In his book the Plant Paradox, Dr. Steven Gundry sounds the alarm on the danger of lectins as the source of a wide variety of ailments plaguing our modern world, but some aren’t buying it.
What are lectins and why are some in the nutritional community so skeptical of Dr. Gundry’s theories?
What are lectins?
Lectins are carbohydrate binding proteins, found in plants, which are thought to act as defense mechanisms against predators. Plants don’t want to be eaten, they want to sprout and grow, and they developed lectins as defense shields, or so the thinking goes. The theory is not without scientific merit. Many plant lectins do indeed breach the gut wall of the insects that eat them and in so doing demonstrate strong “insecticidal activity.” (R) Dr. Gundry believes lectins induce the same inflammatory response in the human gut.
He argues we should do our best to reduce exposure to lectins in our diets as they may be the culprit behind some of the strange and inexplicable autoimmune conditions that seem to be popping up everywhere these days.
Because lectins are so widespread, and because they are found in what are thought to be the healthiest foods, Dr. Gundry has received a lot of blow back for advancing his theories. For example, tomatoes are full of lectins. Are we really going to have to stop eating tomatoes now?
What will be left to eat?
And that’s one of the main arguments I hear against implementing Gundry’s protocols, they are very restrictive. The Plant Paradox program excludes all grains, nightshades, most dairy (except some goat and sheep dairy) and almost all beans unless they’ve been prepared in a pressure cooker. Think you’ll fall back on chicken? Think again unless you can verify Portlandia style that it’s been pasture raised.
It’s a good thing that Dr. Gundry has been met with skepticism. There are simply too many nutrition theories out there. One like this, which if true has wide reaching implications for how people eat, should be laughed out of court if there isn’t data to back up the claims. But that doesn’t seem to be the case with Gundry, he does have some published data and he isn’t saying all people need to be on his protocol, just the sensitive among us.
Altered gut microbiome drives lectin sensitivity
Is it likely that everyone is sensitive to dietary lectins? No, it’s not likely, but Dr. Gundry isn’t making panacea claims. His essential argument is this: if you’re sick with one of the growing number of autoimmune conditions we face in this country, tired, achy, or just underperforming, lectin is one area you may want to examine. And here’s the thing: Dr. Gundry isn’t easily dismissed. He’s a Yale graduate, and brilliant heart surgeon who has done some incredible things in his career, including cross species heart transplants (yes, you read that right). Link to his bio here.
His basic case is that many people can no longer digest lectin because the modern world has devastated our intestinal flora. This seems like a logical theory to me. Just a few days ago I had a conversation with a friend who has had a horrible time getting rid of recurrent yeast infection, a condition she traces back to starting birth control in her late teens.
Add to the list of medications we take the presence of toxic chemicals in everything from cookware to mattresses, and the rise of GMO crops sprayed with known carcinogens like glyphosate, it’s not unreasonable to assume some people might not be equipped with the microbes to properly digest certain lectins. Lectins are controversial, but increased pollution, prescription medications and widespread use of antibiotics seems to be changing the shape of our microbiomes. In his paper, Do Dietary Lectins Cause Disease, allergist David L.J. Freed theorizes that a serious infection could be the triggering event that alters the microbiome in such a way that we become prone to lectin sensitivity and certain autoimmune conditions.
The altered microbiome theory is gaining traction as consensus fact, and it’s imbalances of the gut that drive Gundry’s claims about lectin. Some have cast him as an outsider, but he’s right in the mainstream of functional medicine. He argues that many people are so used to low levels of inflammation caused by lectin that a state of reduced performance is their “new normal.” But even assuming that a large percentage of the population thrives on lectin, that doesn’t mean we all do.
For example, could a C-section birth, which is thought to be deprive babies of important foundational microbes, combined with a serious infection and a few rounds of broad spectrum antibiotics be just what the doctor ordered for a problem with digesting lectins down the road?
Dr. Gundry has been around for awhile, but I am just now sitting down to do the research, and I must say I was surprised at some of the science that is out there on lectin sensitivity. To be fair, it’s certainly not overwhelming, but there are legitimate reasons to be wary of lectin. Below, I run through some of the major discussion points.
Lectins travel to distant organs
I was surprised to learn that studies in rats have shown lectins have the ability to get passed the gut wall and deposit themselves in distant organs. (R)
One of the reasons Gundry recommends avoiding commercial poultry is that the animals are fed grain, a high lectin food. He believes some of his more sensitive patients react to factory farmed chicken because the lectin from the grain feed remains in the bird’s flesh even after it’s slaughtered. Of course, I suspect antibiotics and toxins like arsenic may have something to do with the problem as well, but the lectin angle is fascinating.
There is even some evidence that lectins can travel to the brain. This study is footnote #5 in the Plant Paradox, and it demonstrates (albeit in a worm model) that lectins can travel from the gut to the brain by way of the Vagus nerve where they impact the function of neurons, offering an alternative theory on the cause and development of Parkinson’s disease.
Again, the study cited by Gundry is a worm model, and it’s on the frontier of nutrition science, but nonetheless, there are other papers that show benefits to mental health when removing grains, so it’s something to experiment with and keep in mind when testing out theories behind anxiety for example. This Danish study showed a 40% reduction in Parkinson’s disease in people who had their Vagus nerve removed.
I am a sample size of one, but for what it’s worth, I feel significantly calmer when I eat grain free for a number of consecutive days.
For more, check out Frontiers in Human NeuroScience: Bread and Other Agents of Mental Disease.
To quote the paper:
A grain-free diet, although difficult to maintain (especially for those that need it the most), could improve the mental health of many and be a complete cure for others.
This article from Psychology Today titled “Are Grains Destroying Your Health?” is also worth a read.
Lectins and heart disease
Peanut oil is high in lectin. In a study titled “Lectin may contribute to the atherogenicity of peanut oil,” researchers found that when lectin was reduced in peanut oil by washing, incidence of heart disease dropped significantly in animal models (mice, rabbits and primates). (R)
Then there is this tiny study which was authored by Gundry in which he shows reversal of endothelial dysfunction for patients who avoided major dietary lectins, stopped eating commercial poultry (also a downstream source of lectin as they are fed grain), ate a Mediterranean diet rich in leafy greens, and supplemented with a regimen of nutrients like pycnogenol and fish oil. At the beginning of his study, 76% of a group of 200 (120 men and 80 women) had endothelial dysfunction. After 6 months, only 20% still had endothelial dysfunction.
The thing about Gundry’s arguments regarding plants and heart disease is they may focus on the wrong culprit. The evidence for lectin and heart disease isn’t overwhelming, but there is better evidence that those who are heavy absorbers of sterols (the fats in plants) may be at increased risk for heart disease. (R) For example, we do know of a rare, but perhaps under diagnosed condition called sitosterolemia that is marked by an inability to clear plant sterol from the blood resulting in accelerated heart disease, sometimes in children. (R) Sitosterolemia is associated with mutations in the ABCG8 genes. However, even when the major sitosterolemia SNPs aren’t present, it is possible that certain people aren’t as effective at clearing sterol as others which could lead to heart disease over time. Perhaps reduced ABCG8 function operates in a similar fashion to reductions in urea cycle function which fall short of a diagnosable illness and instead cause a diminished, but functioning metabolic ability.
Lectins can break down the gut wall
Wheat contains lectins that cause celiac disease and gluten sensitivity in growing numbers of people. I have written previously about labs I had done to rule out celiac disease. While I did not have the classic elevated transglutaminase IgA markers indicative of the disease, I did have elevated tTG 2 IgG antibodies, which tends to suggest a poor reaction to wheat. I did not have a biopsy of my small intestine done, but I have read of cases where an endoscopy was performed on tTG IgG patients and damage to the small intestine was found. It is an accepted medical fact that wheat proteins can cause severe damage in some people.
Wheat proteins do us harm by attacking the gut lining, making the barrier between our intestines and the inside of the body more permeable, which for some, can lead to symptoms ranging from digestive issues to achy joints to problems with mental health. (R) Zonulin, a protein which can break apart the “intracellular tight junctions” of the gut wall, is produced when we eat wheat. The theory of leaky gut is that the resulting intestinal permeability lets all sorts of bad guys into our blood stream and the immune system goes wild as a result. (R) One of the most successful dietary interventions used to treat Rheumatoid Arthritis is a gluten free Vegan/Vegetarian diet. Of note: some of these RA diet studies have found an “association between disease activity and intestinal flora indicating impact of diet on disease progression.”
Removing wheat is becoming a standard practice for treating Rheumatoid arthritis and we know it’s a must for those that are gluten intolerant.
What about other plant lectins?
Can they breakdown the gut wall in the same way that gluten does?
Yes, to kidney beans. Kidney bean lectins have been shown to facilitate growth of E. Coli in the small intestine. (R) The lectin in oats can’t be destroyed by pressure cookers and have an inflammatory effect for many people. (R)
But then you have evidence of anti-carcinogenic activity by certain soy lectins, a food that is on many people’s avoid list, so it’s not like we have an open and shut case. (R)
Gundry argues wheat is just the beginning. That many other species of plants contain similar proteins, which may be benign in comparison to wheat, but which can also cause us harm over the long term. Yes, his theories are not proven!
BUT, as long as people continue developing mysterious autoimmune conditions at the pace they are in today’s environment, it’s worth a look.
What about the Blue Zones?
Vegan advocates really don’t want you to follow Gundry’s diet advice because he advocates for eating small amounts of high quality meat and fish, but not too much so as to keep IGF-1 levels in check. After all, if the Plant Paradox has validity, the simple message of “everyone would be healthier on a Vegan diet in every instance,” begins to look dubious, and the marketing machines behind these diets can’t have that, so they all started attacking Gundry. One of the most notable was Dr. Greger of Nutrition Facts. In his video titled “The Plant Paradox is Wrong,” Greger rips Gundry as advocating for the discredited blood type diet, with one little problem: the blood type diet has not been totally discredited.
Next, he goes to the Blue Zones (communities where people routinely live to be 100 years old), where he’s on stronger footing. It is true, those who live in Blue Zones consume a lectin heavy diet, with beans as a cornerstone. This has been well documented by researchers like Valter Longo and Dan Buettner in their respective books The Longevity Diet and Blue Zones. However, Longo, whose work I love, recommends “eating at the table of your ancestors”and to avoid foods that your “tribe” hasn’t traditionally eaten. Longo advocates for a largely plant based diet, but also advises readers to identify and steer clear of food sensitivities. To quote Longo:
Whether it’s lactose or kale, quinoa or curcumin, you have to ask whether these were foods common at the table when you, your parents, or your grandparents were growing up. If not, it’s best to avoid them, or consume them only occasionally. The potential problems are intolerances or autoimmunities, such as the reaction to gluten rich foods like bread and past observed in people with celiac disease. Although clear links have not been proved yet, it is possible that consumption of the wrong foods based on ancestry could be associated with many autoimmune diseases, including Crohn’s, colitis and type 1 diabetes.
Hmm, sound familiar? And yet, Longo is a darling of the nutritional world where Gundry has a target on his back. In essence, they are saying the same thing! Gundry doesn’t tell readers to avoid beans, he just suggests cooking in a pressure cooker to destroy lectin count.
As far as the Blue Zones are concerned, I see the fundamental difference as the microbiome. The Blue Zone communities have been living in the same manner, eating the same foods for generations. They are “off the grid” of the industrial food system and therefore have not had the same assault to their intestinal flora that we in modern cities have suffered. In short, they could be in a better position to consume and digest lectin. Regardless, each of these communities have food preparation methods aimed at reducing lectin. You better believe the beans they eat are soaked and slow cooked.
Greger then cites studies demonstrating the positive health benefits of tomato juice, and yet, tomato lectin lives primarily in the seeds, so processed tomato products like juice have had their lectin removed.
Perhaps the most damning argument Greger pulls out against Gundry is the existence of his supplement line, which I can’t defend. It is tacky to write a book warning about lectin and then launch a “Lectin Shield” product.
Closing thoughts – not proven, but plausible
No two people respond to a given food in exactly the same way. I can eat a peanut and feel fine, others will go into anaphylactic shock.
The same is probably true for lectins. On the dark side, Gundry’s book creates even more anxiety around food, which isn’t needed in today’s climate. Many people probably don’t need to avoid lectin.
Having said that, orthorexia begins where the substantive benefits of dietary intervention stops, so it’s not neurotic to exclude foods that have a confirmed deleterious impact on our health and wellbeing. Some people don’t do well eating grain, others thrive. In these cases, it’s not helpful to cite nutrition questionnaire studies and say “but 86% of respondents over a 22 year period had 12% fewer incidents of joint pain when eating 35% more fruits and vegetables.”
I am so tired of that BS.
If your body feels better avoiding oats or beans, don’t eat them. You have a basis in fact for doing so.