2017 Resistant Starch Review

Throughout my book, The Potato Hack: Weight Loss Simplified, I discuss a special type of fiber known as resistant starch (RS). I’ve written loads about this amazing prebiotic here in The Potato Hack Chronicles, as have hundreds of other bloggers and researchers…just Google “resistant starch,” and you’ll find a treasure trove of articles and scientific papers.

Please keep in mind as you read on that an all-potato diet contains more resistant starch than any other diet you could possibly eat, and all from real foods…no supplements needed!

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Occasionally researchers will look at mounds of data on a particular topic and write a review paper. In January 2017, the British Nutrition Foundation released a nutrition bulletin for food producers and medical professionals. This paper, “Health effects of resistant starch (Lockyer and Nugent, 2017),” is a review of hundreds of research papers written over the past 20+ years. In this blog post, I will “review the review” and point out some interesting findings. Let’s start with Lockyer and Nugent’s bottom line. Please read this carefully:

There may be a lot still to be discovered in terms of the health benefits of RS. At present, most RS research relates to RS2. A wider spread of evidence relating to all RS types, via the testing of whole foods, would be useful in informing innovation, the selection of grains/varieties of RS-rich foods and perhaps in future, a recommended intake value for RS.

From the 2017 review, Health effects of resistant starch.

The paper is divided into sections based on current research, please click and review if you have time. Find here a description of the sections, and the “key points” noted by the authors, but first a short video released by the British Nutrition Foundation:

Section 1. Resistant Starch Overview:

  • Starch types;
  • Methods of analysis;
  • Challenges in developing high RS foods;
  • Safety;
  • Labeling and health claims.

Key Points 1 –

  • RS is a type of dietary fibre.
  • It passes through the small intestine intact and is then fermented in the large intestine, producing SCFAs.
  • RS provides ˜2 kcal/g.
  • There are five different types of RS (RS1, RS2, RS3, RS4 and RS5).
  • RS is present in grain products, seeds, pulses, bananas, potatoes and in commercially purified forms, which can be added to food products.
  • RS intake is estimated to be around 3 g/day in the UK and is likely to be similar in other countries with Western-style diets.

Section 2. Resistant starch and colonic health, studies reviewed:

  • Short-chain fatty acid production;
  • Influence of resistant starch on gut bacteria and the microbiome;
  • Pre- and probiotics;
  • Colon cancer;
  • Conditions associated with disturbances in gastrointestinal function;
  • Oral rehydration solutions.

Key Points 2 –

  • RS increases the production of SCFAs in the gut but there appears to be significant inter-individual variation in responses.
  • RS modulates the composition of gut microbiota, specifically those involved in amylose breakdown and butyrate and methane production, but responses are variable and health implications remain to be elucidated.
  • There is some evidence that RS can counteract the detrimental effects of high red meat intake on colorectal cancer risk.
  • Emerging evidence suggests a role of RS as an ingredient in oral rehydration solutions.

Section 3. Role of resistant starch in metabolic responses – lipid and glucose metabolism, insulin resistance and prevention of cardiovascular disease, type 2 diabetes and metabolic syndrome, studies reviewed:

  • Influence of resistant starch on other markers of metabolic health;
  • Proposed mechanisms/sites of action of resistant starch.

rs-mechanisms

Key Points 3 –

  • It is well accepted that postprandial glycaemic responses to RS are reduced compared with digestible carbohydrates.
  • In the EU, there is an approved health claim that baked products containing at least 14% RS in place of digestible starch reduce postprandial glycaemia.
  • There may be synergism between RS and other fibre types in reducing glycaemic responses.
  • More long-term studies are required to fully ascertain the effect of RS consumption on plasma lipids.

Section 4. Resistant starch and appetite regulation, studies reviewed:

  • Dietary fibre and satiety;
  • Resistant starch, satiety and acute energy intake;
  • Resistant starch and bodyweight;
  • Other health benefits of resistant starch.

Key Points 4 –

  • There is some evidence that RS can decrease appetite and short-term food intake.
  • Potential mechanisms include an increase in the release of gut hormones that promote feelings of satiety, stimulated by SCFAs.
  • There is little evidence that RS can decrease adiposity in humans.
  • RS may have a role in treating chronic kidney disease.

 

Conclusions –

Theirs (emphasis mine):

…current evidence points towards RS as a dietary component with several potential health benefits and no harmful effects, besides possible gastrointestinal symptoms in some individuals at high intakes.

…wealth of evidence linking RS to reduced postprandial glycaemic responses has resulted in an EU-approved health claim.

It is clear from animal and in vitro studies that RS modulates many outcomes related to gut health but there is difficulty in translating this to humans

There is evidence that RS can increase the production of SCFAs in the human gut but there appears to be a significant degree of variability in response to RS intervention, most likely influenced by differing gut microbial compositions between individuals, habitual intake, RS type and presence or absence of other RS and other fibre types.

There is good evidence that RS influences gut microbial communities involved in amylose breakdown and butyrate and methane production, but there is a significant variability in responses.

There is some evidence that RS can positively influence satiety and short-term food intake and plausible biological mechanisms have been demonstrated, but results have not been consistent.

Mine:

This review pointed out several of the inconsistencies I’ve been talking about for many years, that each individual will react a bit differently when increasing the RS in their diet. But besides some unwanted gas, there is only good to come of increasing RS in your diet.

This review pointed out poor study design in many RS studies, ie. too short, no acclimation period, or the wrong type of starch was used.

This review demonstrated that large benefits of RS come from RS2 in supplemental form. While it is great to think we can get all of our fiber needs from the foods we eat, this is not always the case. This does not suggest, however, that we should rely on fiber and RS supplements for all of our needs. My advice has been, and always will be, to eat lots of high fiber, high RS foods and to take a fiber/RS supplement if you so desire.

Still to be determined: Exactly how much and what type of RS is best for inclusion in the human diet. Until a governing agency tells us exactly what we need, we are on our own here.

Bonus Material:

For an amazing, in-depth review of resistant starches, please see, Resistant Starch Sources, Applications, and Health Benefits (2013).

Food Sources of Resistant Starch & The Potato Hack

A 2008 study, Resistant starch intakes in the US, found that most Americans ingest about 5 grams of RS per day. This RS is mostly in the form of RS3 from bread, pasta, and other wheat products. Other sources are from potato chips, beans, and rice. Studies find that the benefits of RS are seen at much higher intakes of 20-40g per day.

The Potato Hack is a short-term intervention where one eats nothing but potatoes for several days in a row. Eating 3 pounds of potatoes provides 30-40g of RS. If one cooks and cools their potatoes, that number doubles!

Unripe bananas (still mostly green) contain about 15g of RS2 per medium banana. A 1/3 pound (150g) raw potato contains about 20g of RS2. These two food items can be eaten daily as a source of RS2.

Supplemental Sources of Resistant Starch

While it’s possible to get 20-40g of RS per day from your food, one would need to consume several pounds of bread or pasta prepared to be high in RS or several pounds of cooked then cooled potatoes, beans, or rice. Researchers use concentrated forms of RS2 when studying its effects on humans or animals. This type of RS is easily and cheaply purchased, for instance:

These three cooking ingredients may be used to supplement RS, the recommended dosage is 1-4TBS per day.

Parting shots

I’ll be reviewing the new studies that come out this year and writing about them frequently. I think sometimes we tend to make things more difficult than they need to be, so keep in mind that if you just take a spoonful or two of one of the RS sources mentioned above, you’ll be getting double or triple the RS that the average person gets. It’s my belief that this should be done long term. RS and “fiber” are two separate things, I believe that newer research will show that we have a requirement for raw starch granules to keep our guts in tip-top shape, and we also need other types of fibers to keep things moving, reduce cholesterol, etc.

Tim Steele

18 Comments on “2017 Resistant Starch Review”

  1. Stuart C January 16, 2017 at 1:01 pm #

    It appears that more attention gets given to RS2 & RS3 and less to other fiber types like FOS, GOS etc. Do you know why this is the case?

    Also, I know this blog focuses on potatos but I’d be interested to read your knowledge on rice, beans and various grains.

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    • Tim Steele January 16, 2017 at 2:47 pm #

      I think it’s just because the other finer types have been well-studies since the 70’s and this RS thing is just now coming to light. At first, everyone just lumped RS together with fiber, but now we are seeing that different fibers have different functions, and RS specifically seems to act in concert with our immune system moreso than the other fiber types.

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      • Stuart C January 17, 2017 at 2:36 am #

        I’ve been eating 30g/day of fiber. 15g RS3 and 15g inulin (mainly from jerusalem artichokes).
        I wonder if I should try to shift the balance more towards RS3 or add some RS2 into the mix.

        I guess as the article says, we don’t know the best amount or ratios.

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        • Tim Steele January 17, 2017 at 8:32 am #

          It’s all going to depend on how your body reacts, really. I am convinced that RS2 possesses immune stimulating properties that the other fibers do not, so if anything, I’d add in some RS2.

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  2. Jo tB January 17, 2017 at 7:37 am #

    From reading the review article, can I take it that barley has become the new RS kid on the block?

    barley that contains RS in addition to other fibre types (e.g. NSP).
    has focused on a novel high-amylose barley variety (Himalaya 292) rich in RS
    Ninety-one per cent higher faecal excretion of butyrate and 57% higher faecal total SCFA excretion were reported compared with the refined cereal control

    A good product to add to the RS-mix which Wilbur recommends?

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    • Tim Steele January 17, 2017 at 8:30 am #

      I’m certain there is an arms race going on now to develop high-RS grains that will meet the definition of “high in RS.” But, I’ve always liked buckwheat and think it’s a great food item, even if it’s just plain old barley and not a high-amylose variety. Hi-Maize was the first grain specifically bred to be high in amylose and RS, now others are trying to get in on the game…a good thing!

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  3. Shameer Mulji January 17, 2017 at 2:59 pm #

    “Eating 3 pounds of potatoes provides 30-40g of RS. If one cooks and cools their potatoes, that number doubles!”

    Is that correct? On page 206 in your book is states that if you boil, cool, then reheat potatoes, 1lb of potatoes will yield approximately 12g of RS2. For 3lbs, that’s 36g of RS2.

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    • Tim Steele January 17, 2017 at 3:24 pm #

      You guys are getting too smart for me! My point really is just that cooking and cooling greatly increases the RS content. Since I wrote the book, there have been a few better papers on how much RS is in potatoes. Here’s a blog I did about one of the most recent analyses of RS: https://potatohack.com/2016/12/06/resistant-starch-content-of-potatoes/

      I find myself generally saying now that potatoes cooked a bit firm will contain about 12g per pound of RS, and 25g when cooked and cooled. But this is just a rough guesstimate as each batch would have to be tested to ascertain the exact quantities.

      Tim

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  4. Dan January 17, 2017 at 8:08 pm #

    Not wanting to stir the pot too much, because I like and follow all your blogs and bought your book Tim. I’ve also done multiple weeks of the potato hack with good success.

    However today I was googling and came across info that says maybe be careful about too much RS2 from supplements because it overshadows other probiotics in the gut and causes trouble. These were articles from last year (maybe you even contributed so some ) and maybe there is new info now. But it started me to wonder if I should EVER use supplements with isolated potato starch or hi maize corn or even banana flour, as opposed to simply eating real foods. Here are the links:

    http://drbganimalpharm.blogspot.com/2014/06/contupdate-2-rs2-and-rs3-are-not.html

    https://www.thepaleomom.com/resistant-starch-its-not-all-sunshine-and-roses/

    Again, only asking for your expert opinion, but just wondering if they have a point. Is it possible that too much RS2 from potatoes and isolated potato starch from sources such as Bobs, could displace other good probiotic gut bacteria?

    Like

    • Tim Steele January 17, 2017 at 9:02 pm #

      Maybe it would be better to ask the authors of the two blogs you mention if they have read the 2017 review, and looked at all of the ongoing clinical trials using RS2 and ask if they would like to reconsider their stance. Then get back to me.

      Here’s a list of about 40 clinical trials using RS2, maybe someone should send them those two blogs to make sure they are aware of the dangers, lol.

      https://clinicaltrials.gov/ct2/results?term=%22resistant+Starch%22&Search=Search

      Read the comments of the “paleomom” blog for a good laugh.

      I think that if someone were to eat a fiber-free diey=t and try to get all the prebiotics from potato starch or Hi-Maize, it would be less than optimal, but not dangerous. But to include some RS2 from Hi-Maize, PS, or GBF is a great thing, as the 2017 review so succinctly points out.

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      • Tim Steele January 17, 2017 at 9:05 pm #

        This is one of the clinical trials in the list, can’t wait to see the results! This clinical trial is being conducted by Manitoba Starch, I assume they are doing it so that they can start selling their potato starch as a health suplement instead of a cooking ingredient.

        “The purpose of this clinical trial is to study the effects of potato resistant starch on the microbiota (microorganisms or bacteria) and short chain fatty acids levels of the gut. Levels will be measured and compared between elderly adults and in pre-elderly, adults from the general public. A correlation between the use of potato resistant starch and specific clinical and quality of life endpoints between elderly adults and in pre-elderly, adults from the general public will be studied.

        Hypothesis 1: The investigator hypothesizes that the microbiome in elderly adults (≥70 years) is less diverse and more prone to imbalance compared to adults (30-50 years) from the general population and that this imbalance of the gut microflora in the elderly adults is partially related to inadequate RS in their diet.

        Hypothesis 2: The investigator hypothesizes that ingestion of potato resistant starch of food grade quality (MSPrebiotic) will stabilize the gut microbiome (i.e. high Firmicutes/Bacteroides ratio)in LTC residents (i.e. similar to that of adults from the general population), thereby improving gut health and reducing the risk of diarrhea and/or gut infection.”

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  5. Dan January 17, 2017 at 9:34 pm #

    Tim, You are right, I should ask those other blogs first. Not knocking your info, which is huge and very welcome. I’ll do more research on my own next time before I chirp up here. Thanks.

    Like

  6. Jo tB January 18, 2017 at 12:35 am #

    From what I have noticed in studies is that they use one RS2 sort only, i.e. potato starch, or Hi-Maize cornstarch, or green banana flour. I am assuming that if you use more than one source, too many confounding factors enter, which will muddy the results.

    However, we don’t exclusively eat one RS source as our gut bacteria are specialists as well, some are dairy eaters, others are meat eaters, etc. So if we want a varied gut biome, we have to eat various sources of RS. Our ancestors did, so should we.

    At the height of the Potato Starch hype, I was always hesitant of putting all my eggs in one basket, so I always looked for as many sources of RS as I could find, and used them all.

    Like

  7. Bertold January 20, 2017 at 3:24 pm #

    I have been using a mixture of Hi-M 32%, PS 49%, GBF 12% & 7% of Psyllium. In a bit of goat kefir, 2 TBS in the morning and 2 TBS at night. Other than a bit of increase in gas have not noticed any bad effects, and I belong to that group of “elderly people” (88) with supposedly less healthy microbiome. However I also eat a plate of raw radish, red pepper, cucumber, celery and cherry tomatoes, as well as a plate of mixed greens salad Whatever potatoes we eat are always steamed and cooled in the fridge the night before consumption. I have lost weight with every potato hack I have ever done (7) but unfortunately I always regain most weight until I reach what appears to be my set-point of
    168 lbs on a 5′ 11″ frame. Can anyone detect anything I am doing wrong ? I would really stay at around 160lbs. So do I aim for my next potato hack ? For those interested, I am doing a daily excercise called “The 5 Tibetans” so not totally w/o movement. Walks are governed by temperature in our cold Canadian climate.

    Like

    • Tim Steele January 20, 2017 at 4:55 pm #

      Sounds like you are doing great! I assume you are a man. If so, 168 lbs is not bad at all. But, it makes me wonder, perhaps what you see on the potato hack is an overall decrease in inflammation, and when you return to your normal diet, it returns. Does the weight reappear quickly, or does it take several weeks?

      Anyway, what you might consider is doing 3 days of potatoes-only, then reintroduce regular eating slowly. Like potatoes until dinner, and then more potatoes for dinner, plus some of your regular foods.

      Could you give us a list of what you normally eat? Roughly.

      Like

      • Bertold January 27, 2017 at 3:37 pm #

        Yes, I’m a man. How I originally got on to all this, was some ugly belly fat. I weighed around 178-179lbs. And as I am very borderline in jeopardy of diabetes, I wanted to get rid of the fat – see Dr. Ron Taylor’s work of University of New Castle UK – to regain sensitivity of insulin.

        You have also stated that RS via butyrate will assist in bringing back insulin sensitivity. I believe I am on the right track. I am sure inflammation is down too.

        I do not eat anything containing sugar any more, no white flour, white bread or white pasta. I do eat cooled off parboiled rice to get some RS. The only bread I eat is something called “Mestemacher” a kind of pumpernickel. Max one slice per day. I try to be low on carbs. And I always have either a salad or a plate of raw veggies with every meal.

        My fasting BG is between 5.5 mmol/dcl and 7.2, depending on what I eat. When on the Potato Hack, I am scoring usually low in the hi 5’s.

        The weight btw comes back over a period of ten days or so, but slowly. And it always hangs around 168. But I do have a scotch or two on the weekend.

        I am very grateful to you Tim for all your work, which has been helping me to steer clear of the dark side of diabetes.

        Like

Trackbacks/Pingbacks

  1. Resistant Starch and Heart Disease | The Potato Hack Chronicle - February 2, 2017

    […] we think of resistant starch (RS) as protective, there’s a new paper out that says RS may cause cardiovascular disease! […]

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