How Do Grains, Legumes and Dairy Cause a Leaky Gut? Part 1: Lectins

March 22, 2012 in Categories: , by

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(Created as a guest post for The Paleo Parents)

One of the fundamental principles of paleolithic nutrition is to protect the lining of the gut by eliminating foods that damage it.  By prioritizing gut health, we are able to treat and prevent the many health issues associated with having a “leaky gut”.  But how exactly do grains, legumes and dairy wreak so much havoc on the digestive tract?  There are several ways in which these foods create holes in the gut lining.  The best understood is the damage caused by lectins.

Grains and legumes contain lectins.  Lectins are a class of proteins found in many types of seeds (like wheat, oats, barley, rice, peanuts, soy, etc.) that are part of the plant’s natural defense mechanism.  A digested seed is not one that can grow a new plant.  To defend itself, the seed from these plants either deter predators (like us) from eating them by making us sick or resist digestion completely or both.  The grains and legumes that have become a part of the human diet since the Agricultural Revolution 10,000 years ago aren’t toxic enough to make most of us severely ill immediately after eating them (otherwise humans never would have domesticated them!).  Instead, their effects are more subtle and can take years to manifest as a life-threatening disease.  You may be wondering why other seeds (like the ones in berries or kiwi or bananas) are okay to eat.  These come from plants with a friendlier defense strategy:  we get to eat the delicious fruit encasing the seeds and then the seeds, which pass through our digestive tracts intact, get to be planted in rich manure.  How do you know the difference between a harmless seed and one that contains damaging lectins?  Here’s the rule:  if you can eat it raw, then it’s okay to eat.  If you have to cook it, it has damaging lectins. 

Lectins are not broken down in the normal digestive process, both because the structure of these proteins are not compatible with our bodies’ digestive enzymes but also because the foods that contain these lectins also contain protease inhibitors (compounds that stop the enzymes from breaking down proteins; more on these in Part 2).  Lectins, which remain largely intact throughout the digestive tract, can damage the gut lining in several ways.  First, lectins trick the enterocytes (the cells that line the gut) into thinking they are simple sugars.  The enterocytes “willingly” transport the lectins from the “inside-the-gut” side of the cell to the “outside-the-gut” side of the cell.  While in transit, the lectins may cause changes inside the enterocyte that either kill the cell or render it ineffective at its job, which leads to more pathogens leaking out of the gut.  Once outside the gut, these lectins activate the resident immune cells of the gut which respond by producing inflammatory cytokines (the chemical messengers that circulate in the blood and tell white blood cells to attack) and antibodies against these foreign proteins.  Because at least part of this response is not specific to the lectin itself, the enterocytes (being the closest innocent bystanders) can be targeted and killed by the body’s immune cells, leading to the microscopic holes that create a leaky gut.

 Gluten is both the best known example of a lectin, and also the most damaging.  In many individuals (like those with diagnosed gluten sensitivity and celiac disease), gluten can weaken the connections between enterocytes, essentially creating a space in between the cells through which gut contents can leak through, adding yet another way that this particular lectin can cause a leaky gut.  Once gluten has passed through the gut lining, it stimulates the resident immune cells of the gut to start producing antibodies.  Gluten is especially insidious because parts of this protein closely resemble many proteins in the human body, so there’s a high likelihood that some of the antibodies produced to target it will also target human cells.  One extremely commonly formed antibody is one against our enzyme transglutaminase.  Transglutaminase is an essential enzyme in every cell of the body, which makes important modifications to proteins as they are produced inside the cell.  It also stimulates wound healing, but if antibodies have formed against it, then when it is secreted by damaged cells in inflamed areas of the small intestine (or any other damaged tissue in the body), rather than helping to heal the surrounding tissue, it instead turns it into a target of the immune system.  This is yet another way in which gluten can cause a leaky gut.  Importantly, when antibodies against transglutaminase form, every cell and organ in the body becomes a potential target.  Because an exaggerated sensitivity to gluten is the cause of Celiac Disease, which affects at least 1 in 133 people, its effects on the gut have been the most studied.  Scientists still don’t know which of the many ways that gluten can harm the body apply to all lectins and which are specific to gluten.

Gluten sensitivity has already been linked to dozens of autoimmune diseases.  Even in individuals who do not have celiac disease or gluten sensitivity, it can take up to six months for the gut to fully heal after a single gluten exposure.  While other lectins may not be quite as damaging as gluten, scientists continue to discover new ways in which foods that contain lectins can contribute to a leaky gut, inflammation and autoimmune diseases.



At last an explanation as to my PERCEPTION that even rice–which all the leaky-gut “experts” told me was okay–isn’t at all. And it explains why if I happened to eat a somewhat different form of rice or some other “safe” grain, it was as if I had been hit by a train. I’m combining this info with the excellent info on leaky-gut (and why acupuncture has FAILED ME) by Dr. Jake Paul Fratkin of Boulder, Colorado, combined with probiotics, an anti-viral (since I have high levels of Epstein-Barr), plus I’m finding an D.O.M. willing to use Fratkin’s approach to acupuncture. By the way, my leaky gut–likely hovering around the edges much of my life–is, I am sure, the product of heavy, heavy anti-biotic exposure as a child. One doctor even kept me on them when I was well, hoping to keep me from catching the next cold, absurd, since colds are a virus and antibiotics don’t fight viruses. But it makes me wonder how many people are out there as sick as I am from what I’m calling “dead gut syndrome,” or a digestive tract very nearly destroyed by modern medicine and made worse by my New Mexico doctors (mainstream AND alternative) who either won’t admit it exists or don’t know how to treat it!

Your posts are clear, easy to understand and extremely beneficial – I have been looking for a good synopsis on leaky gut and I found it here!! Thank you for your great work!!

This is awesome, but there are doubters a-plenty in my extended family (how can grain be bad for you if it’s in the bible?) Can you cite your sources? Thank you!

I can definitely add some references for this when I get a chance. My suggestion for a great place to start is Prof. Lorain Cordain’s The Paleo Answer. He has meticulously researched every aspect of the rationale behind a paleo diet and cites thousands of research articles to back up his case. I would also direct you to the research of Prof. Mat Lalonde at Harvard and Dr. Alessio Fasano at University of Maryland, both of whom have done outstanding work in this area.

You talking about dairy, how about organic grass-fed milk? and is it safe/safer to eat the grain if you sprouted it first or soak it for at least 24 hours before cooking? I would love to hear back from you.

I was diagnosed with a leaky gut a number of months ago after having a severe chronic fatigue crash and escalating gut symptoms (aweful reflux, gallbladder symptoms with no detectable gallstones on ultrasound). Anyway, the reflux is coming back, it’s so so so distressing.
Anyway, your explanation was really helpful! I’m going to keep reading!
After IgG tesing can’t eat dairy, egg whites or nuts and I already knew I couldn’t tolerate gluten. It’s interesting that seeds/ lentils etc aren’t so good. I’m feeling a little stressed about what to eat, I wanted to go vego, but it looks like this is not the time to do so. Sorry, needed to rant.

You are totally allowed to rant! I wish a doctor had told me about leaky gut when I first started having symptoms about 5 years before autoimmunity symptoms started. It would have saved me alot of strife! I eat meat, fish, non-starchy veggies and fruit. I still manage to find lots of variety and feel very satisfied with my meals, but it does take a little trial and error to figure out what is sustainable for you. Good luck!


I like your blog a lot, haven’t read a lot of it but from what I have, it looks very good!

I just have a question? In this article ( you talk about eating seeds, but now I’m a little puzzled… :)

In this article you explain that seeds often contain lectins, which lead to explained symptoms. Why is it that some seeds don’t contain them? And how to distinct between both, eg cooking vs raw?

Thanks in advance!

Kind regards,

I will definitely write up the answer to this question in an upcoming post. Basically, all plants contain lectins. There are many different kinds of lectins and some are more damaging than others. Lectins in plants that you have to cook before you eat (like soy, wheat, rice, peanuts) tend to be much more damaging to the human digestive tract. So the rule of thumb is that if you have to cook it to eat it, it’s not safe. If you can eat it raw (you don’t have to), then it’s okay. That is why seeds and nuts are okay in small quantities (they still tend to be high in omega-6 fatty acids which makes them not the best food). I hope this helps!

I’m also interested in your source for the statistic regarding it taking six months to heal from one exposure to gluten. Thanks for your help!

Thank you, Sarah! I’ve seen this range mentioned before but was wondering where the statistic came from! LOVE YOUR BLOG!!! Am sharing it like crazy today on Facebook. Sounds like there are some other addicts out there.

Well in a way looks like nice article and there are good points,though statement ” gluten is lecithin” is a total crap! gluten is a protein found in most grains and probably is pretty unhelthy for us, but it has nothing to do with lecithin. Lecithins are usually phospho-lipids with certain chemical properties that are in no way related to those of gluten, regrdless of toxic properties of some of them.FYI eggs contain huge amounts of lecithin.NOT ALL OF THEM ARE BAD. So I think you should not spred false information just to promote the paleo diet, it is int he end contraproductive. And go learn about that stuff before you write more misinformation.

Failing to see where I call gluten a lecithin. This post is about lectins which is an entirely different class of proteins than lecithins. You are right that lecithin is only problematic in high concentrations. And actually, you’re statement of “not all of them are bad” applies to lectins as well. One of the nuances of lectins that is not properly discussed in this post is that many are inactivated by heat and many interact so weakly with the glycocalyx layer that they can not enter the body. For this reason, I go into far, far more detail about subtypes of lectins (mostly prolamins and agglutinins) in my book (those sorts of details are hard to distill in blog post format).

here: ” Gluten is both the best known example of a lectin, and also the most damaging. In many individuals (like those with diagnosed gluten sensitivity and celiac disease),..”
And I am implying again – LECITHINS ARE NOT PROTEINS and also I didn’t say high concentrations I said different types.

Right… it says lectin. not lecithin. Lectins are carbohydrate-binding proteins with fairly complex quaternary structures. Gluten belongs to a sublclass of lectins calles prolamins. Lectins are something completely different from lecithin and you are right, gluten is not a lecithin.

Will there be information about lectins in foods allowed in AIP also and how they interact with glyconutrients and how heat treatment effects them ? For example I experimented with raw pumpkins a while and found it gave me joint pains, I started to consume them cooked and I didn’t have joint pains years ago and the reason must be the inactivation of pumpkin lectins which bind glyconutrients, probably n-acetyl-d-glucosamine. Also, note that some plant lectins are aggravated with heat, such as nightshade lectins.
The most complete free information I could find about it is probably this one:‎
And the most complete information about it may be in this book:
But even the book doesn’t give information on how heat treatment effects different lectins.
I bought you book with a Amazon Prime trial which gives free shipping for 30 days and I want to buy a book about lectins and glyconutrients in food and how heat effects them also if your book doesn’t give the information. Can you suggest a source of information about it ?

I’m up early this morning, enjoying your blog, and I have to say that I tip my hat to you for responding to Sandra in such a professional manner. :) Respect!

Excellent post! What really caught my attention here, was the bit about how gluten can affect wound healing. My other half takes weeks to heal even small wounds and there is no other reason found for this, such as diabetes or zink deficiency. Still waiting for your book to arrive, but once it has, it will be a strict AIP kitchen in our house! Keep up the good work by the way. Your wealth of knowledge is so valuable… Much love, Angel xxx

[…] of them!) , but has yet to pervade medical practice (like so many nutrition-related health issues). How Do Grains, Legumes and Dairy Cause a Leaky Gut? Part 1: Lectins. (Created as a guest post for The Paleo Parents) One of the fundamental principles of paleolithic […]

[…] is made even worse by two other compounds found in these foods: saponins and protease inhibitors. How Do Grains, Legumes and Dairy Cause a Leaky Gut? Part 1: Lectins. (Created as a guest post for The Paleo Parents) One of the fundamental principles of paleolithic […]

[…] Lectins are a sugar-binding protein contained in all plants, protecting them against predators. There is variability in the effect of different dietary lectins have on our digestive system, ranging from pro-inflammatory (e.g. promotion of a leaky gut) to completely harmless (e.g. therapeutic properties). Similar to zonulin, the pro-inflammatory variety of lectins (e.g. nightshades, legumes, dairy, grains) inhibit proper digestion by allowing toxins and undigested food particles to be transported across the intestinal tract. This in turns causes the body to trigger an autoimmune response and attack these pathogens as foreign bodies. For more detail on how lectins impact digestion refer to this in depth post: […]

thanks paleomom. great info and so easy to digest. any idea why the asian population who lives on rice seems to do so well on a lectin diet?
are eggs good or bad for us, i though you said somewhere free range eggs are ok ?

Saw your presentation on the For Women Only Weightloss… Conference and have come to glean more info from your blog. Thank you for all the time and energy you have committed to sharing your expertise and research.

The burning question that can’t wait until your book arrives: where do beans fall in a diet for someone just now showing evidence of Hashimoto’s?
I love beans, corn tortillas, and calabasitas (mixture of zucchini, yellow squash, onions, cheese) but have deleted them from my diet–save the squash–for over a month now. I’ve read that if soaked at a given temperature for 18 hours, rinsed twice during that time, then cooked, the “bad” lectins will be diminished up to 70%. Does that even matter for those of us with minor autoimmune troubles?

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