What Are Lectins and Are They Bad for Me?
A book, The Plant Paradox, claims that lectins are a molecule hiding in healthy foods making you sick—is it true?
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Recently, before having a friend over for dinner, I asked him if there were any foods he couldn’t eat.
I’m someone with a longer-than-most list of dietary restrictions. I’m vegan with a soy allergy, and I’ve struggled with acid reflux, so I try to avoid spicy and highly acidic foods, like tomatoes and lemons. Point being: I’m very empathetic of dietary peculiarities, and wanted to make a meal that we could all enjoy without concern.
Then my friend started to list the foods he couldn’t have, in a meandering way, as if there were so many he couldn’t even remember them all: no beans of any kind, no nuts, no peppers, no tomatoes, no squash, no fruits with seeds—actually no produce with seeds at all—and no brown rice or whole grains.
I don’t pause anymore when people tell me they’ve given up gluten or nightshades for one reason or another, but I found this litany of foods pretty shocking. Not only were there so many of them, but they included, what I thought, were the healthiest foods one could eat. So much for the whole grain bean enchiladas I was planning to make.
My friend was following a lectin-free diet as advised to him by his doctor, by way of a book published last year called The Plant Paradox. Written by a former cardiac surgeon, Steven Gundry, the book says that lectins, a protein found in plants, were the root cause of many of our chronic illnesses and weight gain.
Gundry lists in his book, on multiple pages, all the disorders that could come about from lectin activity in the body, including autoimmune disease, diabetes, chronic fatigue syndrome, IBS, memory loss, migraines, heart disease, depression, and many more. The way to counter this is, like in my friend’s case, a diet that reduces or restricts “grains of all kinds (especially whole wheat), beans and legumes (especially soy), nuts (especially almonds), fruits and vegetables (eggplant, tomatoes, potatoes, peppers, etc.)” as well as “dairy and eggs.”
“The more fruit I removed from an individual’s diet, the healthier he or she became and the more his or her cholesterol numbers and markers for kidney function improved,” Gundry writes. “The more I removed vegetables that have lots of seeds, such as cucumbers and squash, the better my patients felt, the more weight they lost, and the more their cholesterol levels improved.”
He continues to say that removing grains (and all pseudo-grains, like quinoa, buckwheat), all legumes, tofu, edamame, and soy products, showed similar effects: “My patients experienced even greater improvements. Their cancers regressed or disappeared—yes, you read that right—as did their type 2 diabetes, coronary artery disease, fibromyalgia, and auto-immune diseases,” the book says.
I’m skeptical of any diet that claims to cure cancer, and so I wanted to learn a bit more about what lectins were and if they were doing anything to me. I called up David Katz, the founding director of Yale University’s Yale-Griffin Prevention Research Center and immediate past-president of the American College of Lifestyle Medicine, and asked him: what is a lectin?
He tells me that lectins aren’t just one thing, but are a large family of protein compounds. What makes them alike is that they’re sticky: they can bind to other molecules, usually carbohydrates. “The case made in The Plant Paradox is that the binding of lectins from plant foods to our cells is a major cause of ill health, and thus we must all fear and avoid lectins,” Katz says.
Let’s be clear: lectins can be bad for you. Eating beans raw or undercooked will lead to pretty nasty digestive symptoms, and has caused cases of food poisoning-like outbreaks. The problem is easy to solve, though. If you cook your legumes (which is more enjoyable than breaking your teeth on hard rock-like beans), it deactivates the lectins in them. And if you, like many people, buy canned beans, the canning process brings the beans to such high cooking temperatures, the lectins really can’t do you any harm.
Katz says that despite knowing that, he dipped into the peer-reviewed literature when The Plant Paradox first came out, to see if there could be any more harm he hadn't heard about. “In an unbiased fashion, I just searched lectins and health effects, lectins and cardiovascular, lectins and gastrointestinal, lectins and cancer, and so forth,” he tells me.
He says he did find a few papers that show that lectins could be damaging, because of their potential for toxicity (like in raw beans). But those papers were usually done in animal models and with high doses of lectin protein molecules, isolated on their own.
"And for every one of those papers, I found more suggesting potential benefit," he says. "If you—without bias—search Medline for studies of lectins and health effects, you find, at worst, some very provisional hints of potential mechanisms for potential harm, and a greater volume of provisional hints of potential benefit. How that translated into ‘don't ever eat beans or fruit or nuts or almost everything that's good for you’ is almost unfathomable.”
Katz says that looking at the effects of lectins in isolation doesn’t make a whole lot of sense, nor does concluding that cooked kidney beans are dangerous because raw ones are. (Raw chicken is also risky, but it doesn't mean cooked chicken is). “One of the great recurring fallacies of this sort of nutrition guru wannabe is the conflation of the part for the whole," Katz tells me. "I found something in a food that could be toxic; therefore, the food must be avoided. It's bad for you.”
He gives the example of oxygen, which is present in our atmosphere. Oxygen is highly toxic, and if you breathed it pure, it would definitely kill you. So should we refuse to breathe?
"Even if we allow for the possibility that lectins could be harmful, the foods that contain them confer benefit," he says. "Just like oxygen can be harmful, but breathing's still a good idea. What happens to people who eat fruits that contain seeds? What happens to people who eat nuts? What happens to people who eat beans? Well, they tend to live longer and have less chronic disease than people who eat french fries, hot dogs, hamburgers, and pizza instead.”
Katz is referring to the longevity and health of people who live in The Blue Zones, or areas of the world where people live the longest lives, as documented by National Geographic Fellow and journalist Dan Buettner. He found a diet heavy in beans was one of nine healthy lifestyle choices made by the world's longest-living people.
I reached out to Gundry for comment, and he responded via email with a counter to many of Katz's points. He says he agrees that cooking and soaking does help to reduce lectins, but studies he's seen show that cooking and soaking don’t inactivate all lectins. He says that in gluten, the lectins are heat stable. “I make it very clear that cooking and soaking helps to reduce the lectins in troublesome foods like beans and grains,” he tells me, but says that you need to cook them in a "modern pressure cooker" to do so.
Gundry also says that he thinks that, in the groups in the Blue Zones, the harmful effects of cereals and beans are compensated for by the other beneficial effects of their diets, and says that these diets are lower in whole grains, instead emphasizing white rice (like in Asian countries). To him, this is evidence that our focus on whole grains is contributing to our bad health. “Over the last 50 years, we have introduced whole grains into all of our prepared and processed foods, where formerly they had been removed," he says. "Perhaps the question asked should be: was the recent re-introduction of whole grains into our diet the cause of our mounting health crisis?”
But Fred Brouns, a professor of health food innovation at Maastricht University in the Netherlands who studies whole grains, says we need to be careful about the associations we make. In a 2013 review, Does Wheat Make Us Fat and Sick?, he wrote: “It is certainly true that the increase in wheat sales has a parallel with an increase in obesity. However, there are also parallel increases in the sales of cars, mobile phones, sports shoes, and the average speed of winners of the Tour de France. Similarly, a correlation between the national consumption of chocolate and the number of Nobel Prize winners has been reported. However, it is not valid to consider these correlations as causal relationships, and in the examples listed above any such claim would be ridiculed.”
He also notes that humans have been consuming wheat much longer than recent increases in obesity and its related diseases, increases which are taking place in Asian countries despite the fact that they don't eat a lot of bread or wheat.
Gundry had told me that while you could cook beans, gluten (another lectin) was heat-resistant. But in a controlled study from 2004 that Brouns referred me to—one of the only that looked directly at this question—a group found that heating pasta “greatly” affected the activity of lectins. Cooking it would result in “the inactivation of WGA," which is an acronym for wheat germ agglutinin, the lectin protein present in gluten. The researchers concluded that most cooking practices would eliminate WGA activity in pasta, if it wasn’t done so already by the processing of wheat into pasta.
“You can see that upon heat treatment the lectin activity is completely gone after cooking, which makes them a component that can not cause any harm anymore in the gut,” Bourns says.
And Bourns tells me even though Gundry's book includes the radical claim that removing lectins is beneficial for cancer, there are actually a growing number of preliminary studies which show that lectins may have anti-tumor properties. One study found that patients with colorectal cancer, compared to a control group, showed benefit from eating plant lectins. Researchers are still figuring out exactly how this might work on a molecular level, but in various human studies, lectins have been shown to be able to bind cancer cell membranes, potentially leading to cell death or inhibiting tumor growth. One review concluded “these inspiring findings would open a new perspective for plant lectins as potential...drugs from bench to clinic.”
This is where I've found disagreements in nutrition usually lead. For each claim, there's a counter-claim, and each side seems to be able to offer evidence to support the argument they're making. It's a game of nutrition study ping pong and it gets confusing pretty quickly for those of us trying to make food choices. Though I'm still on the side of beans and bread, it was disorienting to hear rebuttals from Gundry, and have to go back and look for either support or refutation.
Katz encourages me, as a consumer, to take a step back, breathe, and look at the overall picture, rather than fuss about the details. When making dietary choices for yourself, instead of getting lost in the debate over what lectins do alone, we should be asking: What happens overall to people who eat foods that are high in lectins?
Antigone Kouris is an associate professor at La Trobe University in Melbourne, Australia, and has been a clinical dietitian and research dietitian for more than 30 years. Her research has focused on the Mediterranean diet, and found that following a more plant-based, legume-based diet pattern tends to reduce mortality after 5 years. “Food is like an orchestra," she says. "The orchestra needs all the members to work. You take one member out of the orchestra [and] it's not the same."
Kouris has conducted meta-analyses of existing research and found that replacing several meat-based meals a week with legumes can have a positive impact on longevity, glycemic control, diabetes, cardiovascular disease, and weight management.
In a study led by one of Kouris’s PhD students, Irene Blackberry, they found that legumes were the most important dietary predictor of survival in older people in four different countries: Japan, Sweden, Greece, and Australia. They looked at 785 people who were 70 years and older, and then followed them up to seven years. “Irene analyzed the information on every single different food that she collected,” Kouris says. “And then when she compared statistics, the most important food group that came out as being significant for mortality, or reducing mortality, were legumes.”
It's easy to find many more, large-scale studies online which show that consuming nuts and legumes reduce heart disease, stroke, and diabetes, or that eating whole grains is associated with lowering the risk of chronic diseases and with lower BMIs and weight management. Kouris says studies usually show that vegetarians have lower rates of chronic illness, which wouldn't make sense if lectins were bad for you. (Also, Katz and Kouris both assure me that you don’t need a pressure cooker to eat beans. The people in the Blue Zones didn’t need pressure cookers, and neither did the people in Greece or Japan that Kouris and her colleagues studied.)
Bourns says that at the recent Whole Grain Summit in Vienna (yes, that’s a thing) more than 200 scientists from 36 countries worked on a two-year global plan with the goal of increasing whole grain consumption. Why? Data from the Institute for Health Metrics and Evaluation, a research institute at University of Washington in Seattle, found that replacing refined grains with whole grains could reduce the burden of chronic disease more than any other change, even reducing salt, eliminating trans fats, or cutting sugar-laden drinks. Bourns tells me that very much like with legumes, studies have shown risk reduction for diabetes, cardiovascular disease, colonic diseases, cancer, and more in groups who eat whole grains. "This would not happen if the grains would make you sick overall," he says.
So how is Gundry’s book filled with scientific citations? My friend, and many others, read it and saw its long bibliography and thought it was backed by evidence. But a closer look at the citations reveals some issues. T. Colin Campbell, an emeritus professor of nutritional biochemistry at Cornell University documented how many of Gundry’s claims either stem from poster presentations (so, not peer-reviewed data) or refer to citations that don’t exactly back what he’s saying.
“Dr. Gundry cherry-picked the literature, and the literature that he cherry-picked, in this case, is substantially irrelevant,” Katz says.
Bourns worries that people who get caught up in this diet will lose a main source of fiber as a result, but Katz isn't as concerned by any singular health detriment from the lectin-free fad. Ultimately, Katz says, a diet is only as harmful as your ability to adhere to it. And Gundry’s diet is pretty hard to keep to. Even the most stringent meat eater would likely have a hard time avoiding all the plant foods listed in The Plant Paradox. "How much will this hurt you in six weeks?" Katz says. "I don't know. A little. You're not getting much fiber, so you'll be constipated, then you'll go back to wherever you were before, which, by the way, if you're American, is probably constipated to begin with since Americans get about a third of the recommended fiber.”
The real damage, Katz thinks, is that we continue to show that we’re gullible and susceptible to whatever the next fad diet is. “You've been talked into abandoning everything you ever thought was true about nutrition," he says. "What happens after that?” Until we can start approaching the way we eat with some common sense and moderation, he tells me, the ill effects of our food choices will continue to plague us.
“The United States version of the global burden of disease report was published in JAMA just two months ago, and that was the conclusion. Diet," Katz tells me. "It's always been in the top three since we started tracking this past quarter century, but now it's number one. Bad diet. The leading cause of years lost from life, life lost from years, and yet grown-ups won't grow up about it. We won't take it seriously.”
Food is more than just sustenance, it's powerful psychological tool. It gives you back the feeling of control over your body, and gives you the power of reclaiming your health. After more inquiry, my friend told me he was convinced to go lectin-free after receiving not-so-great news about his health, and an ominous allusion to what he called, "the big C," or cancer. When I discovered that, and then read the introduction to The Plant Paradox, my friend's willingness to sign on made a lot more sense.
The book says: "First, repeat after me: 'I am not to blame.' That’s right: your health problems are not your fault... The secrets I’ll share with you will reveal what is keeping you sick, tired, depleted of energy, overweight (or underweight), fuzzy headed, or in pain. And once you discover and remove the roadblocks standing in the way of vibrant health and a slim body, your life will change... While health 'experts' have pointed to our laziness, our addiction to fast food, our consumption of beverages full of high-fructose corn syrup, and the host of toxins in the environment as causes for our current ailments (among many others), sadly they are wrong."
This argument panders to our most basic desires. That our sick bodies are not our fault—or the fault of our food system or government—and that there is an easy, quick solution to our problems. The idea that a single food type is causing an overall health issue is appealing. If I just cut out "X", I’ll stop feeling so tired all the time, or it will finally help me to lose weight, or make my whole digestive system better.
The truth is that, as much as the studies I've cited show the benefit of eating beans, even they are not a magical pill. Bourns told me that lectins could bind to cancer cells, does that mean we should rebound and do the extreme opposite: all lectins all the time? No. Many factors go into a healthy and balanced life and body, including a wide variety and combination of foods, an active lifestyle, a mental life not weighed down by stress, all mixed in with the genes you were born with. To isolate any of these one things as the solution to health is just as bad as to isolate lectins as the sole cause of bad health.
We live an immobile lifestyle fueled by foods wrapped in plastic, rather than an active one powered by whole foods. At my job, it was recently announced that management had partnered with a popular local salad restaurant, so that we could get our salads sent to the office, with free delivery. While the gesture is a good one—and encourages salad eating—I found it depressing. We already exist in a work culture that discourages movement. Most people don’t take a lunch break, or even time to walk around the block; instead eating at their desks. The salad place is a ten-minute walk away, according to Google maps. But we will have our salad delivered, rather than taking the opportunity to walk half a mile in the sun. We want to eat a $15 salad for lunch to be "healthy," but what’s the net benefit if we don’t prioritize the other stuff too?
The true paradox about nutrition and health is that it’s both extremely simple and difficult at the same time. We know what’s good for us. We know that we should move our bodies and eat healthily. And yet we’ve constructed a world filled with stress and mechanical conveniences, and created foods that feel good to eat even though they’re bad for our bodies, and then we don’t eat them in moderation; we let them dominate our diets.
Katz thinks that it could be simpler. He recently founded the True Health Initiative, a council where leading figures from every dietary preference can come together and try to agree on some fundamentals. There are overarching truths to be had, he says, probably not too dissimilar from Michael Pollan’s famous philosophy: Eat food, not too much, mostly plants. I worry that because this advice doesn't promise to cure all ills, or promise to be easy, that it will have a hard time catching on.
From demanding food to carry such a heavy burden—to cure us, essentially—of the woes of modern life, we lose something precious as well. Real, whole food is important for our connections to culture and to emotionally and socially tie us to each other. Creating fear, restriction, rules, and magical thinking around food strips it of those elements.
“What we really want is to be able to love food that loves us back,” Katz says. “I think these quirky diets almost cause people to forget that, yes, food should be a source of health and weight control; it should be a source of pleasure, too, and you don't have to pick. Choose a sensible dietary pattern. Then you can actually eat a variety of foods you enjoy.”
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