Previous posts on the topic:
- Prepare for the “Resistant Starch” Assimilation; Resistance is Futile
- Resistant Starch: 4-Letter Word? Nope. Goal: Create Mashed Potatoes A Diabetic Can Eat Every Day
The interest over those posts has been rather enthusiastic, in spite of my concern over: "Oh, what new miracle is Richard-The-Traffic-Whore on about now?" And it's a legitimate criticism in my book, especially if not completely familiar with the history around here.
As I wrapped up that post yesterday:
My next post will be about the tons and tons of research into Resistant Starch in the last 30 years that's not financed by someone with a financial interest. I've collected a veritable shitload, thanks to the help of commenter, retired Air Force, Arctic Circle living, lay digger upper of research papers: "tatertot." Following that will be a post cataloging my own results over the last couple of months, as well as that of many others including my T2D mom.
Both tatertot & I firmly agree that resistant starch is an enormous blind spot in Paleo. Go look at what they find in human shit fossils (coprolites). Hint: not a full rack of ribs and a side of salad dressed in olive oil and balsamic.
Oh, "tatertot," is also just Tim. In addition to the other things I cited, he's a hunter, trapper, fisherman, weekend farmer and full-time electrical systems supervisor in a local hospital up there a short hop from the North Pole. He does not work for a starch company. Tim and I've been collaborating for months on this, but he's the one who dug up the research and connected dots. I got people interested and collected a shitload of human guinea pigs so that everyone can see soon enough if we've just been taking the piss.
Before I begin, here's a pretty good primer on the importance of gut bacteria in Mother Jones: Are Happy Gut Bacteria Key to Weight Loss? That briefly mentions resistant starch near the end—still a blind spot, in my view, but a great primer. Then there's this, from Primalmeded: Resistant starch: the missing ingredient? This strikes as a bit cherry picking in reverse, to me, on grounds that the research cited is mostly, or all, from a producer of "Hi-Maze," an engineered corn starch product. A far more balanced piece is by Norm Robillard, PhD microbiologist and former researcher, of Digestive Health Institute: Resistant Starch – Friend or Foe? (Interesting how all three citations are questions, eh?) Anyway, Norm's chief concern appears to me to be the potential for RS to aggravate Small Intestine Bacterial Overgrowth (SIBO), but in his learned defense, I suspect that's not an indictment of RS per se, but more of having vast numbers of people who've "sawed of the branch they were standing on" by a lifetime of consuming the SAD—which I'm confident he would agree contributes to SIBO. In my next post on the various anecdotes of self-experimentation I've collected, I'll speculate as to why I think it might not be too much of a concern for many.
So here we go. The science, and only the science. Here are the parameters Tim and I have been collaborating under:
- What is the optimal dose?
- What is the optimal source?
- Will it make a difference in the grand scheme of things if implemented on a world-wide basis?
- Is it contra-indicated for anybody?
- RS supports a healthy gut microbe population
- RS exhibits undeniable effect on glucose control and satiety
- RS in amounts of 20-50g /day are well tolerated
- RS can come from many sources including real food
The Claims Waiting to Be Generally Proven (hence the need for self-experimentation)
- RS prevents colon cancer, diabetes, IBS, Crohn's, and Ulcerative Colitis
- RS improves absorption of vitamins and minerals
- RS lowers levels of inflammation in gut
- RS prevents damage done by eating red meat
These are all claims made, some proven in animals. Some have been shown effective in humans, but no long-term studies.
Then there's always the underlying theme: Is it really needed on a paleo diet?
The Research. Skim, Review, or Dig In. As per your own standards.
First, here's why it's easy to get fooled of jaded by the thing. National Starch came up with a business plan to bombard the world with resistant starch in the form of Hi-Maize corn starch. Here's a press release from 2004: National Starch Expands Manufacturing to Boost Production of Hi-Maize(TM) Resistant Starch.
BRIDGEWATER, N.J., June 16 /PRNewswire/ -- National Starch announced that it completed an expansion on June 1 which increased the production capacity for Hi-maize(TM) resistant starch by 33 percent. This is the second expansion this year and provides National with ample capacity to meet increasing customer demand.
Hi-maize is the only natural, granular resistant starch available in the U.S. Within the last year Hi-maize has been formulated into many low-carb foods because of its ease of use, its natural identity and its strong clinical support. ...
In fact, National Starch would love to have you shove Hi-Maize straight up your ass! So, yes, indeed, there is a profit motive here, and engineered unnatural (expensive) product "app for that;" and they would never, ever tell you there's a cheap alternative in the form of Bob's Red Mill Potato Starch that mixes great with all sorts of things and costs pennies per day (and is 80% RS by weight).
NOW the Real Research, and Only the Research
Fortunately, there are lots of papers, studies, abstracts, etc... talking about the the legitimacy of using natural RS for digestive health. Perhaps it's from these studies that National Starch got its ideas. Here's only a partial list of the research, none paid for or affiliated with National Starch.
~ Resistant starch: the effect on postprandial glycemia, hormonal response, and satiety (human study—abstract). "In conclusion, the replacement of digestible starch with RS resulted in significant reductions in postprandial glycemia and insulinemia, and in the subjective sensations of satiety."
~ Digestion and physiological properties of resistant starch in the human large bowel (human study—abstract). "We have concluded that RS2 and RS3 are broken down in the human gut, probably in the colon although in 26% of cases this breakdown was impaired. RS exerts mild laxative properties, predominantly through stimulation of biomass excretion but also through some sparing of NSP breakdown."
~ Fermentation of dietary starch in humans (human study—abstract). "CONCLUSION: A high-resistant starch diet and its resultant increase in fermentation products may be partly responsible for protecting the black population against colorectal cancers and other large bowel diseases."
~ Intakes of Carbohydrates and Resistant Starch Food Sources Among Regular Exercisers in Blacksburg, VA and San Jose, Costa Rica (human study—full text). "Consumption of RS prior to prolonged exercise could cause stable glycemic and insulinemic responses that may help delay the onset of fatigue during exercise."
~ Starch and Fiber Fractions in Selected Food and Feed Ingredients Affect Their Small Intestinal Digestibility and Fermentability and Their Large Bowel Fermentability In Vitro in a Canine Model (dog study—full text). "Potato flour resulted in the highest (P < 0.05) total SCFA production compared with all other flours...also found that potato flour was numerically highest in total SCFA production when comparing six different flours incubated in inoculum containing ileal microorganisms."
~ Sources and intake of resistant starch in the Chinese diet (human study—full text; tons of charts). "The resistant starch contents of 121 foods were determined using a method that mimicked gastrointestinal conditions. Tubers and legumes had high resistant starch contents. Rough food processing retained large amounts of resistant starch. In general, the content of RS decreased when foods were cooked. Deep fried and roasted foods had higher levels of resistant starch than braised foods. The average resistant starch intake in the Chinese population was estimated to be 14.9 g per day based on a dietary survey. The main resistant starch sources in the Chinese diet were cereal and tuber products. Based on dietary habits, however, the resistant starch intake varies considerably among individuals."
~ The Second-Meal Effect: A Review (human review study—full text). "Consumption of low glycemic-index (LGI) foods has been shown to attenuate blood glucose response during the postprandial period immediately following a meal. In addition, positive metabolic effects can persist well beyond this period. One of these extended effects, known as the “second-meal effect,” is the positive effect of the bioavailability of glucose on the glucose tolerance of the subsequent meal. This secondmeal effect, initially observed in normal-weight, healthy adult subjects using glucose and guar, has also been documented in patients with type 2 diabetes. ...However, a growing body of animal data suggests that the effect may also be mediated by SCFA produced from colonic fermentation whereby SCFA attenuate postprandial blood glucose levels of the subsequent meal by inactivating hormone-sensitive lipase in
adipose tissue via the intestinal incretin GLP-1 or via the G-protein receptor GPR43."
~ An In Vitro Method, Based on Chewing, To Predict Resistant Starch Content in Foods Allows Parallel Determination of Potentially Available Starch and Dietary Fiber (full text). "It is concluded that the procedure described here provides a convenient way to estimate RS content of realistic foods, allowing parallel determination of the potentially available starch fraction and dietary fiber."
~ Effect of the glycemic index and content of indigestible carbohydrates of cereal-based breakfast meals on glucose tolerance at lunch in healthy subjects (human study—full text). "Conclusions: Glucose tolerance can improve in a single day. Slow absorption and digestion of starch from the breakfast meal, but not the content of indigestible carbohydrates in the breakfast meal, improved glucose tolerance at the second meal (lunch)." Potato starch used in this intervention, and found to be superior.
~ Resistant Starches Types 2 and 4 Have Differential Effects on the Composition of the Fecal Microbiota in Human Subjects (human study—full). "Our results demonstrate that RS2 and RS4 show functional differences in their effect on human fecal microbiota composition, indicating that the chemical structure of RS determines its accessibility by groups of colonic bacteria. The findings imply that specific bacterial populations could be selectively targeted by well designed functional carbohydrates, but the inter-subject variations in the response to RS indicates that such strategies might benefit from more personalized approaches."
~ Starch (90-page Scientific Presentation; note from North Pole Tim: "The most informative paper on starch and RS in general. A 'must read' for everyone talking about RS.")
~ Fermentation of Native Wheat, Potato, and Pea Starches, and their Preparations by Bifidobacterium – Changes in Resistant Starch Content (human study—full text). "Bifidobacterium strains selected for this study: B. pseudolongum KSI9, B. animalis KS20a1, and B. breve KN14 used the native starches from three origins and their preparations as a source of carbon and energy for their growth. Generally, the resistant starch fractions from native starches were better substrates and their utilisation was higher compared to the modified starch preparations. A significant decrease in the level of resistant starch was observed in native potato and pea starches and their preparations after 24-h fermentation with the Bifidobacterium strains examined in the experiment. However, the gelatinisation process of native starches and their preparations had negligible influence on the resistant starch metabolism by the selected bifidobacteria."
~ Assessing prebiotic effects of resistant starch on modulating gut microbiota with an in vivo animal model and an in vitro semi-continuous fermentation mode (animal study—197 pg. doctoral dissertation). "In summary, our studies with both in vivo animal model and in vitro fermentation model supported previous recognition of resistant starch acting as a prebiotic to modulate gut microbiota, especially on Clostridium clusters IV and XIVa. Ruminococcus bromii was specifically induced in rat model fed RS as well as in vitro fermentation model using lean microbiota. Moreover, different RS may have different fermentation outcomes. Our findings provided solid evidence to answer the fundamental question of how RS exerted effects on ix shifting bacterial pattern. In addition, we also showed that the physiological significance of RS might be affected by physical-chemical properties of starch and pre-existing microbiota as well. [...]
"Beyond RS, there are many other questions remaining to be answered, such as how many bacteria species or strains are required and sufficient to attain beneficial effects? Will it be possible to targeting specific bacteria species to introduce or deplete it in humans? Whether bacterial pattern can be sustained after dietary intervention stops? Are there other metabolites of gut microbiota playing a crucial but undiscovered role to improve human health? Other more practical concerns are what food products and appropriate dose is needed to be included in the diet without comprising individual food preference and habits but obtain equivalent beneficial effects?"
Tatertot Tim comments: "Clearly, to me, the answer to all of these question lies in the use of resistant starch to achieve the level of manipulation needed. I think for the average Joe, just getting some RS in your diet, whether from food--which is hard, or supplementing with potato starch--cheap and easy--is the best you can do to give your guts the best chance they have at creating what they need to thrive.
"Also, this study shows me that RS is clearly not 'just fiber' as so many people love to say. If it were 'just fiber' would so many studies be performed, so many thesis papers written, and so much time and money be devoted to study it?"
I actually have substantially many more. I had about 6 more entries done, such as are above, drafted & formatted below. They're part of a Part 2 draft, now, but I just had to cut this shorter for now, always wishing to strike the balance about things.
So this ought be where RS related discussion in comments moves, from back there at 438 90%-awesome-comments-so-far...flamewar free. Yea! A 438-comment thread at Free the Animal without any flamage.
...How boring, eh!?
Keep this in mind. The idea for my fundamental motivation behind all of this is simple: if 10% of us ought to eat right, then it might be good to understand what the other 90% of us ought to eat. Get it?
I'll be back very soon, even if you see something else pop at at the top in the interim.