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How Resistant Starch Will Help to Make You Healthier and Thinner


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resistant starch potato, raw potato starch
Potatoes and other foods are good sources of resistant starch. istock.com/peangdao

I asked Dr. Amy Nett, MD, to contribute this guest post. Amy initially completed her medical training in radiology at Stanford University Hospital, but wanted to work more directly with patients, helping them to prevent and reverse chronic disease and truly transform their health.  Combined with her passion for nutrition she decided to pursue a career in Functional Medicine.  You’ll be hearing more from Amy in the future!

Over the past several years there has been an exponential increase in the number of studies linking imbalances or disturbances of the gut microbiota to a wide range of diseases including obesity, inflammatory bowel diseases, depression and anxiety (1,2,3,4,5).  One of the best ways to establish and support a healthy gut microbiome is by providing the right “foods” for your gut bacteria.  These “foods” are called prebiotics.

Why you should add resistant starch to your diet. #healthydiet #resistantstarch #gutdisgestion

Prebiotics are indigestible carbohydrates, or at least indigestible to us, that reach the colon intact and selectively feed many strains of beneficial bacteria.  Prebiotics are generally classified into three different types: non-starch polysaccharides (such as inulin and fructooligosaccharide), soluble fiber (including psyllium husk and acacia fibers), and resistant starch (RS).  Each of these types of prebiotics feeds different species of gut bacteria, but among these, RS is emerging as uniquely beneficial.

The distinctive benefits of RS seem to be unequivocally recognized, even amongst advocates of a low carbohydrate diet

What Is Resistant Starch?

Resistant starch is a type of starch that is not digested in the stomach or small intestine, reaching the colon intact.  Thus, it “resists” digestion.  This explains why we do not see spikes in either blood glucose or insulin after eating RS, and why we do not obtain significant calories from RS.

There are four types of resistant starch:

RS Type 1: Starch is physically inaccessible, bound within the fibrous cell walls of plants.  This is found in grains, seeds, and legumes.

RS Type 2: Starch with a high amylose content, which is indigestible in the raw state.  This is found in potatoes, green (unripe) bananas, and plantains.  Cooking these foods causes changes in the starch making it digestible to us, and removing the resistant starch.

RS Type 3: Also called retrograde RS since this type of RS forms after Type 1 or Type 2 RS is cooked and then cooled.  These cooked and cooled foods can be reheated at low temperatures, less than 130 degrees and maintain the benefits of RS (6).  Heating at higher temperatures will again convert the starch into a form that is digestible to us rather than “feeding” our gut bacteria.  Examples include cooked and cooled parboiled rice, cooked and cooled potatoes, and cooked and cooled properly prepared (soaked or sprouted) legumes.

RS Type 4: This is a synthetic form of RS that I’m including for completeness, but would not recommend.  A common example is “hi-maize resistant starch.”

Once RS reaches the large intestine, bacteria attach to and digest, or ferment, the starch.  This is when we receive the benefits of RS.

How Resistant Starch Impacts Our Health

The normal human gut has hundreds of bacterial species, some good and some not so good.  The overall number and relative quantity of each type has a profound effect on our health and well being.  Resistant starch selectively stimulates the good bacteria in our intestines, helping to maintain a healthy balance of bacteria (7).

These good bacteria “feed” on RS and produce short chain fatty acids (through fermentation), the most significant of which are acetate, butyrate, and propionate.  Of these three short chain fatty acids (SCFA), butyrate is of particular importance due to its beneficial effects on the colon and overall health, and RS appears to increase butyrate production more when compared with other soluble fibers (8).

Butyrate is the preferred energy source of the cells lining the colon, and it also plays a number of roles in increasing metabolism, decreasing inflammation and improving stress resistance, as described in more detail below and previously in this great article by Stephan Guyenet.

Resistant Starch Helps to Lower Blood Glucose Levels and Improve Insulin Sensitivity

Insulin resistance and chronically elevated blood glucose are associated with a host of chronic diseases, including metabolic syndrome.  Several studies have shown that RS may improve insulin sensitivity, and decrease blood glucose levels in response to meals (10, 11, 12).  In one study, consumption of 15 and 30 grams per day of resistant starch showed improved insulin sensitivity in overweight and obese men, equivalent to the improvement that would be expected with weight loss equal to approximately 10% of body weight (13).

Further, RS has been shown to exert a “second meal effect.”  This means that not only does RS beneficially decrease the blood glucose response at the time it’s consumed, but, somewhat surprisingly, blood glucose and insulin levels also rise less than would otherwise be expected with the subsequent meal (14).

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Why the Popular Press Has Touted Resistant Starch as a “Weight Loss Wonder Food”

RS appears to have several beneficial effects that may contribute to weight loss, including decreased blood insulin spikes after meals (as discussed above), decreased appetite, and decreased fat storage in fat cells.  There may also be preservation of lean body mass, though further studies in humans are needed to confirm if there is a significant impact in overall body weight (15).

Further, several studies have shown alterations in the gut microbiome in association with obesity, which subsequently change towards that seen in lean individuals with weight loss (16, 17).  For example, one study demonstrated that the relative composition of the gut microbiota of two predominate beneficial bacteria, Bacteroidetes and Firmicutes, varied considerably in association with body composition. 

Specifically, obese individuals often have a higher proportion of Firmicutes to Bacteroidetes, which may be reversed with weight loss, gastric bypass surgery, or treatment with prebiotics (3).  However, not all studies confirm a significant or measurable change in the composition of the microbiome in obese compared to lean individuals, and further studies are needed (18, 19).

Butyrate Plays an Important Role in Gut Health and Decreasing Inflammation in the Gut and Other Tissues

As mentioned above, RS intake allows for increased production of butyrate by our gut microbes.  Butyrate acts as a powerful anti-inflammatory agent for the colonic cells, and functions to improve the integrity of our gut by decreasing intestinal permeability and therefore keeping toxins in the gut and out of the bloodstream. (20, 21).  

The SCFAs that aren’t utilized by the colonic cells enter the bloodstream, travel to the liver, and spread throughout the body where they exert additional anti-inflammatory effects.

Resistant starch is also associated with decreased risk of colorectal cancer, thought to occur through several different mechanisms including: protection from DNA damage, favorable changes in gene expression, and increased apoptosis (programmed cell death) of cancerous or pre-cancerous cells (22, 23).

Adding Resistant Starch to Your Diet

Some common food sources of RS include green (unripe) bananas, plantains, properly prepared cooked and cooled parboiled rice or legumes, and cooked and cooled potatoes.  See this link for a more complete list of RS quantities in food.

However, if you are on a low carbohydrate diet or don’t tolerate those foods well, you can add RS to your diet without adding digestible carbohydrates.

Bob’s Red Mill Unmodified Potato Starch (NOT potato flour) is one of the best sources of RS with approximately eight grams of RS in one tablespoon.  Potato starch is generally well tolerated even by those who react adversely to nightshades.

Plantain flour and green banana flour are also excellent sources of RS, and there may be benefit to including all three of these sources (specifically alternating your source of RS rather than relying on a single one).

These are relatively bland in flavor and can be added to cold or room temperature water, almond milk, or mixed into smoothies.  But to maintain the benefits of RS, these should not be heated above 130 degrees.

Tim Steele (Tatertot) has written about some of the research on RS supplementation, and in particular the potential further benefit of combining potato starch with psyllium husk fiber to even further increase butyrate production in the colon.

Take It Slow

If you choose to try supplementing with RS, start with small doses of about ¼ teaspoon once daily, and very gradually increase the amount as tolerated.  Some increased gas and bloating is expected as your gut flora changes and adapts, but you do not want to feel uncomfortable.  If you experience marked discomfort, then decrease the amount you’re taking for a few days until your symptoms resolve, and then try increasing again gradually.

Studies indicate that the benefits of resistant starch may be seen when consuming around 15 to 30 grams daily (equivalent to two to four tablespoons of potato starch).  This may be too much for some people to tolerate, particularly in the setting of gut dysbiosis, and going above this amount is not necessarily beneficial.

If you experience marked GI distress with even small amounts of RS, this may be an indication of SIBO (small intestinal bacterial overgrowth) or microbial dysbiosis, and you may need to consider working with a healthcare practitioner to establish a more balanced gut microbiome through the use of herbal antimicrobials and probiotics before adding RS or other prebiotics.

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Join the conversation

  1. I had gastric bypass in January 2012. I had diabetes at the time. I’ve maintained my weight loss but my blood sugar levels still require 2000mg metformin and my hba1c is 8. given the gastric bypass will resistant starch workin helping me lower my blood sugar so I may be able to stop metformin?

  2. I have had chronic constipation for 25 years now- in 2 types of medication (constella and miralax)- went vegan- completely re adapted my diet and lifestyle. I am curious how resistant starch such as Bob’s red mill would benefit someone with my problem.
    Would love to know what you think? Could this help me? If so how much I should take? Thank you 🙂

  3. When I cook potatoes, do I need to cook them below 130 degrees like the green banana and plantain flour?

  4. Does anyone know if Konjac Root can be supplemented for potato starch with similar results?

    • I think it can have similar results as prebiotic but as the article states potato starch or RS is better for increasing the butyrate. I think adding konjac root with potato starch would be a good option. I’ve read somewhere that RS is more effective in conjunction with soluble fibers like konjac root.

      • While consuming konjac root *can* make you feel fuller longer, it can also increase constipation because it slows your digestion (hence the feeling of fullness)… just be aware that a little goes a long way. 1 teaspoon daily was enough to seriously “gum” up the works for me (I am on a low carb diet) and it took me several months before things started to get back to normal.

  5. Anyone know if cooked steel cut oats chilled overnight in the fridge would have significant resistant starch?

  6. Not sure if anyone will answer this but:

    Can I now use RS (Potato Starch) and Psyllium Husk as a Prebiotic?
    I no longer have to buy a prebiotic powder or tablet because i can make up my own?

    • Yes I’ve read about a few people making their own, I personally just started using potato starch and acacia fiber. Some people use inulin or other fibers depending on preference.

  7. RS Type 3 has to be cooked and cooled.
    1) How long does this type of food have to be cooled for the retrograde RS to form?
    2) Does it have to be cooled in the fridge or room temperature is enough?

    • Yes it’s like to know this too! I’ve also read that you can reheat again without losing (or even improving) the bebedores, is this true?

    • The article says the food needs to be less than 130 degrees. Use a meat thermometer to check it.

  8. Hi Chris, I’m one of those people that unfortunately cannot take advantage of the awesome benefits of Resistant Starches, and in turn I have terrible flare ups of my IBS when I have resistant starch.

    I found your article when searching for information about how to avoid RS… it seems that most resources are ways to get more RS, versus the other way around. I’ve been using the information you (and a few other pro’s) have provided about RS as a form of ‘what not to do’ in my case since I have to avoid them!

    Would you be willing to write and post an article about how to AVOID RS for people who cannot tolerate it? From your article and what else I’ve read, I can gleam that I need to avoid leftovers with rice and cold potatoes, and that I shouldn’t eat unripe bananas or use plantain flour or plantain chips.

    Is there any other information you could provide? Do cooked and cooled quinoa and tapioca have RS? What about sushi rice? How about baked goods a few days later (ex: a couple day old muffins?)

    Also, reheating rice to 130 degrees… is there a way that I can gauge how to do that in the microwave, and will this reduce RS enough… or should I just avoid leftover rice altogether?

    Any additional insight you might have would be great!!! Myself and many others that are struggling with IBS would appreciate it 🙂

    • Look into the book Fast Tract Digestion IBS and fermentation potential info it has that should help you out. I believe you can adapt and become tolerant to things that typically bother you in some cases. Not consuming any gut critter food can be bad too though. Theres lots of info on IBS foods but it is confusing and contradicting. Learn more and go by your “gut”. =)

      • I second “Fast Tract Digestion” by Dr Norm Robillard. He has a website and has written at least 2 books. Carolina–have you read much about avoiding high FODMAP foods? That’s where I started (the book by Patsy Catsos) and then I came across Norm Robillard’s work much later. I’m actually trying the potato starch, slowly, and doing ok. But my IBS is fairly mild, compared to that of many sufferers. I’ve lowered my inflammation levels over several years and I think that has made a difference.

    • Maybe bad bacteria die off when you introduce prebiotics for good colon bacteria that RS is. Sauerkraut is a proven source of good probiotics that possibly over a few weeks could displace not so good bacteria strains.

  9. Hi there, I’m hoping someone can help me. I’ve been taking unmodified potato starch for almost a week now (I’m up to 2 teaspoons a day with a probiotic), and while it’s been fantastic for my skin already, I’m experiencing some pretty severe adrenal fatigue symptoms like brain fog and insomnia. Has anyone else experienced this? And does it go away as your body adapts? Thank you!

    • Are you sensitive to nightshades? I am, so while most apparently can tolerate potato starch, I do not. After taking it for several days I get pain and fatigue.

  10. I really appreciate this article. I’ve been using RS for about 6 months now and my stomach has definitely improved. I’ve been able to step down my stomach medications drastically and can eat certain fruits and vegetables again without discomfort. I’ve also noticed that I don’t get shaky or extremely irritable if I haven’t eaten in a while. I haven’t lost very much weight, but I also suffer from an underactive thyroid, so that’s that. But overall, I’m really pleased with my results. And I’ve read from a lot of the comments that the Bod’s Red Mill doesn’t work. But it does for me! It’s what I’ve been using all along.

  11. WRONG–per phone call with Bob’s Red Mill on November 3, 2016: The rep told me that their Unmodified Potato Starch (not potato flour) is NOT a resistant starch due to the way their manufacturer makes it. I relied on the info in this article and several other sources on web that recommended Red mill potato starch for RS when I started my Ketogenic diet 7-1/2 months ago. Even tho I kept my daily net carbs below 20g, I barely lost any weight. Now I discover all that effort was completely trashed by taking 2 tbsp of starch each day, which I thought was zero carbs, but actually has 20 carbs just in those 2 tbsp, which doubled my daily carbs and kept me out of ketosis.

    • I contacted them to ask the same question and they stated that it is Not a resistant starch. Good that you mentioned this or I would have been eating that stuff without knowing that it is not beneficial. I did buy some Wedo Green banana flour which is a resistant starch. Thanks

      • I just emailed them too and rec’d a reply this evening…

        “Thank you for reaching out to us. Our Potato Starch is not a resistant starch. The process of removing the starch component from the potato eliminates any resistant starch benefits.

        Please feel free to contact me if you have any more questions and have a wonderful day.”
        Now I used some and liked the thickening it gave to my protein drink, but the carbs… I don’t like it that much!

        I just purchased some hi maize RS from amazon (I have no philosophical issues with GMO items) – I’ll see how that goes. Next step is actual banana flour, but that’s more expensive than the hi maize…

        As to why I don’t just eat potatoes… I’m not all that keen on cold potatoes, and I travel almost every week for work. I just can’t see getting that easily when on the road. Since I do work out with free weights and have a (chocolate) protein shake after working out, it just is easier that way.

        • It’s true that if you ask Bob’s Red Mill if their potato starch contains RS, they will say it does not. We aren’t exactly sure why this is the case but I wouldn’t write-off Bob’s potato starch just yet.

          People are sending off Bob’s potato starch and getting the RS levels tested. A good example is from the University of Michigan’s recent study:


          “During the intervention phase, raw unmodified potato starch (Bob’s Red Mill, Milwaukie, OR) was gradually added to their diet (day 1—12 g, day 2—24 g, day 3—48 g; Fig. 1). This potato starch contains approximately 50 % resistant starch (type 2) by weight. ”

          So, we know that Bob’s is saying there is no RS in their product, and there is some speculation as to why they are saying that. However, we still feel comfortable recommending it.

          We are definitely looking into this issue and hopefully we will clear up any confusion with an upcoming blog post.

        • Seems that Bob’s Red Mill’s employees are confused about their own product. I emailed Tim Steele, author of the Potato Hack and an authority on RS, about this, and here is his reply:

          “Hi Chris – I have heard this as well, that Bob’s Red Mill is telling people that their potato starch does not contain RS. I have three thoughts:
          1. Bob’s does not want to be in the RS/health supplement arena, so they are intentionally spreading a falsehood,
          2. Bob’s customer service people do not know that their product is high in RS, and give the wrong information,
          3. Someone is spreading “false news” so people use a more expensive product.

          I am 100% convinced that Bob’s Red Mill Unmodified Potato Starch, and all other products labeled “unmodified potato starch” are good sources of RS. Bob’s Red Mill does not make the starch, they buy it from distributors. All potato starch is made in a similar fashion, easily Googled, and it results in a product that contains uncooked potato starch granules. Depending on test methods used, the percentage of RS in a sample of potato starch is 50-75%. In fact, a sachet of unmodified potato starch is provided with the test kit for testing RS content in order to calibrate the process. There is no other native starch with a higher RS content than potato starch, so it makes a good control for the “span” of the test method, known as AOAC2002.02.

          I have been helping people create prebiotic blends for a couple years, several have sent samples of various unmodified potato starches to Medallion Test Labs. All received a certification that the potato starch is in the 55-65% range, I know personally of one sample of Bob’s Red Mill was tested that was 64% RS. Several samples of arrowroot starch, however, have been shown to contain ~2% RS. WeDo GlutenFree Banana Flour is about 45%, and Hi-Maize corn starch is 45-55%.

          UMich did a nice study on RS2 using Bob’s Red Mill Unmodified Potato Starch last summer, had it tested, and found it to be ~50%. I’m not sure which lab, or if they tried testing it themselves, but at any rate, Bob’s PS worked beautifully in their study.

          Variable responses of human microbiomes to dietary supplementation with resistant starch (https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-016-0178-x)

          “Participants consumed their habitual diet throughout the study period. During the intervention phase, raw unmodified potato starch (Bob’s Red Mill, Milwaukie, OR) was gradually added to their diet (day 1—12 g, day 2—24 g, day 3—48 g; Fig. 1). This potato starch contains approximately 50 % resistant starch (type 2) by weight.”

          “Our data show that dietary supplementation with RS type 2 as unmodified potato starch increases fecal butyrate concentration, but with remarkable inter-individual variation.”

          For $145, anyone can get some starch tested at Medallion labs, and several other labs that test this sort of thing. I’m surprised Bob’s Red Mill does not regularly test and label, but then they would be selling a supplement and not a cooking ingredient. Soon, you will be seeing products with an official RS content label, I have no doubt.

          Seems funny to be re-hashing this so many years later, but looking through my notes, I found this, Measurement of resistant starch by enzymatic digestion in starch and selected plant materials: Collaborative study, this was the original experiment to develop AOAC2002.02 for RS testing. They sent samples of various starches to 37 different test labs, Table 2 shows the range of results for potato starch (~45-70%, mean 63%). The potato starch used was a standard commercial brand (Avebe Potato Starch, NL).

          Interestingly, Bob’s Red Mill told one person that their potato starch was of “Dutch origin,” one website listed it of “Malaysian origin.” My guess is that they buy it from the lowest bidder in huge bulk. On the open market, this product is traded as “native potato starch” meaning the granules are intact. Otherwise, it’s sold as “modified potato starch.”

          Hopefully this clarifies the issue.

          • I bought a Walmart blood glucose meter, strips , lancets and “gun” for about $30, as suggsted by Dr. William Davis. After eating a medium thinly sliced Yukon Gold potato with a little salt my blood glucose was down 2 mg/dl at 45 min. after ingestion. An earlier self test with pressure cooked and fridge (2 days) cooled potato then re-heated for 123 sec. in the microwave showed a jump to 175 mg/dl— a failed RS test.
            I have yet to test Bob’s Red Mill potato starch although i have gone through 2 bags. I just ate the last and biggest potato in the bag.

            • Was that first potato hot or cold?

              I’ll be interested in hearing about your experience with Bob’s. I toss 3/4 scoop in to my chocolate protein drink every day. If nothing else, it’s good for the microbiome.

            • As I understand it from reading the initial research reports, if you re-heat the potato, (or rice) the starch converts back and is no longer resistant. You have to consume it cold. Potato salad, anyone?

        • I have heard several times that hi-maize is a GMO. Biology and genetics can be mysterious but the language used to catagorize GMO from non-GMO is fairly straightforward to someone who has studied it. Hi-maize is not a GMO. It’s come from a variety of corn a plant breeder of humble origins found in the 1950s when innovations and discoveries was done by family businesses. He loved Science, was good at recognizing natural variation that had potential economic value. The gene in hi-maize is a naturally occurring phenomenon that strangely is a gene that works together with the gene in sweet corn to make normal starch. I have developed RS maize. Why? To demonstrate the value of genetic diversity which is a resource that slowly is being lost. I found the genes to recreate Hi-maize by looking at hundreds of open-pollinated populations of corn from Latin America. The gene came from a village in Southern Guatemala. The variety is hundreds perhaps thousands of years old. Many studies on the nature of the starch and numerous clinical studies suggest that it is effective in improving gut health. It was my hope that people would recognize the importance of preserving agricultural biodiversity. Perhaps as a result I have further jeopardized this goal. Is Amylomaize the best. I don’t know. At least I developed it, worked with others to study it to better understand how it might help people so they have information to make a choice. Please spend some time reading up on what GMOs are. I would be glad to provide more details. What concerns me is that there is little money spent on stable food crops to address the erosion of genetic diversity. Just think how much worse it is with bannanas or potatoes. I don’t mean to ridicule those that find this complicated. I struggle with technology like others. In fact, I have spent almost a week trying to reboot my Dell laptop. Bet some of you could do that in there sleep. Thanks for your time. Keep reporting on your adventures with RS, no matter what the source.

          • I was so glad to hear this comment- I had just purchased 1 lb. bag to see how it works in losing weight and if it will still be resistant if used in baking and cooking and the amount to use. I tasted it first and then put close to a tablespoon in my 2 cups of warmed coffee each at 8am. It is now noon and I have no hunger pangs or cravings. I am totally amazed since it is my first day.My cravings are my downfall especially for chocolate! Is there a good cookbook to use? I ordered one but it hardly uses hi-maize resistant starch flour. Most of the foods are very high carb but uses the above mentioned foods & techniques in it’s recipes.It’s only my first day and I’ll have to see how weight loss goes but if I’m not hungry I would hope & suspect I would have weight loss since it has minimal calories and I am not eating as much. I wish it was organic because I don’t want residual pesticides in what I eat! Does anyone know of an organic hi-maize resistant starch flour?I am tech-illiterate too in spite of a health science background! Thanks again for your post!

  12. I’m a little surprised to find a recommendation to eat potato starch on Chris’s site, as I thought he primarily advocated a Paleo diet. Is RS available from non-grain and non-legume sources?

    • Potatoes are not a legume or a grain; they are a starchy vegetable. Anthropologists agree that tubers (starchy vegetables were a part of the Paleolithic diet.