Gut microbiome & short-chain fatty acids: resistant starch vs. prebiotics

Bifidobacteria undoubtedly like resistant starch (RS).  They bind and hold on tight, an effect mediated by cell surface proteins.  Big thanks to Tim Steele for passing along many of the studies cited here.  One of said studies showed that treatment of bifidobacteria with proteases abolished the RS binding; but even dead critters would bind if their cell surface proteins were intact (Crittenden et al., 2007).  

I suspect fermented foods have this all figured out.  The microbes in sauerkraut are going to be embedded in & all around the cabbage polysaccharides; likely protected from digestive enzymes (to a degree) and holding on tight.

Something similar has been shown for galactooligosaccharides (GOS) (Shoaf et al., 2006).  In this study, GOS, but not a variety of other fibres, inhibited the binding of pathogenic gut microbes to intestinal epithelial cells.

These mechanisms are likely not mutually exclusive, and both seem like they could benefit the host (us).

Probiotics taken by themselves barely survive the trip (Prilassnig et al., 2007).  This study tested 2 different bifidobacteria-containing products (Omniflora & Infloran)… they recovered none of the supplemented bifidobacteria in the feces from people given Omniflora, and in only 1 out of 4 samples for Infloran.  And in a study by Kekkonen, probiotics alone had little effect on bifidobacteria, but throw in 3.8 grams of GOS and voila!

GOS bifido


If you have long-standing GI issues and suspect dysbiosis: 1) you’re probably right; and 2) fermented foods could fix the problem.  If they don’t, consider: Jane Plain’s eradication protocol of low carb diet plus vinegar, or running a course of pre & probiotics.

Bifidobacteria should ideally be administered with a preferred fuel like GOS, RS, or dark chocolateTzounis and colleagues showed 4 weeks of eating the kind of cocoa flavanols found in dark chocolate tripled the amount of bifidobacteria recovered in fecal samples:cocoa

GOS, 5 grams per day, administered with chocolate induces an even greater increase (Davis et al., 2010). GOS dosage

Note: in neither of these 2 studies did the participants receive any actual probiotics.  Given the findings of Kekkonen, combining bifidobacteria with GOS is likely optimal, and may even allow for a lower dose of both.


Yang (2013) tested a variety of different fibres in an in vitro colon simulator for their bifidogenicity: pectin, guar gum, organic agave inulin, arabinoxylan, beta-glucan, and type II resistant starch (high-amylose corn starch).  Surprisingly, pectin killed it!  > 20x increase in bifidobacteria, compared to 6-7x by inulin & RS  …however, I’m currently viewing this one with skepticism because… pectin beating out inulin and RS?  Pectin?  Warrants further investigation, or at least a human study  (an apple a day?)

Types II & IV RS vs. bifidobacteria
Intervention in this study was 100 grams of plain crackers, or crackers enriched with either 33 grams of type II RS (Hi-Maize 260) or type IV RS (Fibersym).  3 week treatment, 2 week washout, triple crossover (Martinez et al., 2010).

At baseline, 2.1% of microbiome was comprised of bifidobacteria.  After 3 weeks, bifidobacteria was increased to 5.8% by RS II and 11.1% by RS IV.  A 5x increase is nothing to scoff at in a triple crossover study.

Short-chain fatty acids: Resistant Starch
Stewart and colleagues compared the effects of 12 grams of 4 different fibres and maltodextrin for 14 days, followed by a 21 day washout (4-way crossover) on short chain-fatty acid (SCFA) production.   Their RS was type III retrograded starch produced from high-amylose maize starch.  Soluble fibre dextrin comes from tapioca starch.


Butyrate accounted for 33.3% of the SCFAs in RS III group, although total SCFA production was decreased… so overall butyrate production may have been lower.  I imagine in vivo flux measurements are exceedingly difficult, so it’s hard to say if this is confounded somehow.

A significantly more awesome study by Cummings compared 15 days of a starch-free diet to: a fully digestible wheat starch; wheat bran; raw potato starch (type II RS), raw banana starch (type II RS), processed wheat starch (type III RS), and processed maize starch (type III RS).  The dose was 75 grams of raw potato starch per day which, according to their calculations, provided about 30 grams of type II RS (this puts the RS content of raw potato starch at roughly 40% (w/w); slightly lower than Raben’s estimated 54%).

Why I think this study is awesome: it looks like the microbiome of subject “I” had little taste for RS!  And that of subject “J” completely digested potato starch but had no love for banana starch.  non-responders

And for type III RS, the microbiome of subjects “I” & “J” had no problems, but that of “A” didn’t digest any of them.   “D” & “H” didn’t take any maize starch but had no problem with wheat starch, whereas “E,” “G,” & “K” took ’em all down.

Yeah, that’s a very cool testament to individual variability.               THANKS AGAIN, TIM.

As to SCFA production (click to enlarge):fibres scfa

In this study, all of the fibres increased SCFA production relative to the fibre-free diet duh, and the type III RS did seem to get metabolized to butyrate to a greater degree than in Stewart’s study.  This also suggests a subtype-specific effect: RS III produces less SCFAs & butyrate than raw potato starch.

Short chain fatty acids: GOS
Total amount and speed of SCFA production is increased with GOS treatment (in vitro; Bouhnik et al., 1997).  Data in the figure below are taken after 1, 2, 7, and 14 days of GOS supplementation.  SCFA production is measured at time zero, and 2 & 5 hours after adding GOS to fecal slurries (sorry gross I know).  After 14 days of treatment, total SCFAs were increased (compare the 0 time point in days 1 & 14) and faster (compare the 2 & 5 hour time points in days 1 & 14):

GOS bifido in vitro

And in mice, GOS significantly increased total SCFA levels, and markedly increased butyrate production relative to control (Pan et al., 2009):



~~~ conclusion~~~

Raw potato starch vs. GOS
The direct comparison study hasn’t been done and likely won’t.  *sigh*  They seem to perform similarly… which is odd, considering potato starch comes from potatoes and GOS is found in breast milk.

A lot of people have expressed concern over the net carbs in raw potato starch.  Cummings and Raben estimated the indigestible fraction to be 40 and 54% (w/w), respectively.  I get it.  For what it’s worth, I’m convinced that said net carbs won’t impact your blood glucose levels…  however, collectively, the findings above suggest there are a lot of similarities between raw potato starch and GOS.  Both are bifidogenic and both increase SCFA production.  Gram for gram, GOS is more potent than raw potato starch.  And since the common daily doses of raw potato starch are significantly greater than GOS, they’re in the same ballpark price-wise.   Yes, including shipping.

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  • Really great, Bill. Very gratified you have now looked into this enough from the purely research aspects (as opposed to my hundreds of N=1 anecdotes) to recognize there’s there, there.

    The puzzle will become clearer over time.

    I am curious about the purported % of RS in RPS. I believe Tim had found info that it’s about 75-85% RS, the rest moisture (locked up inside the granules, which is why they burst like popcorn at 140F). So, this is something I’ve alerted Tim too, since this is a discrepancy of about 50% in terms of dosage.

    FYI, I have been doing about 8 TBS for a while now. Initially, increased flatulence and that’s pretty much evened out. Biggest benefit is that now, even a glass of whiskey doesn’t give me much heartburn. Speculation is that RPS taken with water on an empty stomach helps flush out the small intestine, giving bacteria a bus ride to the colon where they belong.

    Thanks for the good work.

    • Hi Richard, thanks!

      The %RS discrepancy puzzled me at first, but every study I’ve seen shows the same thing: RPS (or any other form of RS) doesn’t spike blood glucose. So it might be a moot point…? (at least that’s my current thinking)

      As to the bus ride phenomenon, yes, that’s definitely one of the more interesting aspects of RPS (& GOS, apparently).

  • Wenchypoo

    A health food store clerk told me last Saturday that gut flora is killed off with the use of Pancreatin and other digestive enzymes. But what else is a hiatal hernia patient supposed to do when proton pump inhibitors are the prescribed treatment of course for non-stop proton pumps?

    It’s Pancreatin twice daily (after meals) and probiotics early in the morning 30 mins. before eating around here.

    P.S.–the great black-eyed pea experiment takes place tonight. I bought frozen ones and let them thaw in the fridge, so they’d be cold.

    • Melissa

      Some gut flora in some places, but certainly not all gut flora. It’s going to depend how and where they are digested. And by “who.”

      There are also a host of foods with antimicrobial properties. Interestingly chocolate flavonoids have some of these properties but as pointed out in this post, some gut bacteria actually can consume them.

      • agreed. Endogenous digestive enzymes don’t wipe out the gut flora, so why would supplemental ones?

        • Melissa

          I’ve read they can wipe out biofilms produced by pathogenic bacteria, but can’t find the ref now.

    • Don’t believe ’em! I used to work at the Vitamin Shoppe and can tell you first hand, employees receive no training whatsoever. We could read books in the library section, but that’s about it… also, I don’t think it’s true about the digestive enzymes… normal digestive enzymes don’t kill off the gut flora, so why would supplemental ones?

      Keep us posted about your experiment!


    • Wenchypoo

      Well, all I can say about the whole Pancreatin/probiotics thing is this: NO GAS AT ALL LAST NIGHT! Since I forgot to pull out the sugar-killers from his evening pills, we’re going to do the experiment again tonight for more accurate results.

      As for this morning’s breakfast, which was the same foods minus the sugar-killers, the baseline was 94, and 108 an hour later. We’ll be gone during what would be the second-hour’s reading, so we’re going to repeat again tonight.

      So far, I am impressed to say the least. I’m also going to test on other kinds of beans in the future.

      • What are the sugar killers?!

        • Wenchypoo

          Chromium, vanadium, and bitter melon.

          • Wenchypoo

            I got accused of following a “woo-woo” regimen from Free the Animal, and he deleted the whole conversation! He said I bought into a “woo-woo miracle cure” and that there IS no oral analog to insulin–boy is HE wrong! Even WebMD has a page on bitter melon as a BG lowerer:


          • I think *all* of the n=1’s for RPS should be posted, not just the stellar ones… so please, feel free to post any or all of that conversation here!

            Also, I do agree with you –> diet & the right combination of supps can significantly reduce the need for insulin in type 2’s.

      • Wenchypoo

        Tonight’s test results: baseline 100, +5 points after 1 hour, and yes, I removed the sugar-killers before feeding him. Still no gas. The spike gets lower and lower! Can’t wait to see what tomorrow’s FBG is.

  • On the question of the RS content of raw potato starch, Tim write in email:

    “There are a few older studies that measured RS differently — when they come up with 50% for RPS, they also get 30% for Hi-Maize. Newer testing, or old ileostomy testing keeps RPS at about 80% and Hi-Maize at 50%.

    “Some studies use an ‘RS as fraction of Total Starch’ where others use ‘RS by weight of product’. That threw me for a long time, too.”

    • Aaah. I see. Makes sense. The numbers I was using are % by weight (grams RS per 100 grams of product).

      Seems like measuring RS in stool samples could be tricky, and affected by a lot of experimental variables… although I generally don’t discount old studies simply for being old, I can see newer ones having an advantage in this capacity. Eg, it used to be notoriously difficult to measure glycogen in liver samples because it was degraded within seconds of taking the biopsy. Then newer [better] techniques came along and the data improved, became more reproducible. So I can easily see the RS content of RPS being greater than 40-54% (w/w).

      • Phil Thompson

        At the bottom of there’s a collection of RS values as a percentage of starch in sample. Potato is about 80% RS of starch present. Table 1. In Table 2 RS is reported as 63% of sample “as is”. At 20% moisture these are about the same.

        • Thanks for the link! Those numbers are pretty close to what I’ve seen.

          But regardless of whether it’s 40, 54, or 63%, I don’t think it matters *too* much because in every study I’ve seen, no form of resistant starch causes a spike in blood glucose. What do you think?

          • Phil Thompson

            That’s true. A fair proportion of the non-resistant starch is labelled “slow digesting” so perhaps it enters the bloodstream at a clinically insignificant rate.

  • Melissa

    Wait does that mean I can just eat chocolate instead of potato starch? I would very much prefer that haha.

    I am curious to see how people who came to LC via gut issues react to potato starch, particularly those of us who came via SCD and other LC and LC-ish diets that work by reducing fermentation in the gut. I only managed two weeks but it was very unpleasant. I have had similar reactions to inulin.

    You can ultimately change the balance of your gut bacteria, but little evidence you can change the resident species. Let’s see someone has a pathogenic type of prevotella, like P. copri implicated in rheumatoid arthritis– they are going to have much different results from getting a carb-fed lower gut microbiome compared to someone who has different types of prevotella.

    • Reducing fermentation via low carb does seem effective for some, and the proposed mechanism whereby potato starch binds microbes in the upper gut and traffics them to the lower gut seems like it could [theoretically] complement this…? but I’d also like to see how it plays out in a good crossover study.

      Just curious, have you tried Bimuno? GOS technically aren’t FODMAPs, and the dose is usually about 3-5x less than inulin.

      As to the resident species… agreed. The Prilassnig study tested 6 different probiotic products, and very few of the supplemented species were recovered in stool samples. And results from the Kekkonen study suggest that even if they are, they’re dying off within a week or two from when supplementation is discontinued.

      • I like the idea that GERD is a symptom of SIBO rather than the purported “too little stomach acid.” My dad and all 4 of his kids were lifelong GERD sufferers. I was on PPIs for years and coincidentally, when I went on them, thought them a miracle from God…that’s when my weight began a more rapid ascent.

        If it’s too little stomach acid, then how come when I take a heaping tsp of baking soda in water of club soda do I get minute long belches? I’m talking huge.

        Paleo, of the LC variety, really handled GERD quite well, but only for about 3 years, and then it cam back gradually.

        Guess why, I think? Because I stopped doing my routine 24-30 hr fasts weekly. I exchanged emails with Norm Robillard (the SIBO/GERD guy) and he told me that fasting is a sure fire way to control SIBO.

        So, I wonder. How about potato starch in water on an empty stomach, coupled with a good 30 hour fast once per week…..

        Makes evolutionary sense to me.

        • Interesting. The IF (or even intermittent LC low-fibre diet) + RPS protocol seems like it could benefit a variety of GI issues related to dysbiosis.

      • Melissa

        I am curious about the Bimuno, seems the the site is UK though? Might make it a bit expensive to ship.

        I am shocked that there are no studies I can find on RS in IBS. That is very strange. Inulin IBS studies either tend to show negative results or nothing.

        I don’t have issues with GERD anymore. I eat other foods with anti-microbial properties so maybe those control upper GI bacteria. Who knows though.

        • Bimuno is a UK company, but I know a few people who ordered it. Shipping to US is about $7 according to their website.

          There really aren’t a whole lot of studies on RPS in humans for anything, not just IBS (although that does seem like an obvious target).

        • Erica Nehrling Meador

          Maybe try VSL#3 probiotic? Also try looking into some of David Topping’s research. He is a world-renowned expert on resistant starch and intestinal health. Best of luck.

    • grace/DrBG

      M~ I’ve had intolerance too but it maybe a metal intolerance.

      Great post. What I’ve concluded is that PS is like other fiber — similar fermentation patterns and post-prandial insulin responses, very similar to psyllium. However it does not have many if at all studies for weight loss, body fat recompositioning, BP reduction or BG/Hgba1C improvements as other fiber.

      Studies on rodents are very disparate. Rodents eat their own and cagemate’s poo. THis affects the microbiota and thus the results IMHO. Also when lab animals (like humans) are moved to different buildings or even different rooms, the study outcomes can change…

      Here one study shows RS does not produce butyrate more than HAM, and another study shows the opposite.

      THUS I think it really depends on what is in your zoo cages (microbiota)! Unfortunately the AmGut which Tim and Lauren did recently are nice but they nothing of the pathogens, protozoa, fungi or other pathogenic overgrowths in the gut…

      • Hi Grace, thanks!

        And thanks for the links. Very cool to see direct comparison of inulin/FOS and RS.

        Interesting that it took so long for SCFA production to level out (28 days in Henningsson study & 44 days in Perrin study?).

        As to the contradictory findings in Henningsson vs. Martin… I expect human studies to be much, much worse 🙁

        AmGut isn’t the whole picture, but it’s a start! it’s probably extremely cost-limiting to get a more comprehensive analysis done.

        • grace/DrBG

          Bill~ Thx for your discussion on the microbiome and the exploration on how it impacts health. I agree the humans studies are all very conflicting, particularly yogurt ones — some show clear clinical and therapeutic benefit, others NADA. Results depend imho on the critters that live in the gut and caecum — the house for the critters and the spectrum of fiber they are feed. Tony Hoffman who used to be at Genova Diagnostics (GDX) once told me that the FMTs (fecal microbiota transplants) fail after 1-2 years per communication with the researchers. There is a suspicion that the caecum reverts to prior, original species. OTOH I see shifts on the GDX GI Fx stool profile when people address the pathobiont and parasitic growths. Here’s my pre- and post-charcoal/clay and kraut labs.

          Ancestrally I’d conceded that hominids never ate RS alone in single isolation. Fiber occurred in a spectrum — inulin, oligosaccs, arabinogalactans, xylans, pectins, hemicellulose, cellulose, RS, etc. To me VLC diet + RS alone is kinda un-ancestral, unnatural and sorta freaky. I suspect too that raw potato starch may fail to be carried to the distal colon without bulking agents like other fibers (inulin, hemicellulose, cellulose, etc).

          In the rodent studies there is a suggestion that the full suite of fibers provide synergistic and complementary feeding to the microbiota.

          RS alone or NSP/FOS/etc alone do not appropriately feed the critters because butyrate production is shown to fail or not be as robust in several studies.

          Here RS, FOS, pectin and cellulose exert mixed fermentation effects whether singly fed or in mixed substrates. “The results showed that the mice body-weight gain was the smallest (7.0 ± 2.3 g) when the mixture of RS-FOS-cellulose was ingested, followed by the mixture of RS-cellulose (7.2 ± 3.5 g) and FOS-cellulose (8.3 ± 2.5 g).”

  • Great blog. Look forward to revisiting in the future.

  • Mario

    Hey Bill,

    Does it make any sense, and what does it indicate, that while I was experimenting with RPS, my Ketostix were always nice and dark. When not using RPS, Ketostix always indicated small…


    • Hi Mario, I touched on that at the end of this post: Check it out and let me know what you think.

      • Mario

        will read it later on today after my traditional New Year’s Day ikea furniture assembly…

      • Mario

        Hey Bill, re-read both posts and I’m more baffled by my Ketostix’s darker colors when using RPS.

        I’m currently experimenting with GOS and some probiotics, but haven’t been taking them as you’ve suggested, which I will start doing so tomorrow along with some dark chocolate.

        After I’m done this 30dsy round of GOS, I may give RPS another try, and hopefully won’t get kicked outta the house because of the gas…


        • Keep testing the ketones and keep us posted! (this is uncharted territories, clinically speaking)

    • Chris

      were you in an energy deficit state while having rps in ketosis? I mean, were you ingesting fewer calories than your BMR ?

      • +1

      • Mario

        energy intake was the same when having RPS, and when not.

        • I think what Chris meant was: negative energy balance. Maybe total energy expenditure was slightly higher on those days (something people generally don’t notice)…?

          • Mario

            Energy expenditure was also the same.

  • Dave

    Quite different but still related: what does kashi put in their cereals “go lean” ? I had never experienced so much pain in my intestines 🙁

  • Wenchypoo

    Question: are you folks testing RS foods WITH or WITHOUT using insulin, supplements, normal? I just got done reading Free the Animal’s latest RS article, and apparently they’ve been testing while continuing to use insulin, pills, etc.

    Should I have been doing the same? I’ve been testing raw (without them). Hubby’s sugar-killers are chromium (1000 mcg. X3), vanadium (20 mg.) and bitter melon (450 mg.) twice daily (after meals).

  • Mario

    I started using the white (legal) stuff (RPS) again yesterday morning, 40gr at 10am.

    Later on in the day I had a little bit of GERD, which may be why I stopped using the last time.

    At around 11pm I had a bit of gas, just in time for bed, my poor wife…

    Haven’t had any dreams for the longest time, but last night I had two; (1) about a friend’s son walking around my parents house, where he’s never been, without a shirt on, exposing his ab’s to my brother and I who were eating breakfast… (2) the family and i were in some apartment, knock on the door, unknown woman answers, struggle ensues, she gets stabbed, assailant flees, my brother goes to see what’s up, i follow, and see blood squirting out of her wound, hitting the wall.

    Checked ketones with Ketostix this morning after shoveling snow and ice for one hour, they were at “trace”… Normally I do test upon waking, but not this morning.


    P.S. Will continue at 40g/day and post updates here daily.

    P.P.S. Gas just started again – home alone = no victims.

    • Awesome awesome awesome. I definitely look forward to your updates. Thanks! Plz monitor body weight too, if it’s not too much of a bother… I think that, more than a lot of other factors, impacts ketonuria on VLC diets.

      Dreams: very interesting. Crazy/scary/weird, but interesting.

      P.S. “no victims” hahaha!

      • Mario

        Body weight, no problem! Before the holidays it was 145lbs, this morning it was 150lbs – i REALLY over indulged in almond butter over the xmas break…

        Not much gas yesterday, and no GERD.

        I did have indigestion while nearing the end of a 9oz tuna steak… All of a sudden I felt full and couldn’t eat anymore, afterwords felt as if I might puke, but didn’t. Not sure if this is relevant but included it anyway.

        Ketostix still showing between trace and small.

        Two relatively normal dreams last night, both similar and related.

        Up’d RPS to 60gr today.


        • 60 grams! can’t wait to hear about this…

          how are you preparing it?

          • Mario

            To my surprise, I haven’t had anywhere near as much gas as I did when I first started using it weeks ago.

            Also, Ketostix are still showing trace or small, so maybe I was in fact doing something differently before.

            60gr didn’t seem to make any difference compared to 40gr.

            I mix RPS either with half-a-serving of Vega Sports Electrolyte Hydrator and 500ml of water OR with 125ml of coconut water and 375ml of water. Fluids are either room temperature or cold…

            No dreams last night that I can remember…

            BM’s and constipation seem to have improved, will give it another week before confirming for sure…


          • I think ketostix will remain low until some of those almond butter pounds start coming off… just a theory, though.

            it’s pretty interesting that you upped the dose by 50% and dreams went back down to nil…

            Are you at a point where you feel like you could compare PS to GOS? Not gram for gram, of course, because I’m pretty sure 40 grams of GOS would kill you.

          • Mario

            My first round of PS lasted 2 weeks, and I specifically remember saying to myself on several occasions that “I feel great” – mainly because constipation seemed to subside.

            I stopped PS when the GOS arrived from the UK, and I did 3 weeks of that – poor digestion and constipation returned.

            When I checked with Ketostix the last couple of times, it showed 4mmol/L, which is going in the right direction – will keep monitoring and posting.

          • Mario

            Back to 40gr today, and for some reason lots ‘o gas…

            Ketostix are getting darker, faster.

            No dreams that I can remember last night.

            BM’s are great and no signs of constipation…

          • getting any closer to pre-holiday body weight?

          • Mario

            Will get on the scale tomorrow morning upon waking up, which is when I normally weigh myself, and reply back.

          • Mario

            151.5lbs up 1.5

          • ketostix still showing low ketones?

          • Mario


  • Mario

    Body weight, no problem! Before the holidays it was 145lbs, this morning it was 150lbs – i REALLY over indulged in almond butter over the xmas break…

    Not much gas yesterday, and no GERD.

    I did have indigestion while nearing the end of a 9oz tuna steak… All of a sudden I felt full and couldn’t eat anymore, afterwords felt as if I might puke, but didn’t. Not sure if this is relevant but included it anyway.

    Ketostix still showing between trace and small.

    Two relatively normal dreams last night, both similar and related.

    Up’d RPS to 60gr today.


    P.S. Sorry for double post…

  • Pingback: Gut microbiome & short-chain fatty acids: r...()

  • Mario

    Feeling pretty good with 40gr/day.

    My digestion and BM’s have been great! I seem to be regular again… which has always gone away whenever I (re-) start LC/Keto.

    Will weigh myself tomorrow morning…

    I haven’t really had any dreams that I can remember… Last night I was pretty sure my wife woke me with some snoring and a burp, but she denies that sort of thing and claims I MUST have been dreaming… lol


    • These are epic updates!

      So, are you thinking the dreams may have been a coincidence?

      Also, is there a reason why you’re changing the dose?

      • Mario

        Regarding the dreams, I have no idea.

        As for the dose, I had second thoughts about jumping up to 60 after only a few days at 40. As I mentioned earlier I feel better than I have, and I think it has a lot to do with the regular BM’s. When I’m constipated, it only takes a day of not going to make me feel uncomfortable and I quickly become a grumpy old man – so my mood is also better, for one reason or another…

        • Thomas Hemming Larsen

          Do you take RPS with a meal or in between?

          I sure agree with you on how constipation can affect your mood. I’ve felt awful, both mentally and physically, after days of not going. Then when it finally happened it was like I had won the lottery.

          • See here:

            My advice (based on Mario’s experience): ALWAYS WITH A MEAL!

          • Thomas Hemming Larsen

            Haha, thanks for sharing. Btw, I haven’t heard back on the ‘Danish’ PS – I’ll get back as soon as I hear something.

          • Thomas Hemming Larsen

            I talked to the company making the potato starch. The starch is made from raw potatoes and they are only heated slightly in the process, not anywhere near the temperature where the starch is affected (he emphasised that).
            He was of the opinion that all of the starch is resistant starch, although he phrased it as none of it could be digested. The flour is 80% starch and 20% water I guess it could be true.

          • I don’t believe him! It’s only been measured in a couple studies, but no one has reported that there isn’t any digestible starch in PS.

          • Thomas Hemming Larsen

            His wording was ‘its my impression that none of it is digestable’ so he wasn’t that firm. In any case, I think this is option with the most RS (70-80% I would assume).

          • Mario

            Usually just before a meal, so with food, and gas is minimal. But on an empty stomach and without food, gas is potent…

          • Thomas Hemming Larsen

            Hehe, thanks.

  • Mario

    My gas situation was apocalyptic yesterday! Good thing I was with family all day long – it was kinda funny listening to them trying to figure out my fart fest.

    Don’t know what the deal was, but I’ve been taking 40gr of RPS either a short while after a meal, or with the meal or just before. Yesterday I took it first thing in the morning, on an empty stomach, and didn’t eat any food until a couple hours afterwords. I’d say within 4 hours of consuming the RPS, my concerto in a(ss)-minor started and continued all day long.

    Luckily I am still allowed in the house.


    • Hahaha! that’s pretty funny. 4 hours is really fast!

      Take-home message: RPS always with a meal; never on empty stomach.

      • Mario

        Is 4hrs possible? Or could have been something the day before?

        • It could’ve been something the day before; but 4 hours isn’t impossible. In general, transit time is ~18 hours, but if PS swelled up a little in the upper intestine, it could push things along in the lower intestine.

          • Mario

            Think you’re right again, Bill!

            Was at my folks house Saturday night, might have over-eaten, and had lots of cheese, which I’ve suspected for some time, that it backs me the f up… Didn’t have a BM until much later in the day Sunday, and it wasn’t as they have been since starting RPS.

          • Mario

            So I guess the gas comes out whichever end has the weakest sphincter!? lol

          • GERD or gas. Ha!

  • Dose frequency.

    Eg, has anyone tried 20 grams twice/d vs. 40 grams once/d? I can see theoretical advantages & disadvantages with both methods…

    • Mario

      I have to constantly shake or stir the 40gr dose, two 20’s may be easier to consume, and would have less severe gas-i-ness.

      • less gas, but hopefully still maintain the other benefits of PS…

        • Thomas Hemming Larsen

          Why would the benefit be smaller if it is 2x20g/day vs 1x40g/day (and vice versa)?

          • 100% speculation. 20 grams twice daily would be bifidogenic all day long…? Also, with less substrate, maybe less gas?

            On the other hand, there might be a threshold dose, whereby all 40 grams need to hit the gut simultaneously.

  • Mario

    Continuing on with 40gr/day, all at once, first thing in the morning, along with my probiotics. Followed immediately by breakfast. This seems to work best for me.

    Will post update on weekend, and will include a weigh in… Trying to cut down on the added fat I add to meals, as well as my snacking and grazing – it’s making me fat(ter)…

  • Thomas Hemming Larsen

    Chris Kresser was on the Underground Wellness podcast recently. He suggests starting slowly with RS at1/4-1/2 teaspoon and then gradually increase it to 1-2 tablespoons.

  • Mario

    Weighed in at 149.5lbs, down 1.0lbs

    • …any ketones?

      • Mario

        Ketostix typically show something between 0.5 and 1.5 mmol/L, occasionally a little darker, but not quite 4mmol/L. It’s been rare that they’ve been darker than 4mmol/L.

      • Mario

        Chronologically… When I wake up, the stix indicate 0,5mmol/L and as the day progresses they get a bit darker, up to 1.5mmol/L. Occasionally they’ll get as dark as 4mmol/L, but not to often, and even rarer is darker than that.

  • Mario

    I stopped taking RPS two days ago, I could no longer guess whether it was gas coming out or something much messier… Luckily I didn’t have any accidents, but I think it was only a matter of time…

    Also, it just seems so un-natural to be consuming it, and it is kind of a pain in the ass to always be stirring… Then I’m also left wondering, is this stuff causing me other unknown long-term issues, or how many carbs am I digesting, and if I am going to be ingesting carbs, I really want to enjoy them, not suffer through them. Using something inulin powder, if/when I don’t have GOS around seems like a much better and more practical thing to be supplementing with, as opposed to 40g/day of RPS, which also has caused me a bit of bloating – nothing uncomfortable, but I noticed it when getting undressed…

    For those that want to eat potatoes and other carbs, and/or that are diabetic, RPS may be a great thing for them, but not for me – so I quit!

    • The Great RPS Experiment: Life, When You Can Never Trust A Fart.

      You did an awesome n=1 experiment. Thanks much for reporting all of your findings.

      Also, I tend to agree about the dose differences. 3 grams of GOS seems safer than 40+ grams of RPS if you’re trying to keep carbs at a minimum. I’m fairly convinced that some people’s guts will be able to digest more or less of the starches in RPS (as per the Cummings study in the post).

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  • Ripley

    William, I believe there’s an error in this article. GOS isn’t found in breast milk. GOS is added to infant formula. Human milk oligosaccharides (HMO) is found in breast milk, but GOS isn’t.

    “The emerging evidence for the biological effects of HMO on the breast-fed infant created a rationale to add oligosaccharides to infant formula to provide formula-fed infants with the same benefits that breast-fed infants receive with their mother’s milk. The challenge has been to identify ingredients that provide HMO. Some HMO are also found in the milk of other mammals but usually at much lower concentrations. Other HMO are unique to human milk, especially the ones with more complex structures. In other words, HMO were simply not available to be added to infant formula. The search for alternatives led to GOS and Fructooligosaccharides (FOS) (Fig. 6), which are synthesized by bacteria and plants, respectively.”

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  • Dan

    I have a question! 🙂

    I have extracted the starch from the crunched raw potatoes in a panty. If I cook/roast these potatoes without the starch and I cool it again, will it contain retrograted resistant starch?


    • Hi Dan,
      Once the starch is removed, how much starchless potato is left? Anyway, I don’t think so. RSIII generally comes from RSII; if you’ve removed all the RSII via extraction, then I don’t think there would be anything left to convert into RSIII…

      • Dan

        Thank you!! 🙂

        • Dan

          What do you think about cooked onions? It contains inulin, which is fermented by the gut bacteria, but onions are also antibacterial. Just like garlic contains inulin does more harm than good to the gut lining and flora in my view.

          • oligosaccharides like those found in onions and garlic aren’t affected by heat like RPS is… so they are likely decent sources of prebiotic fibre.

  • Krista saurus

    Hi I’m curious about all this. It seems to me that when I consume fermented foods or most probiotics, my dopamine increases along with revving up my thyroid, lowering my estrogen and gaba and serotonin. I’ve been unable to east fermented foods for three years our take most probiotics because they do indeed affect my gut bacteria but not in a positive way. I need my estrogen and without 5htp I’m a complete insomnia. This all happened around the time I was exposed to massive doses of wheat dust and/or pesticides, not sure which. Any clues as to how to restore my balance? I remember rhamnosus and longum seemed ok, at sensible doses. Even resistant starch was problematic. Thanks