Low GI Mashed Potatoes! and the Resistant Starch Content of Foods

Yesterday we saw that beans are low GI and why (resistant starch), and how they even have a "second meal effect" into the following day where BG spikes are significantly blunted in subsequent, non-bean, high GI meals. Potatoes are high GI, typically causing significant spikes in blood glucose—not the best choice for diabetics. But is there a way to prepare, say, mashed potatoes in a way that would not only make them significantly lower GI, but creating a second meal effect as well?

OK, so per Tatertot Tim, here's a list of the resistant starch content of various foods (he hasn't thoroughly verified some of these but believes it to be largely accurate).

  • Raw Potato Starch: 8g/TBS
  • Raw Potato: 25g per 100g
  • Cooked Potato: 2-5g per 100g
  • Cooked and cooled potato: 5-10g per 100g
  • Legumes/Beans/Lentils: 5-10g per cup, cooked
  • Corn Tortillas - 1-2g per
  • Cooked Rice - 2-9g per 100g
  • Cooled Rice- 5-13g per 100g
  • Buckwheat Flour - 4g per TBS
  • Plantain Flour - 5g per TBS
  • Dried Plantains - 50g per 100g
  • Green Banana - 10-20g (small-large)
  • Ripe Banana - 0g
  • Hi-Maize Corn Starch - 5g per TBS
  • Regular Corn Starch - 1g per TBS (or less)
  • Beets - 0g
  • Turnips - 0g
  • Carrots - 0g
  • Jerusalem Artichokes - 0g
  • Wheat Flour - 0g
  • Uncooked Wheat - 2g per 100g
  • Uncooked Oats - 20g per 100g

The Resistant Starch content of food changes. It's different when raw compared to cooked, and different when cooked in various ways, and different when cooked and cooled. There's no official way to measure RS. The gold standard is the 'ileostomy method' also called 'in vivo'. They feed a person or animal a food, then examine the contents of the small intestine just before it dumps into the large intestine—any starch found is RS. The second method 'in vitro' or test tube method, treats food with acids that act like digestion and then they measure remaining starch. Both methods get similar results.

...So way back when, I had the idea to make "mashed potatoes" but to preserve all the RS, which would be a huge amount; e.g., a 1 pound raw tater contains over 100g RS. My efforts were not successful, even doing them sous vide for 24 hours. I can't find it in my folder but Tim had a different idea, which was to cube and cook them in water at less than 140F, then drain and season. He liked them and sent along his BG readings which didn't budge, lending evidence to the idea that the RS content completely blunts the glucose spike—to absolutely ZERO in this case.

A couple of weeks ago we came up with exactly the same idea concurrently, same day. Here's the idea:

  1. Make mashed potatoes as you normally make them.
  2. Once drained and ready to mash or purée, do it first with just the butter and then let sit for a few minutes to cool, slightly.
  3. Make a cold milk or cold cream slurry with your Bob's Red Mill Potato Starch. I just randomly decided I'd start with One TBS per medium to large potato, 1/4 - 1/3 cup of milk or cream per, as well. It may turn out that more is needed, or it's enough, or more than needed.
  4. Introduce the slurry, mash or purée. I highly doubt that the potatoes in combination with the cold liquid are going to be hot enough for long enough to burst the starch granules.
  5. Eat, measure your BG over time, and compare it to the same conditions with mashed potatoes without the RS. To avoid confounders, I'd just eat them plain with some seasoning.

I did mashed potatoes like this just last night, but I didn't measure anything because I had confounders all over the place:

Salisbury Steak and Resistant Starch Mashed Potatoes

Here's the post from the first time I did salisbury steak. It's adapted from this recipe. No breadcrumbs, and rather than the roux, I simply thickened with...you guessed it...potato starch in a slurry of cold beef stock.

Out of the oven, 375F for 35 minutes

All I know is that usually, when I do eat a big plate of mash I usually end up a bit comatose after a couple of hours. Nothing of the sort, and also: zero fartage.

Alright, that should give some of you N=1ers something to do. So go do it and report back. Please make sure to report how much potato starch you decided to use per potato. Ideal would be to report the weight of the potato as well.


  1. James Warden says:

    Great stuff man! A few hours ago, I had ordered 2kg of potatoes for my weekly food delivery. I did not know exactly how I would cook them but now I know :D :D

    By the way, it would be interesting to measure the insulin response, not only the blood glucose levels because dairy proteins (ingested alone) are known to trigger some good insulin response but at the same time an increase of glucagon to PRESERVE a normal BG level. If that was not the case, you can imagine that digesting dairy proteins would leave us hypoglycemic … Mashed potatoes (MP) are a mixture of dairy and starch: so I would suspect a huge insulin spike with regular MP and no glucagon release. This would explain your former post-MP coma …

    • In that case, James, in order to minimize confounders, I’d use cream instead of milk.

    • OTOH, this was probably 5-6 oz of whole milk for two enormous potatoes and between Beatrice & I, there was quite a lot left over, as well as steak. In fact, just had leftovers for breakfast. What I did was microwave just the burger and sauce, and then pour it all over cold mashed taters I’d spread out on the plate so as to warm them, but not kill the RS.

  2. I thought about bringing a ziplock bag of potato starch with me on a flight to San Fran. But I decided not to. No officer, it really is potato starch…

    • Mhustonwa says:

      Hilarious. Just did same avoid-white-powder+TSA routine for my flight to Philly. Thought it esp. wise since one of our workshop particpants last week *was* detained for, drum roll, baby powder in her carryon…

  3. Richard, since you’ve been taking RS ~daily for a while, do you think it’s possible that there’s a persistent ‘second meal’ effect from the ~daily RS? If you have had mashed potatoes since starting RS and still been ‘comatose’, then that possibility goes away. Do you remember when was the last time you had them?
    if not, gee, for the sake of science, can I get you to eat again this delicious meal without the RS? Sacrifices, I know…. ;)

    Tatertot and I have been working on that. There are more variables we’re looking at, report next week when a controls will be done.

  4. Tatertot says:

    I have about 10 studies with tables for over 200 different food items. I’m putting them together in one place with references and testing method used. I hope everybody prints the list above and puts it on their fridge!

  5. Deidre says:

    I am an “almost” Type 1 diabetic (LADA…latent autoimmune diabetes in adults). Just diagnosed so still in the honeymoon period before insulin but zero blood sugar control. I just had 2 slices of gluten free pizza (also Celiac) with a GF beer (Omission Ale…v.good). Guaranteed to send my blood sugar readings thru the roof. I decided to gulp down 1 TBS potato starch in a glass of water before eating. And 1 hour later my reading was 110. Checked it again…111. Very pleased. I have been testing a nightly dose for 2 weeks and it definitely has improved my sleep/dreams. Very exciting stuff. Thanks so much for putting this information out there.

    • Tatertot says:

      That is awesome. The trouble with most RS and fiber, is it comes along with a bunch of carbs and calories, so trying to increase fiber/RS usually results in an increase in calories/carbs. That is not a problem for me, but I can see it as a big problem for many. Using potato starch as a substitute for real-food RS could be a game-changer for lots of people. RS with no carb-load or glycemic impact. You can’t say that about potatoes, beans and rice.

  6. Out of curiosity, would instant mashed potatoes be the same thing?

    • Tatertot says:

      If you mean, ‘could you make instant mashed potatoes, let them cool a bit and then stir in some potato starch to lower their GI?’, then , yes.

      If you mean, ‘are instant mashed potatoes a good source of RS?’, then , no.

      Even if you ate instant mashed potatoes dry, right out of the box, nearly all the RS has been cooked out of them in their processing.

      • Thank you.

        I was wondering if instant mashed would contain RS.

        Your answer is appreciated.

  7. So I just received my order from Amazon (my local market carries every Bob’s Red Mill product EXCEPT potato starch). What are the most common ways of ingesting it? I can see it getting used somewhat in cooking but last night I just dumped 4 TBS into a glass of water like it was protein powder.

    • Tatertot says:

      Don’t use it in cooking–the RS is lost when heated!

      Mix it in water, milk, ice cream, yogurt, sour cream, kefir, etc…

      I usually have a potato every day, I mix 1-2TBS of potato starch in some sour cream and mix it in with the potato once it has cooled a bit–warm is OK, steaming hot not OK. But just mixing it with water is really simple and painless–I do that on occasion, too.

  8. Bernardo says:

    Hey! Bought myself some potatos to try the RS approach for a while. The way I’m doing it is:

    1- Fry some garlic and/or onion in some coconut oil (or butter)
    2- Dice the potatos, but not too much (I got myself small-sized red skinned ones – so just 1 cut),
    3- Throw the potatos and salt in the pan with the frying garlic/onion just enough to warm and coat them
    4- Throw some shredded cheese and bacon chips on top :P

    Do you think this method is safe enough to preserve the RS in the potatos? It was really good and I’d guess the chunks were quite raw inside.


    • Tatertot says:

      I think that is a really good method. You can probably dice the potatoes as small as you like as long as you don’t end up cooking them through. Frying a couple pieces of bacon in the pan would probably be good, too!

      Actually, it sounds so good I will probably try it tonight! Thanks

  9. Any ideas on some of the less common starches like arrowroot, kudzu (or kuzu) or tapioca??? I have a GI disease and have used the first two in particular, with great success to sooth the stomach and during flares. Kudzu tea is known as a popular Macrobiotic ‘remedy.’ Maybe the help because of RS???

    • Tatertot says:

      Ahhh! Just found this and haven’t read it…have a look and see if it addresses your concerns. I can’t open it for some reason (outdated browser probably). I can’t imagine kudzu tea would have any RS, I’m imagining a tea made from those weeds that grow all over powerlines and old barns in the Alabama, maybe I’m way off target! Arrowroot has very little if I recall correctly and tapioca starch is about 50% by weight. Must be consumed in raw state!

      “Assessment of underutilized starchy roots and tubers for their applications in the food industry”


      • I was wondering if drinking the RS right before the meal or maybe waiting ten to fifteen minutes would accomplish the same results? I find it less complicated to just slam it with some water before the meal than worrying about mixing it with my food and hope the RS doesn’t burst. So I guess I’m just wondering if there is something better about mixing it with the meal that I don’t know about?

  10. Good recipe!!!

  11. Hi, I’ve been trying to increase resistant starch in my diet lately, but I’ve started worrying about something.
    It’s very likely that my health problems are caused by SIBO, although I’m not entirely sure. Do you know if adding more prebiotics (PS, onion, garlic, chicory, artichoke, leeks, etc.) could worsen SIBO? Is it possible that prebiotics feed the pathogenic bacteria in the small intestine?

    Thanks for all the information, and thanks in advance for your reply

  12. Dr. Curmudgeon Gee says:

    @tatertot (or any resident RS experts)

    raw -> RS
    cooked -> (almost) no RS
    cooked then cool -> RS


    but if you heat it up again, i.e.,

    cooked then cool then heated it up -> still RS??? or RS disappear?

  13. La Frite says:

    As far as I understand it, RS3 (retrograded RS) keeps better when reheated. You can cool down and cook again a couple of times to increase RS3. bets is to cook with warm fat apparently.

  14. Tatertot says:

    Hey, guys – From what I am reading, RS3, the kind of RS that is formed from cooked and cooled starch, ends up with the starch no longer in granule form (like RS2) but with the starch held together by a crystalline structure, making it resistant to digestion none-the-less.

    Some studies suggest that RS2 and RS3 benefit different beneficial gut microbe populations, so it’s probably important to try to get both types on a regular basis. Raw potato starch is pure RS2. So, if you eat most of your starchy foods in a cooked–cooled–reheated (or cold) fashion, you will take care of the RS3 portion. How big a deal this is nobody knows, but I like the thought of it. It kind of takes care of the nagging fact that much of our evolution occured after we mastered fire.

    RS1, ‘RS that is physically inaccessible because of a seed coating’ is still a bit of a mystery to me. If I coat potato starch in cement and eat it, is it RS1? Does RS1 just pass through and benefit nothing? Flax seeds contain RS1, but if you grind the flax seeds to make the insides bio-available, is it still RS1? Don’t know–not much written on this.

    So, back to the question posed by the good doctor:

    You have it right.

    - Raw potato, green banana, dried plantains = lots of RS2, no RS3.
    - Cooked potato, rice, beans, plantains = little bit of RS2, no RS3.
    - Cooked and cooled P,R,B,P = lots of RS3, a little RS2.
    - Cooked, cooled, reheated via a wet method (boiled, steamed) = Little RS2 or RS3
    - Cooked, cooled, reheated via a dry method (open baked/roasted, fried) = a little RS2, lots of RS3.

    One area I’m not 100% clear on, is if there is MORE RS3 in the cooked, cooled and re-heated via dry method than in cooked and cooled. It looks like there is according to charts in studies that study this, and it may well be true. It has to do with removing water and creating more RS.

    I found a paper on how to increase RS in tapioca starch and it involved repeated cooking and cooling cycles, that’s also how they make SuperStarch, so at some point, the RS must be increasing after being heated.

    If you want to explode your brain, do a google search for terms like starch hydrolysis, pasting properties of starch, starch viscosity, and retrograded resistant starch. This is a science all it’s own.

  15. Can I assume those weights for rice are for cooked rice?

  16. tatertot says:

    @Mark – all weights are given ‘as eaten’ unless otherwise noted.

  17. Julian Carter says:

    Would anyone know if wild rice, which is a grass, is acceptable on a paleo eating plan? Thanks.

  18. Guilherme says:

    Apparently, you can heat tapioca flour to make ‘tapioca tortillas’ (common thing here in Brazil, we call it just “tapioca”) and it will still have a good amount of RS.

    From http://www.ppgcta.ufc.br/cristianealexandrino.pdf
    “The tapioca with cassava showed the biggest degree of gelatinization (61.63%) and resistant starch (42.23%)”

    The tapioca made with potato starch had about 25% RS, but after 48 hours it went up to ~60%.
    To make tapioca paste, just mix the starch with water, coconut flour and salt. Then heat it like pancakes and wrap stuff with it. I’ll be eating more of those now =)

  19. Very excited to know about tapioca’s high RS content. I am Brazilian and very familiar with them. I will be eating more often and guilt free. Thanks :)

  20. I wonder if the crystalline structure grows similar to the gigantic underground gypsum crystals found in deep caverns. It seems that hot saturated gypsum water creates incredibly large crystals over long periods of time. If crystals increase in size when in the presence of a saturated solution of whatever the crystal is made out of, with starch it may be the same process at work. I guess that begs the question: If you cook a food at below gelatinization temperature for a long period of time then cool, would the retrograded RS3 starch crystals be larger and / or in more abundance?

  21. Tee Dee says:

    I remember years ago my Aunt was supposed to do the potato salad for a family bbq we were attending that Sunday. She showed up somewhat embarrassed because she’d forgotten to buy potatoes and make it the day before, so she used instant mashed instead. Everyone still loved it and some of us even started to use our leftover mashed potatoes to make potato salad. Everything else in the recipe is the same: mayo, green onions, hard-boiled eggs, chopped pickles, etc. (or whatever you normally put into your tater salad). Just an idea for the summer bbq season and no worries about how much to heat it and ruining the RS you’ve added, since you want your salad cold anyway :)

  22. Susie Goldfish says:

    Does the microwave count as “reheated via a wet method”?

  23. I’m surprised no one’s talked about juicing raw potatoes. i just started doing it, adding in a little carrot, cucumber, or whatever to make it palatable. 100 mg. of raw potato is actually a very small size. i’m also going to buy the starch, because i don’t see myself juicing every day. i do like the idea of eating foods in their natural states as much as possible though. i suspect there’s a lot of nutrition in a raw potato that might not be there in the powdered starch form. by the way, if you try juicing, make sure you don’t just slug it down and throw the glass in the dish washer. the starch seems to concentrate at the bottom of the glass in a dense layer, so be careful you don’t toss out the important part.

    • Robin:

      Well, seems you are at least getting some of the starch out of the potato, but since juicing is by definition to be rid of the fiber, some of those tiny granules are going to end up staying with the other fiber. The other reason is that if someone is going to have intolerance to potato, it’s definitely going to be exacerbated by taking it raw. Solanine, for instance, is water soluble so the process of rinsing raw potatoes with water to get the starch out gets rid of most of that.

    • I see what you mean, but I have a feeling a lot of the starch goes into the juice when you use a good juicer (not the centrifugal type). The starch is water washable, and doesn’t have any specific reason to cling to the fibers. The pulp that came out was very dry and didn’t feel starchy when I rubbed it between my fingers (whereas the juice felt and tasted very starchy). There’s no way to know exactly how much I’m getting out, but I’m guessing at least 80%. In any case, i’m not concerned about knowing down to the milligram how much I’m taking in. A rough idea is good enough for me!

    • C Kelsey says:

      Robin…put your “waste” from juicing the potato into a bowl of water and squeeze it with your hands…you will get an idea of how much starch remains in the fiber by how cloudy the water gets.

  24. RE: Dreamfield pasta effect? No blood sugar impact at 1-2 hours, but it was found around 5 hours postprandial if I recall. I have not measured my blood sugar that far out, but was told the potato starch one of the most high GI products available. Do you think he is getting potato starch mixed up with potato flour? Thanks for the info.


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