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Since my first article on resistant starch (RS) titled Resistant Starch – Friend or Foe?, raw unmodified potato starch, or RUMPS as I like to call it, continues to light up the blogosphere. Like a lot of people, I was caught off guard by the overwhelmingly positive light RUMPS has been cast in. Some people have truly fallen in love with this molecule, or rather two molecules (amylose and amylopectin) all tangled up together.  Even Tom Naughton and Mark Sisson have fallen and Jimmy Moore wants to get some. The explosive interest in this topic can be traced to the extraordinary efforts of two flies in the nutritional ointment, Tim Steel, AKA Tatertot and Richard Nikoley of FreeTheAnimal.com.

The reported benefits of RUMPS include the enticing claims of better sleep and vivid dreams. Those alone make me want to buy some tonight and give it a try, but there’s more: improved gut function, curing Small Intestinal Bacterial Overgrowth, SIBO (Say what?) preferentially feeding healthy gut bacteria, preventing cancer with more butyrate, immune stimulation, toxin/carcinogen degradation, blood sugar/insulin control, improved cholesterol, triglycerides and even weight-loss.

Most of the claims about RUMPS are unproven, though some are surely real. Some research already supports RS’s effect on blunting postprandial blood sugar spikes, suggesting that RUMPS may be a powerful tool for diabetics and others who suffer from hyperglycemia. But what really caught my attention was the claim that RUMPS will “Cure” SIBO. After all, RUMPS is a form of resistant starch, which I have recommended limiting for SIBO. For more info on this counterintuitive idea, you can visit Dr. BG, AKA Grace, at Animal Pharm and Dr. Art Ayres at Cooling Inflammation. You can also see my mini-debate with Tim in the comments section on Dr. Mike Eades’ blog on heartburn.

Since this idea has been put forward, several people, including some who have experienced side effects with RUMPS, have asked for my opinion on using RUMPS if they have SIBO. Recall my concluding opinion from my first article:

“A state of fermentable substrate limitation in the gut is healthier than a state of fermentable substrate excess and more consistent with Paleo diet concepts (based on limited availability of food, regular fasting while foraging, eating seasonal fruits, etc.). A lean diet for our gut microbes fosters healthy competition in the gut that will favor the survival of well adapted organisms best suited to be our partners in digestion and health. We know that excess malabsorbed carbohydrates (lactose and fructose intolerance for instance) are linked to conditions associated with SIBO (small intestinal bacterial overgrowth) and there is reason to believe that resistant starch may contribute to imbalances in the gut microbiota including SIBO in susceptible people.”

Since writing this, I have learned a bit more about RUMPS specifically (as opposed to RS in general). I will do my best to provide some thoughts on using RUMPS for SIBO in more or less a pros and cons format. As always, please do add your comments on any points or evidence I may have missed for, or against this approach.

Could RUMPS actually help people with SIBO?

Tim and Richard contacted me recently to discuss some of the experiences people were reporting after supplementing with RUMPS. At that time, we agreed to share all information, both positive and negative about RUMPS and digestive health issues going forward. Realizing that our real goal was to help people and that science will figure this out eventually anyway, we agreed to do our best to speed things up hopefully benefiting all involved. In other words:

“Instead of making science conform to our beliefs, let’s find out what’s real and update our understanding”

And wouldn’t you know it, shortly after making this agreement, I was contacted by someone who had been on antibiotics, had confirmed SIBO and IBS symptoms for years. She had been taking probiotics, eating fermented foods and adding RUMPS to her diet. Other than some bloating and flatulence, she reported feeling better and able to eat a more varied diet without repercussions.

Even though this particular report involves one person who had previously eliminated her symptoms on the Fast Tract Diet (that limits not only RS, but several other fermentable carbs as well), a few other people have also reported improvement in heartburn or other SIBO-related symptoms using RUMPS. To me this suggests there is at least a chance that RUMPS could benefit some people with SIBO. I am open to the idea. Hey, at least we’re talking about diet these days, not PPIs, H2 blockers, gut wrecking antibiotics and some absolutely frightening IBS drugs.

RUMPS is like a “bus” for bacteria:

Pros: One idea proposed to explain why RUMPS might cure SIBO, is that any bacteria overgrowing in the small intestine will adhere to the RUMPS molecules and be whisked back into the large intestine, from whence they came. This is an interesting idea which has some support from a study showing that people infected with Vibrio cholera suffer less fluid loss and recover more quickly when RS is added to the rehydration solution[1]. Supporting this idea is the finding that, under the right conditions, V. cholera can rapidly and efficiently adhere to starch molecules.[2]

Cons/Questions: Some questions remain to determine if these results support using RUMPS with SIBO:

  • While bacterial adherence to corn starch was very efficient (98%), adherence to other starch types did not fare as well with very little adherence to wheat starch and no significant adherence to instant potato starch – which admittedly is quite different from RUMPS. RUMPS was not tested for bacterial adherence.
  • The adherence testing for the publication was done in the laboratory. No one knows if similar adherence would occur in people’s intestines, though the results agree with the observations in treating Cholera with RS.
  • Several other types of bacteria including: L. monocytogenes, S. typhimurium, P. aeruginosa, E. coli, and A. hydrophila, absorbed to the starch much less efficiently (1 – 57% vs. 98% with Cholera). According to the authors, V. cholera can utilize starch for growth while the other bacteria don’t, potentially explaining a purpose behind V. cholera’s ability.
  • Sugars utilized by V. cholera including: glucose, maltose, sucrose, trehalose, dextrins, and fructose, blocked adhesion in the lab and could potentially affect binding in vivo (in the small intestine) as well.
  • Cholera-induced infectious diarrhea is a dramatic and acute condition caused by a specific pathogen which is quite different from diarrhea-predominant IBS, constipation-predominant or mixed IBS as well as other SIBO-related conditions that involve many different types of bacteria.

Can other resistant starches or fibers accomplish the same thing?

Pros: Another report showed that green banana or pectin fiber improved recovery times of children with diarrhea.[3] In this case, most of children had no specific infectious agent identified, while 40% were diagnosed with either rotavirus (17%), E. coli (11%), V. cholera (5%), or Salmonella (4%).

Cons/questions: The actual amount of resistant starch from green banana is unclear in this study as it was cooked. Also the control diet was rice, but the type or rice and its contribution to the total amount of RS was not determined. Also, in this study, diarrhea had a variety of causes including acute viral and bacterial infections.

Can RUMPS be fermented in the small intestine?

As a rule of thumb, the most rapidly fermentable carbohydrates, if poorly absorbed, have the highest chance of being fermented by bacteria in the small intestine (the home of SIBO for those that have it), where the capacity for excessive fermentation is most limited, and damage most likely to occur. Fructose (grrrrr) and lactose (grrrrr) are good examples of carbs fermented in the small intestine, so it’s no big surprise that they are so well known in the scientific literature as GI trouble makers. But more fermentable forms of fiber such as fructans, pectin, beta glucan and gums are relatively easy to ferment as well. At the other extreme are cellulose, methyl cellulose and lignin that are less fermentable and less of a SIBO threat. Fibers from legumes including stachyose, raffinose and verbascose fall somewhere in the middle along with sugar alcohols.

As with fiber, some forms or RS may be more fermentable than others, with the degree of gelatinization being a factor as well. RUMPS is one type of resistant starch referred to as RS2. You can find a definition of all RS types in my first article. Like the many types of fiber, the various forms of RS have different properties and are fermented at varying rates by different combinations of bacterial species (each species of bacteria have specific abilities in terms of fermenting carbs and often need to work together to get the job done finally consuming the breakdown product (glucose)). Where RUMPS falls in this fermentability continuum is at the heart of the issue in my opinion, and something I admittedly have recently been learning more about

Pros: A study by Olesen, et. al.[4] (thanks for the paper Tim) found that 50 grams of RUMPS (29 g RS), though fermentable, was less fermentable than 10 g of lactulose. Similar results were found in a second study.[5] Lower fermentability translates into fewer symptoms. Lactulose for example, is not digested or absorbed by humans but is highly fermentable by gut bacteria and can cause dramatic GI symptoms including flatulence, bloating, diarrhea, stomach pain, nausea and vomiting. (http://drugs.webmd.boots.com/drugs/drug-259-Lactulose.aspx).

In the Fast Tract Digestion books, I estimate the relative fermentability of fiber types. Perhaps RUMPS should be reclassified as a fiber and belongs on the lower end of that list, say above cellulose but below pectin, raffinose, stachyose and verbascose and may be less symptom provoking than more fermentable carbs.

Cons/questions: Though I don’t know the glycemic index of RUMPS specifically, the GI of another type II resistant starch, Hylon VII corn starch is 50, indicating that half of the starch is broken down and absorbed in the small intestine.[6] If human starch degrading enzymes are able to breakdown resistant starch, why wouldn’t bacteria that possess starch-degrading enzymes, known to be present in SIBO, do the same. Of course the question here is how different is RUMPS from Hylon VII.


It’s tempting to assume that if RUMPS is not fermented in the small intestine, it won’t trigger any SIBO-like symptoms. But there is the question of excessive fermentation in the large intestine. Before SIBO, excessive bacterial fermentation was referred to as dysbiosis, or a general imbalance or overgrowth of intestinal microbiota believed to be associated with bowel inflammation. Though not typically specified, dysbiosis can include bacterial overgrowth growth in the large intestine. You could think of this as LIBO for Large Intestinal Bacterial Overgrowth. Is it possible LIBO could also contribute to symptoms more commonly attributed to SIBO? Since our large intestine is designed to support more extensive fermentation, it’s easy to assume “the more fermentation the better” as long as it’s in the large intestine, but I am not so sure. Since SIBO is associated with bacteria originating from the large intestine, is it possible that LIBO can give rise to SIBO?

Years ago, I suffered chronically with acid reflux (before reducing fermentable carbs in my own diet). I often noticed occasional bouts of acid reflux some 12-24 hours after consuming foods with a high fermentation potential (hard to digest carbs). Though research on this phenomenon is lacking, I wonder if excessive fermentation in the large intestine could contribute to acid reflux, IBS and other symptoms more commonly associated with SIBO. If this were the case, even slower to metabolize fibers and RS could trigger symptoms.

Pros: The idea that RUMPS could cause symptoms via LIBO is speculative.

Cons: If correct, RUMPS could trigger symptoms via excessive fermentation in the large intestine

RUMPS GI Side Effects

I still remember the parties we had in high school. Get a hold of some beer. Invite your friends and their friends over and put on some Jimmy Hendrix (yes, it was the 70s). Early on everyone is focused on the fun and excitement, but then you realize its 2:00 AM, Bobby dropped some acid and is typing something on your mom’s typewriter, the foreign exchange student is vomiting in the bedroom and your sister’s boyfriend just tore up the front lawn with his Camaro and is now stuck dangling over the embankment (true story). At some point, common sense kicks in and it’s time to wind the party down a notch and take stock.

I think this is what’s happening with RUMPS. It’s tempting to throw caution to the wind when you’re chasing amazing health claims. But I have been surprised to see many comments from people suffering with side effects of RUMPS who continue to use the supplement, even upping the dosage in some cases. Before we resume the RUMPS party, let’s take a look at people reporting side effects on RUMPS.

In my first post on RS, I discussed the “bread and muffin study” showing that these RS-containing foods invoked more symptoms in people with IBS, I noted that 80 % of cystic fibrosis patients, who are often deficient for the release of starch degrading amylase enzyme and test positive for SIBO, suffer from acid reflux (Refer to Fast Tract Digestion Heartburn for the evidence tying acid reflux to SIBO). I also talked about the similarity between the symptoms of SIBO and the side effects of drugs and supplements that block starch digestion.

Consistent with these observations, reports of GI side effects from RS (not RUMPS specifically) include: flatulence, bloating, stomach aches, cramps and diarrhea.[7],[8] Though both studies were conducted in healthy people, the reported side effects are consistent with SIBO or a general imbalance of gut microbes – dysbiosis. I would expect the side effects to be worse, not better, in people who already had established SIBO or dysbiosis.

While most people supplementing with RUMPS report varying amounts of flatulence, some report additional side effects including: abdominal pain, diarrhea, constipation, gas, bloating, acid reflux, nausea, cramps fatigue, and even intestinal blockage. These reports come from the comment sections under the many RUMPS blogs. Keep in mind they are anecdotal (n=1) reports so we shouldn’t read too much into them, but we also can’t ignore them.

These reports of side effects mirror my own experiences over the years with RS in general. Though I don’t supplement with RUMPS, I suffer from acid reflux when I consume pasta or certain rices and breads with high levels of RS. My gut can tell the difference between basmati rice (high RS) and jasmine rice (no RS) with a fairly high degree of certainty.

Tim Steele recounted to me his own experience when he consumed additional RUMPS in response to a bout of indigestion. These are his words: “I felt some indigestion coming on, and took 4TBS of RUMPS in a glass of water. Almost instantly, the heartburn was unbearable, nearly doubled me over. I ate at least 6 TUMS and got a bit of relief, but the discomfort actually lasted all night and into the next day.”

Richard Nikoley also recounted to me a report of someone having to stop supplementing with RUMPS: “because after a while it gave him perpetual heartburn for days.”

A post from Mark’s Daily Apple recently stated: “A note for those experiencing heartburn from the PS, it has taken over a week off the PS to get the HB under control.”

A post on Facebook, though not specifically about RUMPS, noted: “Several of us in The Paleo Approach Group have problems digesting plantains. I had issues for over a week, severe stomach pain and psychological issues, worse than anything I’ve eaten in a long time. I’m thinking it has to do with the large amount of resistant starch feeding bad bacteria.”

RUMPS AI Side Effects

Others have complained that RUMPS exacerbated their preexisting autoimmune conditions such as rheumatoid arthritis (RA) and ankylosing spondylitis (AS). Symptoms included joint pain in the hip, knee, extremities and back. Despite the side effects, some people continue to supplement hoping to gain benefit even though their own bodies are telling them to stop. Before assuming that RUMPS is the appropriate course of action for AI conditions, a thorough review (beyond this article) of bacterial involvement in specific AI conditions is in order. For instance:

  • K. pneumonia (capable or degrading RS) overgrowth and antibodies to the same have been linked to AS and possibly Crohn’s disease, and dietary starch restriction has been proposed as a treatment strategy[9].
  • RA has been linked to increased intestinal populations of Prevotella copri and a decrease in Bacteroides strains,[10] Yet Prevotella is associated with carbohydrate-based diets while Bacteroides is associated with animal-based diets.[11]

Note: RA has also been linked to urinary tract infections caused by the bacterium Proteus mirabilis.[12] How these two very different bacterial strains, one growing in the gut (Prevotella. copri) and one causing UTI infections (Proteus mirabilis), contribute to RA has yet to be determined.

Given the complexity of AI and SIBO-related conditions, can we assume (as has been commonly stated) that people with these conditions will always benefit by improving their “good” and reducing their “bad” gut microbes with RUMPS? In reality this strategy has not been proven and does not seem to be working, at least for some people who may be ignoring the risks in pursuit of perceived benefit. I remain open, but continue to believe that RUMPS has the potential to invoke symptoms in people who have SIBO or are susceptible to SIBO or dysbiosis, particularly if they consume higher doses.

The connection between gut microbiota, SIBO and diet

We know that our gut microbiota can be significantly influenced by diet and disease. But understanding what this means will take some time. Studies show that people with IBS (IBS is definitively linked to SIBO) have increases in Firmicutes type bacteria Dorea, Ruminococcus, and Clostridium spp., and decreases in Bacteroidetes, Actinobacteria (Bifidobacterium), and one specific Firmicutes –Faecalibacterium spp.[13],[14] A study by Malinen and colleagues,[15] found that a predominance of Ruminococcus type bacteria (related to R. torques) was associated with severity of bowel symptoms in IBS subjects. However, within this high group, several species of Clostridia were significantly reduced. A study looking at microbiota changes in IBSD and IBSC found that R. torques was more prevalent in IBS-D and R. bromii (recall the “keystone species” in RS fermentation) was associated with IBS-C patients in comparison to control subjects.[16] Another study showed that the microbiota in IBS-D patients was enriched in Proteobacteria and Firmicutes (particularly Lachnospiraceae and sometimes R. torques), but reduced in Actinobacteria and Bacteroidetes compared to controls.[17]

 Table 1. Microbiota characteristics and population changes in IBS

Microbiota typeRelative change in IBSGas producingStarch degrading



  • Ruminococcus



  • R. torques



  • R. bromii



  • Rosburia



  • E. rectale
No change



  • Clostridium spp.[18]
Increased or decreased



  • Dorea (Clostrid.)



  • Lachnospiraceae (Clostrid.)



  • Faecalibacterium spp.


ProteobacteriaNo change or increased


Actinobacteria (bifidobacterium)[13]Decreased






While there are many contributing factors for SIBO and IBS covered in Fast Tract Digestion IBS that may alter microbiota composition, and different studies yielded some variability in results, the microbiota profiles of people with IBS show an important trend. Two things struck me immediately after putting the data into a table:

  • IBS involves increases in many Firmicutes type bacteria, which are most adept at degrading polysaccharides such as resistant starch, and a decrease in more nutritionally versatile Bacteroidetes and certain Clostridia. Actinobacteria were also lower in IBS.
  • The Firmicutes type bacteria that are increased, are most proficient at producing (mostly hydrogen and carbon dioxide) gas.

The connection between IBS and increases in bacterial species that preferentially ferment complex carbs and produce gas is consistent with the success of diets that limit fermentable carbs for IBS, acid reflux and other SIBO related conditions – covered in my first article.

Irritable Bowle Syndron (IBS) and Obesity

The microbiota profile of people with IBS is consistent with a diet rich in fermentable carbs. The same is true for obese individuals, which may explain the connection between obesity and GI symptoms including bloating, diarrhea, and an even stronger connection with acid reflux.[22],[23]

In a study of overweight men, a diet supplemented with RS yielded significant increases in Ruminococcaeae, Roseburia and E. rectale, which decreased significantly when subjects were switched to a lower carb weight-loss diet.[24]  Similar results were obtained in study on the effects of reducing dietary carbohydrates (high carb 399g/day, moderate carb 164g/day, low carb 24g/day) on microbiota in obese men.[25]  As dietary carbs were lowered, the researchers observed a decrease in Roseburia and E. rectale related (clostridial cluster XIVa) species as well as bifidobacteria (Actinobacteria). Bacteriodes group and Clostridium coccoides group bacteria as well as clostridial cluster IX group bacteria were not significantly affected by reducing dietary carbs.

In general, obesity is associated with a significant decrease in microbiota diversity with fewer Bacteroidetes (associated with more diversity) and more Firmicutes and Actinobacteria (associated with less diversity).[26] The authors found that the obese human gut microbiome (microbiome refers to gut microbe genes, whereas microbiota refers to the actual bacteria) is genetically enriched for phosphotransferase systems involved in microbial processing of carbohydrates. They likened the obese gut microbiota more to fertilizer runoff, where abnormal energy input creates blooms of less diverse microorganisms, compared to a lean gut microbiota that is actually more like a rain forest. These findings are in agreement with other microbiota studies on obesity.[27],[28],[29],[30]  The reason may have to do with the ability of Bacteroidetes type bacteria, as well as some Clostridia species, to use a variety of both animal and plant based nutrients making them less dependent on complex carbohydrates.

Note: Two notable differences between obesity and IBS: Both Actinobacteria and E. rectale levels were observed to be increased in obesity but decreased or unchanged respectively in IBS.

What is the best diet for SIBO and obesity?

RUMPS is believed to promote the growth of “good bacteria” and increase gut microbiota diversity. This intuitively makes some sense as RUMPS and other complex fermentable carbs feed or cross-feed many types of bacteria in the gut, most of which reside in the large intestine. RUMPS would therefore be expected to increase the numbers and possibly the diversity of organisms that can participate in carbohydrate breakdown.

But the studies cited above indicate that complex polysaccharides result in more Firmicutes, Actinobacteria and certain Clostridia but less diversity overall due to a decrease in Bacteroidetes and several other Clostridia species. Similar changes are associated with the symptoms of IBS.

The diet that continues to make the most sense for people with SIBO (and obesity?) in my view, is one that limits (not eliminates) fermentable carbs putting the polysaccharide loving microbes on a diet so to speak. Animal-based foods in combination with moderate / reduced levels of fermentable carbs promote bacterial species that metabolize amino acids and other animal-based macronutrients as well as a moderate level of Firmicutes and Clostridia that prefer complex carbs.

Even Dr BG from Animal Pharm says “For SIBO and intestinal permeability, it’s actually healing to minimize fermentation if it is occurring pathologically in the small intestines… where it shouldn’t be.”

How many complex carbs is the right amount?

The best mix of complex carbs to animal-based proteins and fats will depend on the age, health, and gut microbiota makeup of each individual. There are three basic types of diet in terms of fermentable carb levels. At one end is the elemental diet which provides zero fermentable carbs. In the middle are moderate fermentable carb diets which include: low starch, low carb, low FODMAP, and my own Fast Tract Diet. At the other extreme are diets that contain an excess of fermentable carbohydrates including the Standard American Diet (SAD), Vegetarian diets and diets that include fermentable carb supplements such as inulin, fructose oligosaccharide, fiber or RUMPS.

Diets with no fermentable carbs

While elemental diets (predigested carbohydrates, proteins and fats) are very effective at normalizing SIBO symptoms in IBS,[31] going too low on fermentable carbs may not be a great long term strategy. People who are very ill with conditions such as active Crohn’s disease can benefit dramatically (supporting remission) from the elemental diet, however eliminating all fermentable carbohydrates does decrease microbiota diversity which may have negative consequences long term.

One example is the connection between enteral tube feeding with the elemental diet and C. diff infection.[32] The risk of C diff. may be from the diet reducing protective bacteria or their metabolic end products, but there are many other risk factors that may also be responsible including: People in the study were very sick to begin with and often hospitalized where C diff infections are commonly acquired. Patients were often on antibiotics or PPI drugs which both increase the changes of C diff. Also, tube feeding increases the chances of C diff exposure. Regardless, common sense indicates that including some level of fermentable carbs in the diet is the healthy thing to do. In addition to a variety of health benefits from a robust microbiota, we get up to 20 – 25% of our calories from the fats that gut bacteria make.

Diets with high levels of fermentable carbs

High fermentable carb diets include vegan, Standard Amer. Diet or SAD, and diets supplemented with high fiber, prebiotics or RS. Feeding our gut microbes with plenty of fermentable carbs on the surface sounds like a great idea. But we can see that Firmicutes and certain Clostridia bacteria may take advantage of this high fermentation burden in people susceptible to bacterial overgrowth. It’s easy to ignore the many other sources of fermentable material gut bacteria have available including: Unabsorbed proteins, mucus, nucleic acids and other macromolecules.

To make matters worse, people with SIBO often have malabsorption issues – it’s a double whammy. Carbohydrate malabsorption theoretically makes the effective GI of carb-containing foods lower. Therefore people with SIBO likely end up with more fermentable carbs in their intestines after the same meal compared to people that don’t suffer from malabsorption. Also, people with IBS may have an additional source of fermentable carbs, mucin. IBS patients overexpress the gene for mucin production, Muc20.[33] Mucin is a fermentable substrate. Top mucin degraders include Rumminococcus, particularly R. torques, but also bifidobacteria.

Since most people already agree with the monumental problems with the SAD diet, I won’t comment further and limit the discussion to diets that have lots of resistant starch or add RUMPS or other fermentable carb supplements. I have no issue with young healthy people, or older healthy people for that matter, consuming lots of fermentable carbs and there is even some evidence that RS may help with infectious diarrhea. If you’re supplementing with RUMPS and suffering no negative consequences, you have my blessing by all means. But as you have seen in the side effects section, not everyone escapes the negative consequences of excessive fermentation if they include too many fermentable carbs.

Diets moderate in fermentable carbs

Microbiologists estimate that our gut microbes ferment approximately 60-80 grams of fermentable carbs per day to account for one typical day of fecal output accounting for metabolic loss.[34] But how many fermentable carbs are in our diet? To answer this, I developed a formula called Fermentation Potential:

FP = (100-GI)(NC)/100 + DF + SA

GI = Glycemic index, NC = Net Carbs, DF = Dietary Fiber, SA = Sugar Alcohols. Values are in grams/per serving.

Using this formula, I have estimated that typical Western diets actually contain well over 100 grams / day of fermentable carbs. As little as 30 grams of carbs allow gas-forming gut bacteria to produce 10 liters of hydrogen gas. Also, recall the many sources of fermentable material listed above which are available to gut bacteria. Several moderate fermentable carb diets mentioned above reduce the fermentative burden and improve symptoms of SIBO-related conditions. For a review of these diets along with the elemental diet, check out this article on SIBO Diets.

Because I don’t think these other diets go far enough, I created the Fast Tract Diet, and FP system. My goal was to quantitatively reduce hard to digest fermentable carbs to 45 grams per day or less to “quite the gut” so to speak and allow the body’s control mechanisms  including motility, acidity and immune system to clean house reducing the overall number of microorganisms to restore some order from chaos.

Concluding Remarks

We have been endowed through evolution with a huge variety of helpful gut microbes that perform a variety of important functions supporting our health and nutrition. We are just beginning to understand specific growth patterns of gut bacteria in response to diet, particularly fermentable carbs. These patterns will likely be different for different people, especially people who are obese or suffer from SIBO-related conditions. Developing an extensive image of gut bacterial types (phylum/enterotype, genus and species) able to participate in the breakdown of various fermentable carbs and their connection with digestive and autoimmune diseases as well as obesity will help.

While keeping an open mind to the benefits of RUMPS, my own view still leans towards the concept that RUMPS, though potentially less threatening, belongs in the group of hard-to-digest but fermentable carbs, which also include: lactose (for lactose-intolerant), fructose, other forms of RS, fiber and sugar alcohols. I believe limiting all five types is key to getting control of symptoms of IBS, acid reflux and other SIBO-related conditions. But there needs to be balance. I don’t think diets that eliminate fermentable carbs or diets with excessive amounts of fermentable carbs are healthy diet for people with SIBO. I recommend some skepticism concerning RUMPS for people with SIBO or autoimmune-related conditions based on the following:

  • Reported GI side effects from many supplementing with RUMPS that are constant with the GI side effect of RS published in the scientific literature.
  • Anecdotal reports of autoimmune side effects with RUMPS.
  • Early research on gut bacterial enterotypes suggests that overgrowing, carb-loving, gas producing bacteria may be a factor in IBS and obesity.
  • Complex polysaccharides including RS may be reducing, not increasing, the diversity of our gut microbes, feeding blooms of gas-producing bacteria and driving symptoms.

But I don’t want to completely close the door on using RUMPS for treating SIBO for a number of reasons:

  • A few people with SIBO, IBS or acid reflux have reported improvement supplementing with RUMPs – I can’t argue with that if it works. Given the complexity of SIBO and dysbiosis, there may be certain individuals with SIBO who may benefit from RUMPS.
  • There is a plausible mechanism, particularly in the case of diarrhea-predominant IBS – RS is like a bus.
  • The low relative fermentability of RUMPS suggests it may be less symptom-provoking than other fermentable carbs (I learned something new).
  • Careful dosing (reductions) for people with SIBO has not been tried / studied and could provide benefits with fewer side effects.

Of course only time and actual studies in people with SIBO-related conditions will tell us for sure if RUMPS is therapeutic for treating SIBO.

General recommendations

People with SIBO-related conditions suffer from a variety of underlying issues including: intestinal scarring, motility problems, gastroenteritis (infection or food poisoning), malabsorption due to intestinal villi, (needed for absorbing nutrients) damage, digestive enzyme deficiency, immune deficiency, low stomach acid, antibiotic use, or even genetic susceptibility based on Crohn’s, Celiac or other autoimmune conditions.

If you have signs or symptoms of SIBO or dysbiosis, I recommend the following:

  1. Reduce excessive gut fermentation by adopting the Fast Tract Diet that quantitatively limits all difficult-to-digest fermentable carbs.
  2. Work with your own health practitioner to explore, and where possible correct, potential underlying causes of SIBO listed above.
  3. Once you reach a baseline where excessive inflammation, SIBO and symptoms are under control, you can begin to experiment with gradually adding back more fermentable carbs including RUMPS (start with ½ teaspoon with lots of water) and see how it goes.
  4. Your gut microbiota can recover over time provided you don’t overfeed it, avoid antibiotics and address any underlying issues identified in step 2. You can experiment with adding probiotics (lactic acid, bifidobacteria or even soil-based probiotics), but to date, probiotics have not been shown to be very effective for IBS (the exception being some possible benefit for diarrhea) likely because most don’t become established in the gut. The gut is a highly specialized ecosystem in which bacteria have actually evolved the tools to colonize it. Though some probiotics might remain transiently and a few may even become established, rebuilding your microbiota occurs gradually overtime with fecal-oral transfer from house mates likely being one of the most significant sources of gut bacteria that can become established.


  1. Hard-to-digest “fermentable carbs” are quite different from “fermented carbs”. Fermented carbs have already been fermented outside the body in an incubator- think yogurt. Fermented carbs are mostly used up and replaced with short chain fatty acids. Fermented foods (unsweetened) are low carb / low fermentation potential and are safe to eat and encouraged on the Fast Tract Diet.
  2. You can always have your own microbiota tested to see what’s going on.
  3. The next wave of understanding will likely come when we understand how microbiota changes in luminal or unattached bacterial enterotypes relate or not to changes in mucosal or attached bacterial enterotypes in digestive health and illness.
  4. The Fast Tract Digestion books have a whole chapter on identifying and addressing the many underlying causes of SIBO.


[1] Ramakrishna BS1, Venkataraman S, Srinivasan P, Dash P, Young GP, Binder HJ. Amylase-resistant starch plus oral rehydration solution for cholera. N Engl J Med. 2000 Feb 3;342(5):308-13.

[2] Gancz H1, Niderman-Meyer O, Broza M, Kashi Y, Shimoni E. Adhesion of Vibrio cholerae to granular starches. Appl Environ Microbiol. 2005 Aug;71(8):4850-5.

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