What Exactly Are Lectins? The Best and Worst Lectin Sources

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February 8th, 2023

By Dr. Edward F. Group

Guest Writer for Wake Up World

You may have heard of gluten — and the dietary concerns it causes — but have you heard of lectin? Known as an “antinutrient,” lectin is a type of plant-based protein commonly found in seeds, grains, legumes, and tubers, like potatoes. As an antinutrient, lectins may prevent your body from absorbing essential vitamins and minerals — but that’s not all.

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Research indicates that lectins may put certain people at risk for systemic inflammation, digestion concerns, increased fat storage, and even autoimmune conditions, such as celiac disease and Crohn’s disease.[1, 2, 3] They can trigger higher histamine levels, which can cause a reaction in some people.

Although extensive research exists on the harmful effects of lectins, the jury is still out. Some experts say concerns about lectins are overstated since we cook many lectin-containing foods.

So what’s the verdict? Are lectins bad for you? Let’s dig into the research.

What Are Lectins?

Lectins are a broad class of protein found abundantly in plants. Lectins protect plants against microorganisms, insect pests, and animals that may eat them.[1]

To the scientifically minded, lectins are “glycoproteins that bind carbohydrates and agglutinate cells.”[4] Agglutinate means to clump; known as “sticky proteins,” lectins cause cells — including red blood cells, gut mucosal cells, and even probiotic bacteria — to clump together.[5]

Rather than being digested and broken down, lectins survive the mammalian digestive system; this allows things like seeds to pass through a mammal’s gut and still germinate. Lectins are particularly high in seeds.

However, to people, this may lead to gastrointestinal distress.[1] Because we do not digest lectins, our bodies see them as foreign objects and produce antibodies to “attack” them; in other words, they trigger an immune system reaction.[6, 7]

Are Lectins Bad for You?

Research strongly suggests that consuming high amounts of lectins can cause health concerns in some people who have a genetic sensitivity to them.[8] The concern is that most people do not know their genetic makeup — only that they experience health issues. When you have gut issues or low energy or brain fog, but most doctors don’t think to test for histamine intolerance.

After you eat lectins, they bind to cell membranes, particularly those lining the digestive tract — called gut epithelial or gut mucosal cells.[1, 3] This binding can cause gut cells to die or lose function; lectins can also clump gut microbes together, disrupting an otherwise healthy gut biota.[1]

Lectins also affect lipid, carbohydrate, and protein metabolism.[1] In small amounts, lectins may even have health benefits, but in higher amounts they may cause health concerns.[5]

Not all lectins are bad, but most people in the Western world eat too many of the problematic high-lectin foods — particularly grains and beans and even tomatoes.[1]

If you regularly experience inflammation, disease, or gastrointestinal distress, try eliminating lectins and see if it helps. If you already have damaged gut mucosa, cutting out lectins will not make anything heal overnight, and you may not see immediate results from eliminating them. Your body may require time to heal.

5 Reasons to Avoid Lectins

If you are considering avoiding or minimizing lectins in your diet, here are the top science-based reasons.

1. Lectins Are Antinutrients

Scientists refer to lectins as “antinutrients” — compounds that interfere with the body’s ability to digest and use other nutrients. Lectins, in particular, block absorption of calcium, iron, phosphorus, and zinc — essential minerals.[9]

If you eat lectin-rich beans along with other foods containing zinc or iron — or with your daily multivitamin — your gut may not absorb the minerals properly. Knowing this, you can consume these minerals or your multivitamin during a meal that does not contain lectins.

2. Lectins May Cause Inflammation

Studies show that lectins cause redness and swelling — in other words inflammation — in the body by activating pro-inflammatory pathways. This affects your immune system functioning.[3, 4] Lectins cause the body to create antibodies as if lectin was a foreign invader, like a virus.[6]

Inflammation caused by consuming too many lectins may lead to autoimmune diseases such as rheumatoid arthritis and celiac disease — particularly in individuals with dysfunctional digestive enzymes.[8] Long-term body inflammation increases your risk of heart disease and cancer.

Lectins also may stimulate a series of biochemical reactions that affect the pancreas and islet cells, which make the body vulnerable to an autoimmune attack, as well as diabetes.[8] Gluten actually contains lectin, so people with gluten-sensitivity are especially advised to eliminate or minimize lectin intake.[8]

3. Lectins May Permeate the Gut Barrier

When you consume lectins, they can damage the intestinal wall or epithelium.[6, 10, 11] While a healthy gut can repair itself from small amounts of damage, consuming high quantities of lectins could eventually lead to a leaky gut.[10, 11]

A healthy gut keeps partially digested food and microbiota in, only permitting nutrients to flow out as they should.

A leaky gut, on the other hand, has weakened “tight junctions” that allow toxins, food molecules, pathogens — and lectins — to pass through.[8, 11]

Over time, a leaky gut can lead to chronic inflammatory conditions such as inflammatory bowel disease, Crohn’s disease, autoimmunity, neurological disorders, and allergies.[10]

4. Raw Lectins May Be Toxic

Consuming undercooked or raw legumes may be toxic.[4, 6] When a hospital served red kidney beans for a “healthy eating day,” several people experienced severe vomiting and diarrhea. No pathogens were found in the beans, yet they contained particularly high levels of phytohaemagglutinin — a lectin that has caused other cases of “food poisoning.”[8]

Side note: Because of the high toxicity of raw beans, never let young children play with them since they may swallow them.

Cooking beans in a pressure cooker at a high temperature, or boiling them on the stove for at least 10 minutes, should denature lectins, making beans safer to eat.

Keep in mind that according to research, cooking them in a slow cooker or Crock Pot may not heat legumes to a high enough temperature to denature, or break down, the lectins.[12, 13]

5. Lectins May Cause Digestive Distress

Lectins clump (or agglutinate) cells, including helpful microbes as well as gut mucosal cells; this agglutination can cause gastrointestinal distress.[1, 5] As with gluten, not everyone responds the same way to lectin, and not everyone will experience side effects from eating the same foods.[1]

Lectins may cause immediate symptoms in some people — typically GI symptoms like diarrhea, bloating, gas, or constipation. But in other people, lectins may silently damage your gut and body systems without you realizing it.[8]

Foods High in Lectins

About 30 percent of the foods we eat contain lectins.[6] Although some high-lectin foods also contain antioxidants, nutrients, and fiber, and may even provide benefits in small amounts,[5] some nutritional experts advise you to avoid high-lectin foods or to limit your overall intake.

According to Cornell University, the amount of lectins in plant foods — and their “agglutinating” properties — can vary from day to day and from store to store, so you may never know when you’ll end up with a batch of beans with a too-high amount.[5]

If you have digestion concerns, like constipation or diarrhea, you might consider cutting out lectins for a while and see if your digestion improves.

The following foods are sources that are particularly high in lectins:[13]

  • Red kidney beans
  • Navy beans
  • Chickpeas (garbanzo beans)
  • Soybeans and soy products
  • Black beans
  • Lima beans
  • Lentils
  • Black-eyed peas (cowpeas)
  • Peanuts
  • Wheat and other grains
  • White potatoes
  • Nuts
  • Nightshade vegetables including tomatoes, eggplant, peppers
  • Corn
  • Dairy

Popular Low-Lectin Foods

If you worry about your consumption of lectins, there are plenty of healthy foods low in lectins to choose from. None of these foods is better than the others. Aim to eat a variety of these foods. Eating a diverse mix of whole, natural foods helps you consume a variety of nutrients for optimal health.

  • Celery
  • Garlic
  • Onion
  • Broccoli
  • Cauliflower
  • Brussels sprouts
  • Dark leafy greens
  • Asparagus
  • Mushrooms
  • Avocado
  • Artichokes
  • Beets
  • Kimchee
  • Sweet potatoes
  • Olives
  • Olive oil
  • Citrus fruit

Should You Try a Lectin-Free Diet?

Choosing to avoid food that’s high in lectin is a personal choice. Dr. Steven Gundry popularized the lectin-free diet with his book, “The Plant Paradox.” If consuming foods such as beans and grains causes you digestive concerns, such as bloating or stomach discomfort, eliminating them from your diet may alleviate these symptoms.

A lectin-free diet in and of itself likely will not cause weight loss, but eliminating the processed grain products that plague the Standard American Diet (nicknamed “SAD”) — and happen to have high lectin content — could help you shed pounds.

If you cut out foods with lectins, you may notice a quick change, or you may see no changes in your body. However, keep in mind that some benefits may work quietly inside your cells and tissues.

If you want to know whether you have a genetic susceptibility to lectins, you can also order a DNA kit online that will sequence your genes and reveal certain health conditions.[14]

If you feel you can’t live without high-lectin foods like beans and seeds, yet experience some digestion distress, you can try taking something known to reduce systemic redness and swelling like turmeric, and take a high-quality probiotic. Global Healing’s Global Healing’s Ultimate Probiotic contains 25 unique probiotic strains plus prebiotics and phages for superior digestive support.

Other Natural Ways to Reduce Lectin Intake

If you choose to cut back on your intake of lectins, eliminating high-lectin foods isn’t your only option. Below are the best ways to reduce lectins in these otherwise healthy foods so you can get the benefit of their nutrients — without the antinutrients.

Cooking

Properly cooking foods reduces lectin levels, but they are surprisingly resistant to temperature. One study found moist heat more effectively denatures lectin protein than dry heat, though commercial roasting of nuts was enough to break down the lectins 100 percent.[16]

Research has found that cooking decreases antinutritional compounds in chickpeas (although they did not look specifically at lectins).[15]

Some studies have suggested that conventional home cooking may not break down lectins since they are very heat-stable; moist or dry heating at just 70 degrees C (158 degrees F) did nothing to the lectins in one study.[12] When cooking beans at over 100 degrees C (212 F), it only took 10 minutes to break down lectins, at 95 degrees C (203 F) it took one hour.[12]

In other words, you should cook lectin-containing foods at a high enough temperature to eliminate them.

Fermenting

Fermentation also reduces the lectin content. One study found that fermenting lectins for 72 to 96 hours resulted in almost complete elimination of lectins.[17] Fermented foods include kimchee (fermented cabbage), sauerkraut, and natto. Another study found fermenting foods made from beans reduced their lectin content up to 95 percent.[17]

Soaking

Another way to reduce lectins in foods is by soaking them, particularly legumes and grains.[18, 19] Soaking deactivates about 50 percent of the lectins in beans.[19]

Adding sodium bicarbonate (baking soda) to the water and soaking for 16 hours reduced levels of antinutrients in cowpeas in a study.[20] If you cook beans, always soak them overnight, dump the soaking water, and then boil them in fresh water to reduce the lectin content.

Sprouting

You can go a step further by sprouting beans and grains, which may reduce the lectins in chickpeas and other legumes substantially.[15] Germinating beans for 42 hours at 77 degrees F decreased lectins by almost 59 percent in one study.[21]

Points to Remember

You may experience nausea, diarrhea, or other digestive symptoms from consuming lectin-containing foods, without realizing the culprit. Lectins are carbohydrate-binding proteins found in many plant foods such as beans, legumes, grains, dairy, and some vegetables. The more lectins in a particular food, the fewer sugars and starches are absorbed by your body.[22]

Lectins are called “antinutrients” because consuming high quantities of lectin foods can prevent your body from absorbing other nutrients, particularly calcium, iron, phosphorus, and zinc.

Several studies on both humans and animals have found that lectins cause inflammation and digestive concerns and may even contribute to autoimmune disease.

If you wish to reduce your consumption of lectins, cooking, soaking, sprouting, and fermenting beans, legumes, and grains will lower the level of lectins in those foods.

References:

  1. Vasconcelos IM, Oliveira JT. Antinutritional properties of plant lectins. Toxicon. 2004 Sep 15;44(4):385-403.
  2. Astley A, Finglas P. Nutrition and health. Reference Module in Food Science. Elsevier Publishing. 7 May 2016.
  3. Gong T, et al. Plant lectins activate the NLRP3 inflammasome to promote inflammatory disorders. J Immunol. 2017 Mar 1;198(5):2082-2092.
  4. Peumans WJ, Van Damme JM. Lectins as plant defense proteins. Plant Physiol 1995;109:347-352.
  5. Plant Lectins. Cornell University, College of Agriculture and Life Sciences. Updated 4 Sep 2018. Accessed 24 Oct 2018.
  6. Vojdani A. Lectins, agglutinins, and their roles in autoimmune reactivities. Altern Ther Health Med. 2015;21 Suppl 1:46-51.
  7. Tchernychev B, Wilchek M. Natural human antibodies to dietary lectins. FEBS Lett. 1996 Nov 18;397(2-3):139-42.
  8. Freed D. Do dietary lectins cause disease? BMJ. 1999 Apr 17;318(7190):1023-1024.
  9. Are anti-nutrients harmful? The Nutrition Source, T.H. Chan School of Public Health, Harvard University. Accessed 22 Mar 2019.
  10. De Punder K, Pruimboom L. The dietary intake of wheat and other cereal grains and their role in inflammation. Nutrients. 2013 Mar;5(3):771-787.
  11. Lee SH. Intestinal permeability regulation by tight junction: Implication on inflammatory bowel eiseases. Intest Res. 2015;13(1):11-18.
  12. Pusztai A, Grant G. Assessment of lectin inactivation by heat and digestion. Methods Mol Med. 1998;9:505-514.
  13. Dolan LC, et al. Naturally occurring food toxins. Toxins (Basel). 2010 Sep;2(9):2289-2332.
  14. What is direct-to-consumer genetic testing? US National Library of Medicine. Updated May 2018. Accessed 22 Mar 2019.
  15. El-Adawy TA. Nutritional composition and antinutritional factors of chickpeas (Cicer arietinum L.) undergoing different cooking methods and germination. Plant Foods Hum Nut. 2002 Winter;57(1):83-97.
  16. Ahmed EM. Lectin quantitation in peanut and soybean seeds. Peanut Science. 1986;13:7-10.
  17. Cuadrado C, et al. Effect of natural fermentation on the lectin of lentils measured by immunological methods. Food Agric Immunol, 2002;14(1):41-49.
  18. Reddy NR, Pierson MD. Reduction in antinutritional and toxic components in plant foods by fermentation. Food Res Int. 1994; 27(3):281-290.
  19. Siddiq M, et al. Processing of sugar?coated red kidney beans (Phaseolus vulgaris): fate of oligosaccharides and phytohemagglutinin (PHA), and evaluation of sensory quality. J Food Sci. 2006 Nov/Dec;71(9):C521-C526.
  20. Ibrahim SS, et al. Effect of soaking, germination, cooking and fermentation on antinutritional factors in cowpeas. Nahrung. 2002 Apr;46(2):92-95.
  21. Paucar-Menacho LM, et al. Optimisation of germination time and temperature on the concentration of bioactive compounds in Brazilian soybean cultivar BRS 133 using response surface methodology. Food Chem. 2010 Mar;119(2):636-642.
  22. Rea RL. Lectins in foods and their relation to starch digestibility. Nutr Res. 1985;5(9):919-929.

Originally published at Global Healing Center and reproduced here with permission.

About the author:

Dr. Edward F. Group III (DC, ND, DACBN, DCBCN, DABFM) founded Global Healing Center in 1998 with the goal of providing the highest quality natural health information and products. He is world-renowned for his research on the root cause of disease. Under his leadership, Global Healing Center earned recognition as one of the largest natural and organic health resources in the world. Dr. Group is a veteran of the United States Army and has attended both Harvard and MIT business schools. He is a best-selling author and a frequent guest on radio and television programs, documentary films, and in major publications.

Dr. Group centers his philosophy around the understanding that the root cause of disease stems from the accumulation of toxins in the body and is exacerbated by daily exposure to a toxic living environment. He believes it is his personal mission to teach and promote philosophies that produce good health, a clean environment, and positive thinking. This, he believes, can restore happiness and love to the world.

For more, please visit Global Healing Center.

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