population.”
Summary of Available Research
There have not been studies with the Specific Carbohydrate Diet and SIBO, explicitly. There have been studies with the SCD and IBD. The studies conducted are generally a small sample size of children with IBD. Some studies have shown improvement on inflammatory markers, mucosal healing, and symptoms, data continues to be limited, especially for the adult population (Popular Diet Trends for IBD).
In a survey of 50 subjects affected by IBD and self-treating with the SCD, the clinical remission was observed in 66% of patients after about 10 months following the nutritional regimen.
Furthermore, numerous subjects were able to discontinue corticosteroid therapy . The authors specifically indicate changes in intestinal microbiome they previously observed as a contributory mechanism explaining the positive results they observed .
An anonymous online survey completed by 417 adult patients suffering of IBD (47% CD, 43% UC, and 10% indeterminate colitis) and following the SCD, showed that 33% and 42% of patients experienced symptomatic remission after 2 and 6–12 months of diet, respectively . Among the outcomes self-assessed by patients, abdominal pain was improved as well as improvements regarding diarrhea, blood in the stool, limitations of activities and weight loss.
Of note, concerning the impact of SCD on the microbiota and microbiome, twelve pediatric patients aged 10 to 17 with mild to moderate IBD and subjected to SCD diet for 12 weeks underwent significant clinical improvement; the authors observed a distinctive dysbiosis for each individual in most pre-diet microbiomes ending in significant changes in microbiota composition after dietary switch. Interestingly, changes were not consistent in all patients (with contrasting results regarding even microbial diversity, where some patients showed increasing post-diet diversity, others showed a decrease) .
A case report of a young lady with a UC diagnosis and assuming SCD, showed that the diet successfully improved all UC symptoms and induced a dramatic variation of the microbiome. Prior to the SCD regimen, the most abundant species were Fusobacterium ulcerans and Viellonella dispar.
In that study, the microbiota of the case subject was compared to that obtained from three healthy subjects with no restriction diet. None of the species Fusobacterium ulcerans and Viellonella dispar were found in the control subjects, where instead the dominating species were Bacteriodeaceae, Ruminococcaceae and Lachnospiraceae. After two weeks of diet, the patient’s microbiome showed a decrease of Fusobacterium ulcerans alongside a marked increase of many Enterobacteriaceae species .
In another trial, six subjects with CD compared to two healthy controls, were treated with SCD or low residue diet for thirty days. Fecal samples were evaluated at day 1 and day 30. At baseline, the results, consistent with previous findings, showed a reduced microbial diversity in CD patients. The most increased classes were Clostridia and Gammaproteobacteria and some species of the Phylum Bacteriodetes, while Clostridium lactifermentans was reduced. After the SCD regimen, the microbial diversity increased with a high prevalence of nonpathogenic species of the clostridia family. However, no clinical significant improvement was observed . On the whole, robust data—especially on adults—are lacking, and prospective investigations, possibly through comparative case-control studies, are warranted to get an in-depth understanding of how the SCD may impact the microbiota and the microbiome .
(Nutrition, IBD and Gut Microbiota: A Review)
Several studies have been published that suggest that SCD may be effective in IBD and most clinical observations have been in pediatric disease. These are reviewed in a separate chapter on diet and pediatric IBD. In adults, our group demonstrated that the fecal microbiome of IBD patients following the SCD may be different and more biodiverse than IBD patients following a Western diet based on 16 srRNA analysis of fecal microbiota composition [125, 126]. We also published a case series of fifty IBD patients on the SCD and showed that SCD-followers had decreased symptom scores and a high quality of life .
The majority of these patients had colonic CD and some were able to maintain clinical remission using diet without maintenance medications. There is also evidence that following the diet is associated with improvements in ESR, CRP, calprotectin and Lewis score on capsule endoscopy; nevertheless, concomitant medication use in some of these patients is a potential confounder [128–130]. Results of an online survey of IBD patients following the SCD hints at the possibility of the diet helping to prevent IBD complications and hospitalizations though this is only patient reported and needs further study prospectively .
Though Gottschall recommends strict adherence to SCD, there is some data to suggest some liberalization may be possible with continued maintenance of remission , and patients in our published case series and in our clinical observations have tolerated and done well with some of the “illegal” food items on an individual basis. This suggests that SCD is a starting point for IBD patients to explore their individual diet-disease relationship especially in the maintenance phase; and that patients could potentially conduct trial and error experiments on themselves with the aid of a health provider who can give objective dietary and clinical advice and can follow how they respond with preferably with objective assessments.
Unfortunately, the appropriate time from diet initiation to liberalization is not clearly defined. Gottschall only recommends staying on the SCD for at least 1 year after the last symptom has disappeared but there are no formal recommendations regarding how to (Diet as a therapeutic option for adult IBD)
Gottschall claims that this diet can aid in the healing of ulcerative colitis, Crohn’s disease, cystic fibrosis, Celiac’s disease, and autism (Vicious Cycle); however, evidence is lacking. There does seem to be promise of symptom relief with crohn’s disease and ulcerative colitis. Some studies have shown improvement on inflammatory markers, mucosal healing, and symptoms, data continues to be limited, especially for the adult population *(Popular diet trends for IBD)*.
We suggest that any restrictive diet should be overseen by a Registered Dietitian to ensure nutritional adequacy, with plans for the reintroduction of foods to promote diversity in food intake, while maintaining symptom control.
2. Biphasic Diet
Nirala Jacobi, ND
The Bi-Phasic Diet is a more structured approach to the SSFG. The SSFG’s guidelines are broad and vague, so the Bi-phasic diet was created to give better, more specific, instruction. The diet is carried out in two phases. The theory is that this ‘2-phase’ approach helps to limit the side effects of bacterial and fungal “die-off,” while helping to eliminate bacterial overgrowth from the small intestine. Phase 1 is labeled as ‘reduce and repair.’
The first phase is broken down into two categories: ‘restricted’ and ‘restricted.’ Dr. Jacobi recommends that those who start on the diet begin with the foods on the restricted column and move to foods on the ‘semi-restricted’ column once symptoms start to subside. This first phase is said to reduce and repair inflammation, and lasts for 4-6 weeks.
Phase 2, which is labeled, ‘remove and restore,’ becomes slightly less restrictive and also lasts for 4-6 weeks. The ‘remove’ refers to removing bacteria and, and ‘restore’ refers to restoring motility.
The claim is that this diet is intended to help manage and recover from SIBO faster, and to have immediate symptom relief and ‘clear SIBO for good.’
Summary of Available Research
Like the SSFG diet, there is no research stating the efficacy of this approach. There are studies that have been done on both the low FODMAP and SCD that are summarized in their sections above.
Like the SSFG, the diet may be more restrictive than necessary. Dr. Jacobi does recommend expanding your diet as quickly as your body can tolerate.
3. Cedars Sinai Diet / Low Fermentation Diet
Dr. Pimentel’s version of a SIBO diet is the most liberalized of the diet therapies used to relieve SIBO symptoms. He implements diets in his patients after antibiotic treatment as a way of preventing bacterial overgrowth to reoccur. The diet focuses on eliminating foods that are easy to digest, and to avoid non-digestible carbohydrates. Along with the outlined dietary restrictions, he advises to allow 4-5 hour spacing between meals.
He encourages this to allow the GI system to ‘clean’ itself. He puts it like this: the gut has a cleaning mode and a digesting mode. When you are not eating, your food is not able to ‘clean’ itself from the foods you’ve eaten. If you are constantly eating, there is no time to clean, so food is staying in the gut and bacteria is feeding off it, perpetuating bacterial overgrowth.
To better understand his diet, we reviewed the available PDF online for the ‘Low Fermentation Diet’ and Pimentel’s book, “A New IBS Solution.”
Dr. Pimentel’s book gives 10 major guidelines for managing symptoms with diet.
- Avoid corn syrup (fructose), mannitol, sorbitol, sucralose, lactose, lactulose
- Limit ‘high residue’ foods like beans, lentils, peas, soy products, yogurt
- Keep hydrated with water, 8 cups a day
- Beef, fish, poultry, and eggs are good sources of protein and don’t need to be limited other than appropriate portions for your ‘body size.’
- Eating ½ cup to 1 cup of carbs at a meal, which includes potatoes, pasta, rice, bread, and cereals. White bread, rice, etc are better than the whole grain version
- Limit fruits to 2 servings/day. Do not eat dried fruits because this concentrates the amount of fructose per serving
- Eat vegetables daily. Cooked is easier to digest than raw. If you eat a salad, make it small.
- Avoid dairy products and soy-alternatives. Rice milk or Lactaid milk are appropriate alternatives
- Coffee, tea, and soda should be consumed in moderation, with tea being the best option. Avoid any beverage made with corn syrup or non-nutritive sweeteners like sucralose.
- Make sure you eat sufficient calories to maintain body weight with moderate exercise.
The guidelines available online have additional specifics within plant food groups. For vegetables, he advises, ‘no beans, legumes, cabbage, brussels sprouts, broccoli, cauliflower, or green leafy vegetables, but side salads are okay,’ and definitely no hummus due to the chickpea content. Meanwhile, ‘anything that grows under the ground or off a plant is okay.’
This includes onions, garlic, potatoes, yams, beets, carrots, turnips, peppers, tomatoes, cucumber, zucchini, squash, eggplant, peas (not the pod). He specifically mentions all mushrooms are okay to eat. For fruits, he advises against eating apples, pears, and bananas because they ‘are constipating.’ All nuts are okay to eat on this diet.
In his book, he gives a 5 day meal plan to help his readers get the gist of what they can eat. However, we put the meal plan
Diet is meant to prevent bacterial overgrowth recurrence by limiting fermentable foods in the diet.
Summary of Available Research
There is currently no research on this specific diet. In one of Pimentel’s latest review articles on SIBO, he states that the dominant theme in diet manipulation for SIBO is the reduction of fermentable products, a low fiber diet, and avoidance of alcohol sugars and other fermentable sweeteners such as sucralose. His diet appears to be built off these concepts (ACG Clinical Guidelines: SIBO).
While Dr. Pimentel is leading the research in SIBO, we do have some questions regarding how he established these parameters for this diet. For example, some of the foods he allows are high FODMAP. The diet allows all nuts when cashews, pistachios, and almonds are high FODMAP. The allowance of mushrooms, onion, and garlic was most surprising to us considering that Monash does not have a ‘green light’ portion size for these foods, suggesting that they are highly fermentable. The claim that apples, pears, and bananas are constipating was also strange to us considering apples and pears are high in sorbitol and would be more likely to cause diarrhea than constipation. So apples and pears probably should be avoided due to sorbitol content (high FODMAP), but not due to their potential for constipation. As for bananas, they are allowed on a low FODMAP, the SSFG, and Bi-phasic diet, and while green/unripe bananas may add bulk to stool (SOURCE), there is no research showing they are constipating. From listening to him speak on various podcasts, it is our understanding that he created these guidelines to have an easier approach for people. Overall, this diet approach is nice because of how simple the guidelines are. However, we would caution eating some of those ‘red light’ High FODMAP foods like mushrooms, onion, and garlic.
4. SIBO Specific Food Guide (SSFG Diet)
Allison Siebecker, ND
The SSFG (PDF) was created to encompass the concepts and guidelines from the low FODMAP and Specific Carbohydrate Diet. It reduces a broad range of fermentable carbohydrates. Next to the elemental diet, it is the most restrictive of the therapeutic diets for SIBO.
Dr. Siebecker gives some guidelines to her diet on the diet food list. When beginning the diet, Dr. Siebecker suggests starting the SCD along with low and moderate FODMAP-containing foods, but limiting moderate FODMAPS to 1 serving per meal. Reintroduction of certain foods can start after 1-3 months.
No instructions were given on what would indicate starting reintroduction after 1 month or after 3 months; although, we assume it's if there is symptom control. She recommends to cook, peel, de-seed, and puree fruits and vegetables when first trying--we’re not sure if this means at the start of the diet or with reintroduction or both. She also recommends meal spacing of 3-4 hours between meals and monitoring portion sizes (given on her handout).
She advises to avoid dairy at the beginning of reintroduction if you’re unsure of tolerability. She emphasizes the importance of individuality and to trust symptoms or relief from symptoms over the list, and to periodically reintroduce foods that were previously
Dr. Seibecker says that she ‘takes the best of both’ from the Low FODMAP diet and SCD in order to reduce a ‘broader range of fermentable carbohydrates’ than any other SIBO diet. The diet is tweaked to include restrictions based off of her own clinical experience with treating SIBO as well. Like with the Low FODMAP diet and SCD, the goal is to decrease the amount of fermentable carbohydrates with the intention to ‘starve’ the gut bacteria.
Summary of Available Research
Currently there is no evidence on the SSFG, specifically. Research exists for both the Low FODMAP diet and the SCD; however, neither diet has been researched in their potential treatment of SIBO.
The SSFG may be unnecessarily restrictive. Dr. Seibecker encourages people to try less restricted diets before trying the SSFG due to how restrictive the diet is.
5. Low FODMAP Diet
The Low FODMAP diet was created by Monash University and has shown to be beneficial in IBS sufferers. The diet's goal is to maintain IBS symptom control while trying to expand food options as much as possible. While the diet was not meant to treat SIBO symptoms initially, it is thought that up to 78% of people with IBS also have SIBO.
Although the rate of SIBO in IBS is debated, there is little controversy that some people with IBS have SIBO (ACG Clinical Guidelines: SIBO).
The term ‘FODMAP’ is an acronym that stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols.1 These are names for several groups of small carbohydrates -- made up of 1 to 10 sugars -- which are indigestible or not absorbed well in the gut.2 A low FODMAP diet is a 3-phased plan which restricts (phase 1), challenges (phase 2), and then reintroduces FODMAPs found in several common foods (phase 3).
The foods that are restricted include certain fruits, vegetables, legumes, grains, honey, sweeteners, milk, and certain dairy products.2 When following the low FODMAP diet, whether it is for IBS or SIBO, it is suggested to stop the diet if there is no symptom relief with food restriction in phase 1. The restriction phase of the low FODMAP diet (phase 1), where all FODMAP-containing foods are eliminated, is only followed for 2-6 weeks.
Food challenges in phase 2 of the diet last for 6-8 weeks. Permanent elimination is not the goal. A balance between symptom management and a broad and diversified diet is the end goal. Many FODMAPs come from very healthy foods. Even FODMAPs themselves may act as prebiotics or “food” that helps to feed our good gut bacteria.
However, these carbohydrates can still be poorly tolerated and lead to uncomfortable symptoms in sensitive individuals. Gluten itself is not avoided in the low FODMAP diet as it is a protein, whereas FODMAPs are carbohydrates. Many gluten-free foods are eaten or recommended on the diet, not because of the gluten content, but because of the higher FODMAP content in many gluten-containing foods.
Some gluten-containing foods such as sourdough spelt bread are low in FODMAPs and can be eaten on the diet.3 Below are examples of FODMAP-containing foods. Remember, the low FODMAP diet's goal is to eventually add in as many healthful FODMAP containing foods as possible while still maintaining control over IBS symptoms.
Examples of FODMAPs and their primary sources:
Oligosaccharides (GOS*, Fructans)
Found predominantly in legumes/beans/pulses, wheat, rye, onions, and garlic
Found in dairy products such as milk, soft cheese, and yogurts
Monosaccharides (excess Fructose)
Found predominantly in foods such as honey, apples, pear, mango, fig, and high fructose corn syrup
Polyols (e.g., sorbitol and mannitol)
Found in some fruits and vegetables and added to diet products (e.g., hard candies, gum, soft drinks)
It is thought that the low FODMAP diet may improve SIBO symptoms by reducing intake of highly fermentable, short-chain carbohydrates (FODMAPs). This in turn reduces the ability for bacterial fermentation. The reduction in bacterial fermentation is what is thought to reduce symptoms like gas, bloating and abdominal pain (Monash mod 10). It is important to note that FODMAPs are not allergens; allergens cause symptoms by causing an immune response. Whereas FODMAPs are causing discomfort due to how they impact the “plumbing” of the bowels in sensitive individuals.
Summary of Available Research
Unfortunately, difficulties in the measurement of SIBO make it near impossible to assess the efficacy of treatments for SIBO via intervention studies.
A number of diets are commonly used to treat SIBO, including the low FODMAP diet. However, no studies are available to confirm the efficacy of diet treatment in SIBO. For those who want to trial a low FODMAP diet to treat SIBO symptoms, we advise this is done with the help and oversight of a Registered Dietitian.
The dietitian can assist each phase of the diet to ensure things like nutritional deficiency is avoided and food diversity is achieved.
The success of the diet should be concluded by the relief of symptoms and not by breath test results, as breath test results have shown to have a high rate of false positives in diagnosing SIBO. (Monash module 10)
An evidence hierarchy is followed to ensure conclusions are formed off of the most up-to-date and well-designed studies available. We aim to reference studies conducted within the past five years when possible.
- Systematic review or meta-analysis of randomized controlled trials
- Randomized controlled trials
- Controlled trials without randomization
- Case-control (retrospective) and cohort (prospective) studies
- A systematic review of descriptive, qualitative, or mixed-method studies
- A single descriptive, qualitative, or mixed-method study
- Studies without controls, case reports, and case series
- Animal research
- In vitro research