Sunday, October 25, 2015

New Resistant Starch Research

On a lark, I searched PubMed this morning for new RS articles.  Looks like scientists keep finding no end of ways to study this crazy little granule!

Picture Credit

The newest studies out on RS (Oct/Nov 2015):

1. Unique Organization of Extracellular Amylases into Amylosomes in the Resistant Starch-Utilizing Human Colonic Firmicutes Bacterium Ruminococcus bromii.

Recent evidence indicates that certain human colonic bacteria play keystone roles in degrading nondigestible substrates, with the dominant but little-studied species Ruminococcus bromii displaying an exceptional ability to degrade dietary resistant starches (i.e., dietary starches that escape digestion by host enzymes in the upper gastrointestinal tract because of protection provided by other polymers, particle structure, retrogradation, or chemical cross-linking). In this report, we reveal the unique organization of the amylolytic enzyme system of R. bromii that involves cohesin-dockerin interactions between component proteins. While dockerins and cohesins are fundamental to the organization of cellulosomal enzyme systems of cellulolytic ruminococci, their contribution to organization of amylases has not previously been recognized and may help to explain the starch-degrading abilities of R. bromii.

2. Resistant starches for the management of metabolic diseases.

Recent clinical trials and animal studies indicate that resistant starches may be beneficial therapeutic tools for the management of metabolic diseases. The purpose of this review is to summarize these findings and discuss the established and proposed mechanisms by which resistant starches exert their benefits. We also examine open questions regarding how resistant starches improve metabolism and propose future research directions for the field.
Data from both humans and animal models clearly support a role for resistant starches in improving a variety of metabolic features; however, discrepancies do exist regarding specific effects. Concomitant improvements in both insulin levels and body fat depots are often reported in rodents fed resistant starches, whereas resistant starch feeding in humans improves insulin sensitivity without having a major impact on fat mass. These differences could be explained by the coexistence of several mechanisms (both gut microbiota-dependent and gut microbiota-independent) underpinning the metabolic benefits of resistant starches.
Together, the studies presented in this review offer new insights into the potential pathways by which resistant starches enhance metabolic health, including modulation of the gut microbiota, gut peptides, circulating inflammatory mediators, innate immune cells, and the bile acid cycle.

3. Improving healthspan via changes in gut microbiota and fermentation.

Dietary resistant starch impact on intestinal microbiome and improving healthspan is the topic of this review. In the elderly population, dietary fiber intake is lower than recommended. Dietary resistant starch as a source of fiber produces a profound change in gut microbiota and fermentation in animal models of aging. Dietary resistant starch has the potential for improving healthspan in the elderly through multiple mechanisms as follows: (1) enhancing gut microbiota profile and production of short-chain fatty acids, (2) improving gut barrier function, (3) increasing gut peptides that are important in glucose homeostasis and lipid metabolism, and (4) mimicking many of the effects of caloric restriction including upregulation of genes involved in xenobiotic metabolism.  

4. Influences of exogenous probiotics and tea polyphenols on the production of three acids during the simulated colonic fermentation of maize resistant starch.

In the present study, influences of nine probiotics and tea polyphenols on the production of acetic, butyric, and lactic acid from simulated colonic fermentation of maize resistant starch (RS) were investigated. RS was fermented by fecal extracts of healthy adults at 12 g L(-1) and 37 °C for 18-48 h in the presence and absence of exogenous probiotics and tea polyphenols. The added probiotics increased acetic and butyric acid production by 25-216 %. Eubacterium faecalis, Lactobacillus acidophilus, L. casei, and L. helveticus increased lactic acid production by 7-58 %; however, other probiotics decreased lactic acid production. Tea polyphenols facilitated lactic acid production but inhibited acetic and butyric acid production clearly. More importantly, the added probiotics weakened the inhibitory effects of tea polyphenols on the two acids, enhancing acetic and butyric acid production by 152-641 and 825-1,777 %, respectively. It is concluded that both probiotics and tea polyphenols have different impacts on the production of acetic, butyric and lactic acid during the colonic fermentation of RS. The impacts of other probiotics and food components on the colonic fermentation of RS and other dietary fibers should be investigated in future study to clarify their possible interactions. 

5. The Glycemic Potential of White and Red Rice Affected by Oil Type and Time of Addition.

 Limited research exists on how different oil types and time of addition affect starch digestibility of rice. This study aimed to assess the starch digestibility of white and red rice prepared with 2 oil types: vegetable oil (unsaturated fat) and ghee (clarified butter, saturated fat) added at 3 different time points during the cooking process ("before": frying raw rice in oil before boiling, "during": adding oil during boiling, and "after": stir-frying cooked rice in oil). Red rice produced a slower digestion rate than white rice. White rice digestibility was not affected by oil type, but was affected by addition time of oil. Adding oil "after" (stir-frying) to white or red rice resulted in higher slowly digestible starch. Red rice cooked using ghee showed the lowest amount of glucose release during in vitro digestion. The addition of ghee "during" (that is boiling with ghee) or "before" (that is frying rice raw with ghee then boiling) cooking showed potential for attenuating the postprandial glycemic response and increasing resistant starch content. This is the first report to show healthier ways of preparing rice. White rice with oil added "after" (stir-fried) may provide a source of sustained glucose and stabilize blood glucose levels. Boiling red rice with ghee or cooking red rice with ghee pilaf-style may provide beneficial effects on postprandial blood glucose and insulin concentrations, and improve colonic health. The encouraging results of the present study justify extending it to an in vivo investigation to conclusively determine the effect of time of addition of fat when rice is cooked on blood glucose homeostasis.

I'll leave my thoughts on these for the comments...what do you guys think?



  1. Thanks for this article, looking forward to digesting it after my potato lunch :)
    Last night my husband made pasta (we had not had it so long due to the processed nature of it)...but this one is different: Dreamfields
    ingredients: enriched semolina, inulin, wheat gluten, xanthan gum and pectin

    tasted like regular pasta....but with after effects - not to be too graphic - large softer stools...but not loose ones.
    I realize a couple ingredients are questionable: the enrichment and the gluten)....but as an occasional substitute for regular pasta - your thoughts?

    1. Semolina is just another word for wheat. Enriched wheat at that. We have been getting
      Ancient Harvest Quinoa Spaghetti when we get the urge for pasta. They make elbow mac, too! Ingredients: Organic Corn Flour and Organic Quinoa Flour..that's all. Good stuff, but easy to overcook.

    2. I've never been happy with unusual pastas. Corn flour and quinoa pasta? Shudder. Give me good stuff!

      I started with a lifetime of pasta abuse. Couldn't get enough. Then I fixed my gut. Now I can eat pasta. I just eat a lot less. There's no struggle or willpower. We're probably talking one or two servings per week.

      As such, I eat the good stuff, but not fortified. (Enriched in baking usually means with added oil, so I use fortified to refer to added iron and such.). I've tried Dreamfields before. It's ok, but I'd never eat it now if it is fortified. I never eat (shudder) quinoa or corn pasta, although I've tried them.

      I've been really happy with

      It has several shapes available. Generally speaking, organic pasta is not fortified.

  2. I've tried the quinoa pasta before...yes, it needs to be al dente...agree about the wheat..I found it novel that they chose to blend the inulin, pectin and gum in with the wheat flour to change the usual nutritional (metabolic?) profile of pasta and yet the flavor and texture was amazingly similar to regular wheat pasta. This triggered me to consider whether there isn't an opportunity waiting to create some kind of healthier flour (what grain or bean or plant?) and fiber blended pasta that mimicks the flavor and texture of traditional Italian pasta. Just a thought. It must have been all that garlic and all those tomatoes that saved the Italians :0

    1. Also, true Italians use pasta as a side, not the heaps that we North Americans use. And interestingly, in my husband's family at least, salad is served at the end of the meal. I've always wondered what sort of difference that makes to the digestion.

    2. I have always eaten my salad at the end of the meal. As a child and an adult.

    3. " opportunity waiting to create some kind of healthier flour ..."

      ha! Looks like it's in the works.

      "Arcadia Biosciences, Inc. (NASDAQ:RKDA), an agricultural technology company, announced that the United States Patent and Trademark Office has granted the company US Patent No. 9,150,839, entitled " Wheat with Increased Resistant Starch Levels." The patent covers Arcadia's non-genetically modified Resistant Starch (RS) Wheat lines.
      Arcadia's RS Wheat was developed using the company's proprietary wheat genetic diversity library, an extensive and exclusive resource of wheat lines with high-density variations in genetic composition and gene function. The RS Wheat project was funded in part by a grant from the US National Institutes for Health (NIH) and is currently in Phase 4 of Arcadia's development pipeline.

      Resistant starch is a form of dietary fiber that is digested more slowly than regular starch. Slower digestion results in a slower release of glucose into the bloodstream, so food products made with RS Wheat have a lower glycemic index. Resistant starch also is fermented in the lower intestine to provide additional colon health benefits.
      Compared to conventional wheat varieties, which have very low levels of resistant starch, Arcadia's RS Wheat has significantly higher levels of total dietary fiber in both whole grain flour and especially refined white flour. Studies have linked resistant starch to improved insulin sensitivity, lower blood glucose levels, and increased satiety, benefitting people with diabetes, pre-diabetes and obesity.
      "Because wheat is the world's largest cultivated crop, it's a key focus for the health-promoting benefits of resistant starch," said Eric Rey, president and CEO of Arcadia. "RS Wheat creates the potential for wheat-based whole foods like pasta, bread and other baked goods with higher fiber and fewer additives. Foods like these may taste and perform like those made with refined wheat, but have significant additional health benefits. This could make a great contribution to global health, and represents a major financial opportunity for Arcadia."
      The global market for whole grain and high fiber foods is projected to reach $29.5 billion by 2020, driven by growing consumer focus on health and well-being, and increasing awareness of the benefits of a whole grain and fiber rich diet, according to a report from Global Industry Analysts, Inc. The USDA recommends a total dietary fiber intake of 25-38 grams a day, but Americans typically only consume a daily average of 16 grams of fiber. In addition, fiber consumption is below recommended amounts in many countries despite the World Health Organization's recommendation of at least 25 grams of fiber a day."

    4. We ate 'salad' as part of the meal. Soup first, then the whole rest of it all.

    5. Tim, I'm tired of the WHO. They majorly dropped the ball with Ebola and forever come out with all sorts of pontificating crap. Like today it was all about how consuming even 50 grams of bacon increases risk of colorectal cancer. Well, I guess all the bacon noshing paleo dudes are in BIG trouble. They'll watch the news and the sound of bacon being spat out will be heard across the land.

      There's more to colorectal cancer than freaking bacon. What does the WHO want? Turn everyone into a sugar eschewing vegan?

    6. Yeah, I have been reading these articles all day. It seems their threshold is about 1 pound per week of cured meats. I doubt I eat a pound a month. Bacon and salami are tasty, but definitely don't have a prominent place in my diet.

      You know what negates the damage caused by cured and red meats, right? Gut flora!

      Eat your fiber rich, plant-filled diet and enjoy a few rashers now and then. I will admit when I first "went paleo" I would eat a pound of bacon in one meal. Silly.

    7. Gab, you are not the only one tired of WHO.
      "Here’s the thing: These classifications are based on strength of evidence not degree of risk.

      Two risk factors could be slotted in the same category if one tripled the risk of cancer and the other increased it by a small fraction. They could also be classified similarly even if one causes many more types of cancers than the other, if it affects a greater swath of the population, and if it actually causes more cancers.

      So these classifications are not meant to convey how dangerous something is, just how certain we are that something is dangerous.

      But they’re presented with language that completely obfuscates that distinction.

      Perhaps we need a separate classification scheme for scientific organizations that are “confusogenic to humans.”

    8. You might be interested in a point style summary of the recommendation's deficiencies, including things such as analysis design and the usual association vs. causation -

    9. Very interesting about Arcadia. My only concern is whether the resistant starch will survive the baking process.

  3. Hi Tim,
    Thanks for keeping us appraised of emerging research.
    I'd like to add that I don't think linking to is a good idea for your site (where many of us turn for accurate information), on 2 counts.
    First, sweet potato is a poor source of resistant starch, so the diagram is misleading.
    Second, reading the description of RS3 in that post - "TYPE 3 are foods that become starchy after cooking. This includes sweet potatoes, rice, yams and some whole grain breads."
    This is simply incorrect and can lead to unnecessary confusion regarding the formation of RS3.
    Thanks for considering this, I know this is your site and you can post whatever you'd like.

    1. You are absolutely right! Lazy me, I just Googled "Resistant Starch Images" and used the first one I found. This one better? Funny, though, I was just looking around for other images...there is still lots of misinformation out there. I see my work is not yet complete!

  4. One person at a time, you can and will influence and educate, just look at your comments section! Yes, this image is simple and informative :)

  5. The WHO and bacon is the talk of the town in Australia as well. It got repeated on all the morning talk shows plus news bulletins. Grrrr!!

    Jo tB

  6. Stumbled across this today:

    "Addition of dietary fiber sources to shakes reduces postprandial glycemia
    and alters food intake"

    Couldn't see it posted elsewhere


    1. Is this the first fecal transplant pill? I'd prefer to snort lol

  8. Off topic, but does popcorn contain a RS? Heating popcorn causes the water inside to boil, and the kernel to explode...then it cools. I'm wondering about eating it cold hours later.

  9. Off topic, but does popcorn contain a RS? Heating popcorn causes the water inside to boil, and the kernel to explode...then it cools. I'm wondering about eating it cold hours later.

    1. I love popcorn, but I don't think there is much RS in it. Other fibers, but not RS. I would not be surprised if an agricultural biochemist was working on a GMO popcorn that would be high in RS.

    2. According to Wikipedia, popcorn has a hard starch center that gelatinizes when reaching 356 Fahrenheit. As the temperature rises higher, the kernel explodes, and the starch rapidly cools, forming the popcorn. Makes me wonder.

    3. It was a good thought! I've often wondered, too, exactly how much, but I have to assume that it is very low, like 1-2%. Not all starch is created equal.

      Regular corn starchhas nearly zero RS, a well-studied fact, due to it's high amylopectin starch content.

      Hi-Maize corn starch is specially bred to be low in amylopectin starch and high in amylose starch, a hallmark of RS.

      My guess, then, is that popcorn simply has the wrong type of starch. But until it's tested in a lab, we'll never know. There is not a single reference in a science journal to be found (Challenge! Everyone.)

    4. According to this closeup with an electron microscope(?) popcorn is made up of amylose.

      Which makes sense since popcorn has a low glycemic index, a hallmark of amylose makeup.

    5. Love it!

      I'm not sure the paper in the link says "made up of amylose," though. I think the author of the blog post was just using the term "amylose" to mean "starch". The actual label for the figure where the SEM picture came from is:

      "FIGURE 2. Scanning electron micrograph of (a) pericarp ' hull' blown free as a result of popping; (b) the outer portion of the endosperm after popping, showing the aleurone (A); (c) the inner portion of the endosperm after popping, showing the protein bodies (P) still intact; and (d) the endosperm in a partly popped kernel, showing starch granules ranging from intact to expanded forms."

      But, no matter. Let's explore!

      I can't find any papers that mention the ratio of amylose to amylopectin in popcorn, or mention of RS. Plenty of sources say that 3 cups of popped corn have 2-4g of fiber (1 soluble/3insoluble). But, RS is never accurately counted, so that doesn't mean much.

      If popcorn was a good source of RS, what would be the result of eating a "Large" popcorn at the movies? This would be the equivalent of eating potato starch by the handful. Massive popcorn consumption, if it were high is RS, should lead to massive gas.

      Maybe there's a reason they serve popcorn and not beans at the theater (JuJu beans don't count!).

      I have to stand by my initial assumption. Popcorn is a good source of fiber, but not RS. Would LOVE to be proven wrong, though!

      But, putting thinking cap on, it would be all RS3. RS3 is never found in very high amounts, especially from foods low in RS2 to begin with.

      I'll keep looking!

    6. Well for the record, my brother and I do joke about popcorn farts after the movies lol. No, I don't have access to the article, just the author claiming it was amylose based on this SEM pic:

      I tried to find a a SEM picture of amylopectin to compare, but couldn't really make heads or tails of what I found.

  10. Interesting stuff, Tim. Thanks for sharing it.

    Tim wrote: "Organic Corn Flour and Organic Quinoa Flour"

    Those are both C4 plants. Do you think it could add benefit to include C4 starch in the diet rather than just C3 starch? It seems possible, given that Homo sapiens and other hominids ate C4 plants on African savannahs. Duck wrote about it. There's an interesting CO2-enrichment aspect to C4 plants that might interest Peatarians.