What Are Lectins—and Do You Need to Avoid Them?

Updated: May 25, 2021

Some health experts are urging people to avoid lectins, found in plant proteins. But aren't plant foods supposed to be healthy? And what are lectins anyway? The experts answer your questions here.

Experiments with plants in petri dish in the laboratory
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What are lectins?

They’re plant proteins, and they serve as part of a plant’s defense system. “Plants don’t want to be eaten and they don’t want their seeds eaten,” explains Steven Gundry, MD, a cardiologist and heart surgeon in Southern California and author of The Plant Paradox. “They can’t run or hide, so they rely on these sticky lectin proteins to paralyze insects.”

Scientist examining samples with plants. Taking a sample from a petri dish. Scientist holding a petri dish in the biological lab
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What’s the problem for humans?

In people, the potential damage from these plant proteins is more subtle, claims Dr. Gundry: “Lectins bind to sugars on the walls of the intestines.” (These sugars can also be found in the mouth, nose, and saliva.) “In the gut, lectins flip a switch that creates a space between intestinal cells, allowing bacteria and lipopolysaccharides (LPS) to cross the gut wall,” he explains. Once these things breach the gut wall, they can enter the bloodstream and potentially trigger bad reactions throughout the body, says Dr. Gundry. (Not sure what foods are major sources of plant proteins? Check out this list of the top sources.)

Where are lectins?

Lectins are found in beans, peas, lentils, nuts, squash, nightshade vegetables (eggplant, peppers, potatoes, and tomatoes), whole grains (especially whole wheat), dairy, and eggs, Dr. Gundry says. And that explains why the idea that lectins are dangerous doesn’t sit well with many nutritionists.

Heirloom variety tomatoes on dark rustic table text abundance ripe tomatoes

I thought vegetables and beans were healthy?

They are. Boston-based nutritionist Dana Greene, RD, speaks for the majority of nutritionists when she says it is hard enough to get most people to eat vegetables without demonizing them. “This diet is all the rage, but it seems to me to be less than ideal, healthwise.”

“The fear of lectins and fear of eating beans will hurt the health of the population,” warns Joel Fuhrman, MD, a family physician specializing in nutritional medicine in Flemington, NJ, and author of several books including Eat To Live: The Amazing Nutrient-Rich Program for Fast and Sustained Weight Loss. (The right diet for you may depend on your age: Here’s the best diet for every decade of life.)

Fresh eggplants on dark wooden background.. Vegetarian food, health or cooking concept.
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Lectins and leaky gut

So what’s the case against lectins? It starts with something called leaky gut syndrome (increased intestinal permeability): When lectins create those spaces in the intestinal wall, partially digested food, bacteria, viruses, and toxins can pass through, says Dr. Gundry. “Our gut has an extensive border to defend it, and if we have intruders trying to come across the border, our immune system sounds an alarm that we are being invaded,” Dr. Gundry says. Your body mounts an attack to repel the invaders, and this leads to inflammation. The symptoms of leaky gut syndrome may include constipation, regular diarrhea, gas, and bloating.

The bigger issue, explains Dr. Gundry, is that when your body is under constant attack—every time you eat lectin-rich foods—the inflammation becomes chronic and can lead to an autoimmune disease: Your immune system begins to attack healthy tissues. “Your defenses become confused and engage in friendly fire elsewhere in the body,” he explains. Here are the 7 silent signs of leaky gut syndrome.

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Lectins and heart disease

Lectins are a major driver of the immune system’s attack on blood vessels, Dr. Gundry says. In one of Dr. Gundry’s studies, he put 200 adults between the ages 51 and 86 with risk factors for heart disease (including blood vessel dysfunction), on a low-lectin diet of leafy greens, fish, olive oil, and grass-fed beef, and he had the heart patients take “anti-aging” supplements such as polyphenols from fish oil, grape seed extract, and vitamins. After six months, the diet-plus-supplements regimen reversed blood vessel dysfunction in more than 50 percent of the heart patients.

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Lectins and autoimmunity

In autoimmune diseases like lupus or rheumatoid arthritis (RA), the immune system misfires against the body’s healthy tissues and organs. The theory is that lectins essentially provide targets for the immune system. In another study authored by Dr. Gundry, 102 patients with autoimmune disease cut lectins from their diets; within six months, 94 percent were cured, in remission, biomarker negative, and off of all immunosuppressant medications, Dr. Gundry says.

Lectins and weight gain

Lectin disrupts leptin, the hormone that signals the brain when you’re full: The plant substance binds to leptin receptors, taking the hormone out of commission. Your brain never gets the message that your gut is full, and this leads to overeating and, of course, weight gain. Getting proper sleep to increase leptin is one of the weight loss tips doctors wish you knew.

Closeup view of a MRI head scan with brain and skull on it. Blue toned.

Lectins and brain diseases

“There is very strong evidence that Parkinson’s disease is, in part, driven by lectins climbing up the vagus nerve to the brain,” he says. Some studies support this theory, including a report in The FASEB Journal and a presentation at the American Gastrointestinal Association’s annual meeting. “Alzheimer’s disease and other forms of dementia may stem from a leaky gut, as well,” Dr. Gundry says. Here are some early Parkinson’s disease symptoms that are easy to miss.

Plant in laboratory
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Lectins and celiac disease

Many people with celiac disease can’t eat gluten because their body has an allergic reaction to the substance, leading to chronic digestive trouble. When patients eliminate gluten from their diets, some of them improve while others don’t, or not as dramatically. Dr. Gundry believes lectins may be to blame: “Most gluten-free products still have lectins,” he says. “It’s not just gluten—which is a lectin—that is the problem for these individuals,” he says. “If you take out all of the lectins, all of their symptoms will resolve.”

orange / red lentils. Legumes, pulses. Orange lentils full background, top view. Heap of red lentil (masoor dal) texture as background. Top view. some red lentils forming a background pattern

Should I be concerned about lectins?

Some people may be sensitive to lectins, and these individuals could potentially benefit from a diet that is low in lectin, Dr. Fuhrman says. “It’s a relatively low percentage of people who fall into this category and we have to identify them first,” he says. If you have chronic stomach problems or an autoimmune condition, talk to your physician about a short-term lectin elimination trial. Dr. Furhman suggests consulting with a doctor that is affiliated with the American College of Lifestyle Medicine. (Here are 8 true stories of how the elimination diet solved mysterious health issues.)

Assorted cereals and legumes. Protein products for vegans. Lentils, mung beans, quinoa, buckwheat, chia, beans, wild rice (Zizania), red rice, nuts

What about vegetarians?

Vegetarians and vegans, in particular, eat diets that are heavy in lectins, Dr. Gundry says. “I am not anti-vegetable.” There are ways to eat vegetables without lectins, he explains: “If you peel nightshade vegetables and remove the seeds, you remove the lectins.” What’s more, soaking beans overnight in a baking soda bath and pressure cooking them also reduces lectins, he says. Fermenting fruits and vegetables works too. Fermented foods have other health benefits too. (Check out how the fermented food kimchi protects the gut.)

red kidney beans

One lectin everyone should avoid

It’s a mouthful: Phytohemagglutinin—found in raw beans, and red kidney beans, in particular—binds to a carbohydrate present on human intestinal cells and can cause severe nausea and vomiting. This lectin is inactivated by cooking. “If you use dry beans, take the necessary precaution of making sure they are thoroughly cooked,” Dr. Fuhrman says. “Don’t eat undercooked beans. Raw beans can be toxic, and this is why we soak them overnight and cook them.”

orange / red lentils. Legumes, pulses. Orange lentils full background, top view. Heap of red lentil (masoor dal) texture as background. Top view. some red lentils forming a background pattern

A final word about lectin-free diets

This approach to eating will do more harm than good for the majority of people, stresses Dr. Fuhrman. “Plant lectins have powerful anti-cancer effects,” he says. “Beans are the highest in lectins,” he explains, “and an arm of the Nurse’s Health Study found that women who ate the most beans had the lowest risk for breast cancer. Tomatoes are also a major source of lectin, but they protect against prostate and breast cancer,” he says. Next, find out the 21 health secrets your gut is trying to tell you.