What’s the Trouble With Sweet Potatoes?

We’re continuing with a series on people who have reported something going wrong when they tested some variation of the Perfect Health Diet. (The first post summarized experiences, good and bad; the second looked at difficulties suddenly adding carbohydrates to a very low-carb diet.)

The next issue was reported by Chris Masterjohn; he had trouble with sweet potatoes:

Although sweet potatoes are considered a safe starch on the Perfect Health Diet, they are not very safe for me. When I discovered how yummy sweet potato fries are, I started eating several sweet potatoes per day. Within a few days, I was limping and my neck was stiff. By the end of the week, my limp was extreme. I looked online to see if I was eating anything high in oxalates, and sure enough, sweet potatoes are loaded with them. My symptoms dramatically improved after one day off sweet potatoes and were gone the second day.

Chris’s commenter Lisa also had trouble with sweet potatoes:

I’ve been very achy since I started eating sweet potatoes daily. Why would some of us be maladapted to oxalates?… I’m wondering if after a long stint of LC/paleo eating I’ve become intolerant to oxalates or to starch in general.

Clearly sweet potatoes are not safe for everyone. What might be causing the trouble?

Fructose and Fiber as Possible Confounders

One factor to consider is that there are different varieties of sweet potato. We eat an Asian sweet potato variety which is not nearly as sweet as conventional American sweet potatoes; it has a yellow flesh and a chestnut flavor. It is botanically a yam, not a sweet potato. It looks like this (via “my super sweet twenty-six”):

Like so many modern foods, the standard American sweet potato has been bred for sweetness. Here is data from http://nutritiondata.com comparing 100 g of potatoes, yams, sweet potatoes, and grapes for sugar, starch, and fiber content:

Food Sugar (g) Starch (g) Fiber (g)
Potato 1.2 17.3 2.2
Yam 0.5 23.1 3.9
Sweet potato 6.5 7.5 3.3
Grapes 15.5 0.0 0.9

All have similar calories. Yams are largely sugar-free, but sweet potatoes are intermediate between grapes and potatoes in both sugar and starch content. They are sort of half fruit, half starch.

Thus, it is conceivable that sweet potatoes could trigger an issue like fructose malabsorption; or that fructose or fiber might feed certain gut infections that would not be similarly fed by potatoes.


Chris believed his problem was due to oxalate. Sweet potatoes do contain oxalate, although they are not the only plant foods which do.

In fact, by far the largest source of oxalate in the American diet is spinach. Spinach by itself accounts for over 40% of all oxalate consumed by Americans; potatoes for about 10%. [1] Wheat bran has high levels of oxalate.

Why are oxalates troublesome?  Some people have sensitivities to oxalate. Rarely, genetic defects in the enzymes that degrade oxalate cause a disease called primary hyperoxaluria; this disease afflicts 1 to 3 people in a million.  Other conditions can elevate calcium or oxalate in the urine and increase the risk of calcium oxalate kidney stones. This is especially likely in people who are deficient in magnesium or who don’t eat citrate. [2]

Another pathway by which oxalate might cause trouble is via fungal infections. Candida and other fungi form calcium oxalate crystals in tissue [3,4]; fungi appear to be responsible for the yellow-brown calcium oxalate biofilms which form on stone monuments. [5]

But the literature suggests that oxalate sensitivities are rare. If oxalate sensitivity is present, then it should manifest itself when eating spinach, wheat bran, and other oxalate rich foods. Since Chris has praised spinach and wheat recently, I wonder if it is really the oxalate that caused his trouble.


Another possibility is a class of toxins called phytoalexins.

Ordinarily, sweet potatoes are largely toxin free. But when attacked by fungus or molds, sweet potatoes generate a variety of food toxins. As two papers describe them:

Sweet potatoes contain phytoalexins that can cause lung edema and are hepatotoxic to mice. At least one of these, 4-ipomeanol, can cause extensive lung clara cell necrosis and can increase the severity of pneumonia in mice. Some phytoalexins in sweet potatoes are hepatotoxic and nephrotoxic to mice. [6]

Ipomeanine (IPN), 4-ipomeanol (4-IPO), 1-ipomeanol (1-IPO), and 1,4-ipomeadiol (DIOL) are toxic 3-substituted furans found in mold-damaged sweet potatoes. IPN and 4-IPO are the most toxic, but all produce pulmonary toxicity in cattle and rodents, and 4-IPO induces hepatotoxicity in humans. [7]

Cattle will die if fed mold-damaged sweetpotatoes:

Unfortunate bovine fatalities occurring after ingestion of mold-damaged sweetpotatoes preclude the use of the culled tubers in livestock feed. In cattle, mold-damaged sweetpotatoes induce an acute respiratory distress syndrome resulting in asphyxiation. [8]

Toxins may be present even if mold damage is not visible:

Fermentation of 6 weeks duration was observed to inadequately eliminate the lung, liver, and kidney toxicity caused by mold-damaged sweetpotatoes. In fact, fermentation exacerbated the hepatotoxicity of mold-damaged sweetpotatoes. This is also the first demonstration that sweetpotato regions lacking visible mold damage can induce lung and kidney injury … [8]


Sweet potatoes are generally considered to be one of the least allergenic of foods. However, infants sometimes do have sensitivities to sweet potato. This may reflect an immature gut flora in the infants; perhaps specific bacterial species — possibly including the oxalate-digesting Oxalobacter [9] — make sweet potatoes tolerable? If so, it raises the possibility that adults with incomplete gut flora might also have sweet potato sensitivities.

There is also the possibility of allergies to mold toxins in infected sweet potatoes.

Food Sensitivities as a Diagnostic Tool

Food sensitivities can sometimes be helpful in diagnosing certain health conditions:

  • Leaky gut. People with a leaky gut will have many food sensitivities; people with a healthy gut will have few.
  • Small bowel infections. People with infections of the small intestine will usually have a negative reaction to fructose.
  • Colonic infections. People with infections of the colon may react badly to fiber, and obtain relief on low-fiber diets.

There is a chance that oxalate may benefit fungal infections, so I suppose an oxalate sensitivity could be diagnostic for that, although in my experience fungal infections are usually slow-reacting to food and the response is rarely obvious.


In our book [p 121] we note that all plants make pesticidal toxins. Thus, no plant food can be guaranteed to be safe.

Normally, levels of pesticidal toxins are low in sweet potatoes. But it’s always desirable to inspect sweet potatoes for visible damage, and to discard any that are discolored or show other evidence of toxin production.

I confess to being puzzled as to how sweet potatoes caused Chris’s symptoms. If he tolerates spinach and wheat bran, it seems unlikely that the oxalate in sweet potatoes would be responsible. He might wish to test various foods and try to narrow down the source of his sensitivity.

For our part, we may cease listing sweet potatoes among our “safe starches” and specify yams instead, since a “safe starch” should probably be low in fructose.


[1] Taylor EN, Curhan GC. Oxalate intake and the risk for nephrolithiasis. J Am Soc Nephrol. 2007 Jul;18(7):2198-204. http://pmid.us/17538185.

[2] McConnell N et al. Risk factors for developing renal stones in inflammatory bowel disease. BJU Int. 2002 Jun;89(9):835-41. http://pmid.us/12010224.

[3] Takeuchi H et al. Detection by light microscopy of Candida in thin sections of bladder stone. Urology. 1989 Dec;34(6):385-7. http://pmid.us/2688263.

[4] Muntz FH. Oxalate-producing pulmonary aspergillosis in an alpaca. Vet Pathol. 1999 Nov;36(6):631-2. http://pmid.us/10568451.

[5] Pinna D. Fungal physiology and the formation of calcium oxalate films on stone monuments. Aerobiologia. 1993 9(2-3):157-167. http://www.springerlink.com/content/n72l71352t1r0r04/.

[6] Beier RC. Natural pesticides and bioactive components in foods. Rev Environ Contam Toxicol. 1990;113:47-137. http://pmid.us/2404325.

[7] Chen LJ et al. Metabolism of furans in vitro: ipomeanine and 4-ipomeanol. Chem Res Toxicol. 2006 Oct;19(10):1320-9. http://pmid.us/17040101.

[8] Thibodeau MS et al. Effect of fermentation on Sweetpotato (Ipomoea batatas) toxicity in mice. J Agric Food Chem. 2004 Jan 28;52(2):380-4. http://pmid.us/14733525. B76FN5FG89GM

[9] Hatch M et al. Enteric oxalate elimination is induced and oxalate is normalized in a mouse model of Primary Hyperoxaluria following intestinal colonization with Oxalobacter. Am J Physiol Gastrointest Liver Physiol. 2010 Dec 16. [Epub ahead of print]. http://pmid.us/21163900.

Leave a comment ?


  1. I was going to ask if iodine could possible help with GERD problems. You had suggested to me before that there was a possibility that I had some fungal infection. Seems there might be some connection after all. I had been wondering if this was going to be a silly question.

    I have also been drinking a lot of milk kefir and lemon water, that might also be helping. It´s still early to tell if this is permanent or not but it´s nice to feel that there is some progress.

    I discovered quite clearly that rice made my symptoms worse. But I seem to tolerate sweet potato fine and other starchy tubers. Do you have any idea why white rice could have made it worse, since you recommend it for GERD symptoms for pure glucose?

  2. Hi Anna,

    Iodine helps a little with all problems. It is not a cure but it should make your immune system work a bit better.

    Milk kefir and lemon water are good.

    Sweet potatoes and tubers have a lot of fiber and feed colonic bacteria better, rice/glucose gets digested more in the small intestine and might feed an infection there.

    I recommend rice because it’s better than fructose and you need some glucose, and most people have more problems in the colon than the small intestine … but if tubers work better for you, then go with them.

  3. Thank you.

    So I might in the future be able to tolerate rice?

    Not that I´m a big fan of rice but it´s cheap, convenient and offers more variety so I wouldn´t mind it occasionally.

    I have been taking more iodine dose faster than you recommend. The fact that my GERD problems have improved but otherwise I don´t notice anything different I´ve been assuming it´s been ok. I´m up to 3mg in a month. I was trying to find the tolerance but I guess I will slow it down for now.

  4. Chris may have a leaky gut due to the wheat he is consuming. Every plant food has lectins. The lectins in the sweet potato may trigger an autoimmune reaction in Chris. I would say stop the wheat Chris and try the sweet potatoes again after a month or so. VBR Hans Keer

  5. Hans,

    I’m not sure I was eating any wheat at all while I had the issue with the sweet potatoes; I think I had been gluten-free for a while. In any case, I’m not sure why you think wheat would cause leaky gut in someone without celiac, given that Dr. Fasano just published a study showing that people with non-celiac gluten sensitivity have *decreased* gut permeability relative to controls and that the Australian researchers who just published a double-blind placebo-controlled trial feeding gluten to people with non-celiac gluten sensitivity for six weeks found that it did not result in any changes in intestinal permeability.



  6. Hi Paul,

    I’m new here and basically need some help posting questions as I am not sure where I go to post them?

    I will outline them quickly now, but would like to know how to do properly next time.

    Firstly just a quick question on white rice. I have always avioded white rice because I was under the impression that because it was so refined it is quick to spike insulin levels? Therefore I have always stuck to brown rice, which basically i appear to be fine with.

    Also what are thoughts on chickpeas & homus? I eat homus occasionally, though not enough to assess if i have any real problems with it, but my partner eats it all the time.

    Also I was wondering about Amaranth? Is this a safe grain?

    By the way I am really enjoying your book. I have been basically eating paleo for a little while now since finding out i was having problems digesting certain fruits etc (use to be a massive fruit & honey eater, and basically carbs in general), but your book is laying it out a little clearer and easier to follow for me.

    Thanks heaps,

  7. Also I just remembered another Question related to the white rice.

    What about rice milk?
    I was drinking a fair bit for a while as a substitute to dairy, because even though I do prefer to drink Raw goats or cows milk, too much can irritate me.
    But like with the white rice, even though I didn’t notice any adverse effects I also decided to majorly limit it due to it’s high glycemic nature.

    Thanks again,

  8. High Danny,

    There’s nothing wrong with a little insulin. A bit of temporary food-related insulin may even be beneficial and, by increasing insulin sensitivity, will likely actually lower fasting insulin.

    On a low-carb diet, you shouldn’t worry about glycemic index.

    Brown rice is OK, but white rice is better because of low toxin levels.

    Rice milk – the rice part is fine, but check the ingredients to see if they have safflower oil or other high omega-6 oils, or some other ingredients we would be wary of.

    Chickpeas – they’re a legume and I avoid them on principle. There is a paper reviewing chickpea toxicity and how it may be reduced (http://www.ncbi.nlm.nih.gov/pubmed/2467276) but I haven’t read it yet. I guess I’ll have to read it and do a blog post on it. They may be detoxified by cooking, sprouting, or soaking. You might google Stephan’s site to see if he’s discussed this.

    Amaranth – it’s probably similar in profile to quinoa, discussed here: http://perfecthealthdiet.com/?p=582. There are papers on it (http://www.ncbi.nlm.nih.gov/pubmed/10798343, http://www.ncbi.nlm.nih.gov/pubmed/17511467, http://www.ncbi.nlm.nih.gov/pubmed/1830753) but again I haven’t read them. Amaranth grains do have a high protein content (15%) which is often a warning sign.

    At first glance, amaranth appears moderately safe; chickpeas are toxic raw but may be adequately detoxified by overnight soaking and thorough cooking. I would eat them in moderation if you choose to do so.

    Best, Paul

  9. Thanks heaps Paul, that helps alot.

    Though just one other thing with it also.
    What is your thoughts on consuming these safe carbs/starches before a workout?

    I have been trying out eating mainly fats and maybe a little bit of protien before workouts to try and get my body to become more effecient at utilising fats for fuel. But generally so far I get very flat and struggle through the workout when I do this, I was even starting to find myself getting a little dizzy later on after the workouts.

    I definitly find I feel much more energetic during a workout if I add some carbs with the fat and protien etc, but I’m worried that I will continue on to forever being a carb burner which I pretty much would have been for the 30 odd years before now.

    But on the other hand I was sort of thinking that it may the best time to consume a slightly higher carb meal as the exercise will help to moderate the insulin levels etc.

    Utimately is the 15/20/65 ratio the best ratio to strive for even in a pre-workout meal?

    Like I said I have been trying a similar ratio lately but have been hitting the wall, but I would say it was possibly a bit lower, say around 20% protien / 15% carb / 65% fat, roughly.

    This morning my pre-workout meal was more like; 30% carbs / 15-20% protien / 50-55% fat. After this I trained like a demon.

    It’s only been a few months since starting to really try to change the ratios of my diet to higher fat, do I just need to implement it slowly and gradually reduce the carbs before workouts as my body adjusts?

    Overall though by sticking to your recommended ratios and eating the recommended safe foods etc that you have outlined, my general overall feeling of wellbeing is starting to become very good at the moment.

    It’s just the training side of things I have to fine tune now, though after your advice so far and from how i felt during training today, I don’t think it should be too hard.


    P.S. I still don’t know how to start a new thread.

  10. Hi Danny,

    As an athlete you need more carbs and protein than our standard recommendation. A 30% carb / 15% protein / 55% fat mix is excellent. We usually frame it in terms of calories — for athletes, daily rations of carbs 600 calories + 100 calories/hr of training, protein 300-600 calories will maximize muscle gain and workout success. Some leucine/BCAA supplements will help also.

    Re threads – unfortunately I don’t have a forum, just the WordPress comment system. Perhaps I will add a forum.

    Best, Paul

  11. Hello,

    I read your book and really enjoyed it. I no longer crave my daily chocolate fest or dive into the fruit bowl. I’ve added sweet potatoes and yams to my diet but am having horrible gas pains and gurgling about 4-5 hours later. I read through the posts here but it wasn’t mentioned why that happens? I can easily replace with rice but love the sweet potato/yam so was just curious as to why that happens in some folks and if there was any way to alleviate this problem.

    Also,I have Hashimoto’s – in your opinion, is it best to avoid white potatoes as they are a member of the nightshades? I do eat tomatoes in season but avoid the other nightshades. Do you think that folks with an autoimmune disease should avoid the nightshade food group?

    Thank you,

  12. Hi CK,

    Different foods are digested at different places in the digestive tract — fiber isn’t digested until the colon, sugar gets digested near the stomach, other foods get digested inbetween – and you can have a different mix of gut flora and pathogens at every location. So sometimes at a particular place in the digestive tract you may have a dysbiosis that generates gas from a particular food that happens to feed that point.

    Probably in time you’ll pick up bacteria that are good at digesting sweet potatoes and yams and your immune system will beat the ones giving you trouble. In the meantime you can try probiotics, digestive enzymes, and other gut modifying steps. But I don’t know specifically what would work.

    I think white potatoes are fine. Nightshade toxins are in the potato fruit, not the tuber.

    I don’t think people with autoimmune diseases generally need to avoid nightshades, but it doesn’t hurt to do an experiment to test for sensitivity. This is done by avoiding nightshades for a few weeks, then eating a lot at one sitting.

    Best, Paul

  13. Thank you, Paul, for taking the time to answer my questions.

    I will introduce smaller amounts of Japanese yam and hope that my gut builds up the bacteria needed and go from there.

    Good to know about the potato and nightshades. I will do what you suggested.

    Thanks again. This blog is a large and very helpful source of wonderful information.

  14. Hi Paul,

    When I looked at the breakdown of sugars from the link you provided only 0.5g of the 6.5g comes from Fructose. It’s mostly sucrose and maltose – do they translate to Fructose equivalents somehow?


    Sugars 6.5g
    Sucrose 2280mg
    Glucose 570mg
    Fructose 500mg
    Lactose 0.0mg
    Maltose 3120mg
    Galactose 0.0mg


  15. Hi Mark,

    Sucrose is half fructose, so that’s 1.14 g fructose, plus 0.5 g free fructose, or 1.64 g total fructose.

  16. He said he was eating sweet potato FRIES as in fried food? Frying them in what oil?
    Could be eating loads of transfats (free radical death)
    Frying food is just dumb in my humble opinion! No fat will be free from mono & polyunsaturated fat. There will always be damage in heating oil.

  17. Relating to Robert’s problem http://perfecthealthdiet.com/?p=1848#comment-12949

    just passing along a bit of information: “Sweet potato contains raffinose, one of the sugars responsible for flatulence.” (from http://www.fao.org/docrep/T0207E/T0207E08.htm ).

  18. Thanks, Helen! These plants have so many compounds in them, it will take a lot of work to figure out all the ones that can trouble the gut. I appreciate the tip.

  19. They also contain Mannitol – a polyol that can effect those with IBS and flatulence etc.

  20. After a couple of years of gluten free (Gluten intolerance)and recovering from a massive antibiotic influx 4 years ago, I have added ‘safe starches’ in the form of rice 1 cup, sweet potato 1/2 cup and tapioca 1/2 cup to my diet in the last 3 days. This morning I could hardly stand up due to left side low back pain. Mid morning I began to have some incontinence of urine and slight gas. I didn’t see the post from Chris M until late this afternoon. I am definitely cutting out the sweet potato. Please advise. I’m ready to go back to low carb at this rate! My dry eyes and dry mouth did improve however. thanks for the help.

  21. Hi Terry,

    I would cut back all three, and try rice syrup for a bit. That’s easier digested and can give you some glucose. Hopefully that will avoid some of these problems.

    Then you can slowly introduce test bits of the starches and see if all starches give you trouble, or just individual kinds like sweet potato.

    Either way, you’ll have to fix your gut flora, but this experimenting will tell you what starches you can include in your diet.

    Then, work on the gut flora. Fermented vegetables and dairy, flora modulating foods (herbs and spices, olive oil, coconut oil), probiotics, possibly some other supplements like enzymes, colostrum, etc.

    Best, Paul

  22. I googled ‘sweet potato diet’ and it led me here. I am surprised that so many people react badly to sweet potatoes, since this (along with spinach and coconut butter) are the only foods I’ve eaten in the past 4 days (on a soft food diet for now) and I feel fantastic. My chronic back, neck, and hip pain is gone and my mind feels clearer (if that makes sense :o). I looked up oxalates and everything I read says they’re bad news, yet I feel better. Weird stuff. After reading about oxalate foods and their connection to kidney stones, though, it makes me second guess the safety of continuing to eat these foods.

  23. Hi Stacy,


    The great majority of people have no difficulty with dietary oxalates. So there’s no reason for you to give up sweet potatoes. You might do well to diversify your diet however, even if you can only eat soft foods. Potatoes and rice syrup are other possible carb sources. Eggs, raw if necessary, make a good animal food source. Yogurt might be helpful, though some people are sensitive to it.

    Best wishes and hope you enjoy the site!

  24. Dear Paul

    I’ve been following the PHD for a few months now, and with excellent results, but I’ve had a very peculiar experience with sweet potatoes that I wanted to share with you. We get white and orange fleshed sweet potatoes here where I live in Spain, and I’ve been eating a two finger thick slice of baked sweet potato every night with my bone broth for a couple of weeks (the white variety, sweeter than the orange one- approximately 30 to 40 grs., I guess).

    Then one day, I started to feel a stiff neck. I couldn’t turn my head to the left, and then I started to feel joint pain, specially in my legs, what made it quite painful to walk the full one hour I walk every day. Overall, I was feeling achy and stiff, something I had never experienced before.

    At first I thought all this was due to lack of sleep, stress and the winter cold- but the stiffness and pain didn’t go away, actually, they got worse. Then I remembered having read about the sweet potatoes and the oxalates in your blog, and decided to stop eating sweet potatoes to see what happened. It’s been three days that I don’t eat them, and I’m happy to report that the symptoms are slowly disappearing: I can turn my neck again, and I can walk on a quick and brisk pace again without feeling any pain.

    I don’t understand this at all: I’m a pretty healthy person, with no major illnesses, although since I started the PHD, I’ve come to realize maybe I have certain food sensitivities- wheat and spinach I do not tolerate well, and although I can eat certain vegetables without any problem, others simply do not agree with me at all.

    I may have to list sweet potatoes as not quite a safe starch for me from now on, because even though I was only eating a bit of it, doing so on a daily basis was definitely creating a problem.

    Thanks so much for your attention, and let me congratulate both you and Shou-Ching for having written such a great book- I wish it were translated into Spanish and published here, so that more people knew about it!



  25. Hi Laura,

    Thanks for sharing, it’s great to get case studies like yours.

    I don’t know what it is about sweet potatoes either, but some people are definitely sensitive to them. Oxalates maybe, but then we still need to understand what it is that makes people sensitive to oxalates, and whether it’s remediable.

    Well, food is likely to hold many mysteries for a long time to come!

    I hope to make a push for translations in the new year … either that or when we do a revised version of the book, probably 2013.

  26. What interested me about this post is that Chris had a stiff neck and was limping, and Lisa was very achy. These are a few of the symptoms I have been dealing with for years. I was diagnosed with fibromyalgia in 2009, improved on Savella, then plateaued, and now on the PHD for a few months, am improving almost back to where I was in my early 20’s.

    The symptoms that still persist are an achy neck that comes and goes, and big swollen painful bumps on my inner elbows. The bumps increase and decrease in size. The pain from them significantly decreased when stopping gluten, but has not gone away completely. It now only affects me during sports and lifting. I cannot curl much more than 20 lbs per arm without pain.

    I did a Google search on oxalates and fibromyalgia. I found this


    A source whose reliability I do not know how to judge, but it did reference the relation of oxalate sensitivity and candida overgrowth, mentioned in the post.

    In addition, this paper


    which I found at the suggestion of the first link. From what I understand, there is a treatment of fibromyalgia which is to give Guaifenesin, and this helps get rid of oxalate buildup. I don’t know if this is consistent with any of the viral or bacterial theories of fibromyalgia origin. Does anyone know if Guaifenesin is a reasonable treatment? Has anyone else experienced sore neck, joints, achy-ness, or stiffness, and been able to link it to any kind of oxalate sensitivity?

  27. Organic sweet potatoes are the best. keep in mind that non organic has been sprayed. There is a test done on you tube. A sweet potato sprayed with pesticides, stick in a glass of water will not grow roots or stems or branches, it is dead. An organic sweet potato will grow
    leaves, stems roots. This should be enough to prove any case on organic versus non.
    Organic codes start with a 9
    non organic starts with a 4
    Gm starts with 8
    the you tube video is called “my potato project”

  28. This Food Robs Your Brain Power – Avoid It for Clearer Thinking - pingback on January 23, 2012 at 1:31 am
  29. To Justin,

    Dr. St. Amand has a theory about guaifenesin and fibromyalgia. According to him, guaifenesin helps the kidneys to excrete phosphates. Some people have a condition where the kidneys cannot excrete phosphates so phosphates are then deposited throughout the body, primarily in muscle tissue, causing lumps and lesions. I did his protocol for a while and lesions or lumps in my muscles did decrease. I don’t have his website handy, but his book is What Your Doctor Won’t Tell you About Fibromyalgia. I hope I have that right! It’s been a long time since I did the protocol.


  30. Hi April,

    Thank you for the information. It helped guide me in doing some reading on Dr. St. Amand’s website, which was too much information for me to sort through at first. Correct me if I’m wrong, but I get the feeling that it helped you a bit, but perhaps was not really a cure. I think I will keep the idea in the back of my mind, but will not act on it yet.

  31. It is in reality a great and helpful piece of information. I’m glad that you just shared this helpful information with us. Please keep us informed like this. Thanks for sharing.

  32. I have no adverse reaction to sweet potatoes, and am wondering if korean glass noodles made from sweet potato starch are considered a safe starch?

  33. On the issue of sweet potatoes causing a negative reaction I dont know if anyone had mentioned the issue of FODMAPS and how they pertain to sweet potatoes. Fodmaps
    Or foods high in them may set off reactions in people with poor gut health. Sweet potatoes appear on the fodmap restricted list because they are high in a natural alcohol sugar called mannitol. At least that is my understanding of it. I have been treated for IBS in the past and following a FODMAP free diet is one treatment tried by GI and on the avoid list were sweet potatoes. So just some food for thought.

  34. Hello,

    I am having trouble being able to treat my hypothyroid symptoms. My endocrinologist says I am not hypo. My lab tests are normal from what he says. I do have an enlarged benign goiter/thyroid.

    I am currently experimenting w Lalonde’s recommendations for Hashimotos (autoimmune paleo).

    (Paleo Solution episode 68)

    Natasha talks about developing all of the symptoms of thyroid deficiency, but with plenty of thyroid hormones in the blood from the formaldehyde can have on the gut. She also says glucose (starch) is converted into formaldehyde and create this problem.

    (17-27 min mark. http://undergroundwellness.com/how-to-boost-healthy-gut-flora/)

    I am having trouble being able to tell if upping my carbs with safe starches (since I believe doing a ketogenic diet for too long caused my hypothyroidism) or if I simply have candida overgrowth.

    Any thoughts would be appreciated.


    (18-27 min mark)

  35. Hi Henry,

    I definitely think you should eat some safe starches.

    Candida infections can cause a mild hypothyroidism and will get worse on a ketogenic diet, so that is a possible explanation of what happened. Upping carbs would help against Candida.

    Doctors often don’t know that the “normal” range of TSH is set to include 95% of the population and that TSH of 1.5 or higher is associated with impaired health and can often have hypothyroid symptoms. It’s best if you know your lab numbers and form your own judgment.

    Have you been tested for anti-thyroid antibodies to see if you have Hashimoto’s?

    I don’t give much credence to the formaldehyde theory. There’s nothing about it in Pubmed that I can find.

    Best, Paul

  36. Paul,

    Thank you for your response. I have included more safe starches and feeling a bit better.

    Do you think it’s a problem that I’ve put on weight since upping the carbs? I feel lethargic so I don’t have much energy to exercise. It’s maybe that I’m eating too many. Guess I will have to experiment to see what are appropriate dosages.

    I will be testing for anti-thyroid antibodies asap and forming my own judgment.

    Any recommendations on getting accurate, inexpensive tests in Southern California?

    Are you a fan of squashes/pumpkins as safe starches?

    Much appreciated,

    Henry Duran

  37. Hi Henry,

    Putting on weight consistently would be a problem, but a small gain over the first few days is not. You do have to cut fat a bit so that overall calories don’t increase. If you do that then there should be no long-term weight gain.

    A good dose is 0.5 to 1 pounds of “safe starches” per day.

    I am a fan of squashes and pumpkin.

    Best, Paul

  38. Sweet potatoes give me a stiff neck also, and two year old son seems to have issues digesting them properly and may be more cranky the day after eating them. (We’re on the autism spectrum so it’s hard to say for sure where his crankiness comes from.)

    I haven’t been able to find much online about it. I buy our sweet potatoes from Whole Foods mostly, though ones from another store do bother us too. No other food that I know of causes this reaction, and we eat plenty of berries.

    I’ll try checking for any signs of damage next time and see if it changes the effect. I’ll give it one last shot.

    Also, I have mild psoriasis – one large patch on my lower leg. Thank you for your detailed posts about angiogenesis. I stopped DHA supplementation and my leg is healing finally! Every time I eat a 1/2 lb of salmon over the course of two days, it feels very itchy for an hour. If I eat more salmon than that or for three days straight, the psoriasis flares and stays flared up for several days. I think you’re just about right with the one pound a week recommendation. Of course n=1 here.

    Overall, we’ve had a lot of success with your diet. More improvements to make, but I really appreciate you guys taking your time to put together and provide this information for others.

  39. after reading this article and a few other pages, i have decided to completely eliminate sweet potatoes from my diet.

    every time i eat one, it feels like it just “sits” in my stomach for hours on end. plus, it makes me bloated and uncomfortable feeling.

    my main sources of carbs come from the following foods:


    what is another whole-food carb-source that is easily digested?

  40. What if the problem with sweet potatoes was actually their ANTIMICROBIAL properties?

    “One of the more intriguing nutrient groups provided by sweet potatoes—yet one of the least studied from a health standpoint—are the resin glycosides. These nutrients are sugar-related and starch-related molecules that are unusual in their arrangement of carbohydrate-related components, and also in their inclusion of some non-carbohydrate molecules. In sweet potatoes, researchers have long been aware of one group of resin glycosides called batatins (including batatin I and batatin II). But only recently have researchers discovered a related group of glycosides in sweet potato called batatosides (including batatodide III, batatoside IV, and batatoside V). In lab studies, most of these sweet potato glycosides have been shown to have antibacterial and antifungal properties. To what extent these carbohydrate-related molecules in sweet potatoes can provide us with health benefits in these same antibacterial and antifungal areas is not yet clear. But we expect to see increasing interest in sweet potato’s batatins and batatosides and their potential to support our health.” (From World’s Healthiest Foods website)

    I have known dysbiosis issues, and I had overall stiffness, achiness, and soreness eating sweet potatoes, so I stopped and it went away. I didn’t have any more problems until I tried preserved lemons (whole lemons – rind and all – cured in salt). Suddenly the whole body stiffness was back. Lemon rinds are highly antimicrobial (see http://www.pakbs.org/pjbot/PDFs/41(6)/PJB41(6)3207.pdf)

    Is the problem possibly the result of an overload of toxins from the death of large amounts of gut flora?

    Just guessing here, but it looks like this is a real possibility.

    • Hi Laura,

      Intriguing idea. I’m inclined to doubt it, but it would be great if that were the case. If it is antimicrobial effects, then eating them with charcoal would reduce the symptoms.

      • I actually just read that lemon rind was high in oxalates. If you think it could be the antibacterial effect just eat a crushed clove of garlic to see if the same thing happens. I’ve eaten many antibacterial foods as such and they do not reproduce the pain I get from sweet potatoes.

        They give me a back pain that is different than my normal back pain from overuse or whatever. It is more debilitating and gets much worse with using those muscles or bending different ways. I could pretty much stay in one position with no pain, but when I start to move it certain ways I feel like a 90 year old man (I’m 27). Just had the same pain yesterday and linked it to the sudden splurge of 50/50 spinach (high oxalate) and spring mix for the last 4 or 5 days. Picked out all the spinach and ate the spring mix today and the pain is 90% gone. The pain goes away 1-2 days after stopping sweet potatoes too.

        Point is it’s a very unique pain different than any others I have experienced, but I am prone to back pain. Oxalates supposedly crystallize in damaged tissue and multiply the damage, inflammation and therefore pain.

        I am also very sensitive to msg for example in bone broth cooked a long time. My heart races for hours along with a cracked out head that will not allow sleep. I believe both msg and oxalates are more of a problem when one has leaky gut. I’m pretty sure I have that considering these problems and other digestive issues, so fixing that may be an answer- or at least help?

  41. Could it be vitamin A/beta caronene? 1 cup has 769% us rda.

  42. Paul,

    I know that potatoes and sweet potatoes are high in oxalates. But what about yams? (I mean true yams, not the sweet potatoes that people call “yams”).


  43. Would the Okinawan type (purple inside) classify as a sweet potato or a yam?

  44. Not sure we can get true yams in the U.S.
    (my 1st post—considering trying the PHD)

  45. is high maize resistant starch safe

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