What Are Lectins?

Lectins are a type of protein found in plant-based foods that can bind carbohydrates. They occur naturally in cereals, beans, lentils, vegetables, some animal foods, and fish. Certain lectins, such as ricin, which comes from castor beans, are highly toxic. If you watched Breaking Bad, you may remember ricin!

While lectins may sound evil, they do serve a purpose. Lectins are present in food for plant growth and immunity. They protect plants from predators and disease activity, including bacteria and viruses. Lectins help bind carbohydrates for storage and transport. ^[2] Chettri, D., Boro, M., Sarkar, L., & Verma, A. K. Lectins: Biological significance to biotechnological application. Carbohydrate Research, 506, 108367. https://doi.org/10.1016/j.carres.2021.108367 2021

Amy Woodman, RD, founder of Farmington Valley Nutrition and Wellness notes, “Lectins, often referred to as anti-nutrients, are thought to be proinflammatory phytochemicals that may contribute to this process, although the research is not definitive. Much of the research implicating lectins comes from animal or in vitro studies, which do not accurately reflect the exposure to lectins from eating properly prepared and cooked foods.”

Certain lectins, such as phytohaemagglutinin (found in high concentrations in the red kidney bean), can impact the gut by decreasing acid secretion and altering the absorptive capacity of the small intestine. ^[3] Panacer K, Whorwell PJ. Dietary Lectin exclusion: The next big food trend? World J Gastroenterol. 2019 Jun 28;25(24):2973-2976. doi: 10.3748/wjg.v25.i24.2973. PMID: 31293334; PMCID: PMC6603809.

Lectins may also have an indirect effect on the pancreas. Some evidence suggests that certain lectins affect the gut microbiota and have systemic effects, including inflammation and altered immune function. ^[3] Panacer K, Whorwell PJ. Dietary Lectin exclusion: The next big food trend? World J Gastroenterol. 2019 Jun 28;25(24):2973-2976. doi: 10.3748/wjg.v25.i24.2973. PMID: 31293334; PMCID: PMC6603809.

In reality, not all lectins are harmful, and certain techniques may reduce your exposure to them. Sensitivity to lectins varies in individuals and may depend on a person’s medical history.

Foods High in Lectins (Lectins Foods List)

Kidney beans (especially raw or undercooked)

As mentioned above, kidney beans contain phytohaemagglutinin. Lectins in red kidney beans may not be harmful when they are cooked well and not eaten raw. ^[2] Chettri, D., Boro, M., Sarkar, L., & Verma, A. K. Lectins: Biological significance to biotechnological application. Carbohydrate Research, 506, 108367. https://doi.org/10.1016/j.carres.2021.108367 2021

Soybeans

Soybeans contain lectins, but are a good source of complete protein, fiber, and isoflavones, which have disease-fighting properties. ^[4] Messina M, Duncan A, Messina V, Lynch H, Kiel J, Erdman JW Jr. The health effects of soy: A reference guide for health professionals. Front Nutr. 2022 Aug 11;9:970364. doi: 10.3389/fnut.2022.970364. PMID: 36034914; PMCID: PMC9410752. The most commonly eaten soy product is tofu. The way tofu is processed keeps lectin levels low. ^[5] Stanojević SP, Kostić AŽ, Milinčić DD, Pešić MB. Assessment of soy genotype and processing method on trypsin inhibitors, urease and lectins content of tofu. Nat Prod Res. 2024 Dec;38(24):4317-4324. doi: 10.1080/14786419.2023.2280858. Epub 2023 Nov 17. PMID: 37976506.

Peanuts

Peanuts are another source of lectins. Roasting peanuts helps to reduce the number of lectins present in peanuts or peanut butter.

Lentils

Like other legumes, lentils do contain lectin. However, lentils are a healthy addition as part of the Mediterranean diet. According to a 2022 study, they help to reduce the risk of gastric cancer. ^[6] Tayyem R, Al-Awwad N, Allehdan S, Ajeen R, Al-Jaberi T, Rayyan Y, Bawadi H, Hushki A. Mediterranean Dietary Pattern is Associated with Lower Odds of Gastric Cancer: A Case-Control Study. Cancer Manag Res. 2022 Jun 17;14:2017-2029. doi: 10.2147/CMAR.S360468. PMID: 35747711; PMCID: PMC9211070.

Chickpeas

As mentioned above, chickpeas are another source of lectins. Similar to other beans, chickpeas should not be consumed raw or undercooked. Cooking them reduces their lectin content.

Tomatoes

Tomatoes are part of the nightshade family and contain small amounts of lectins. Tomatoes may be eaten raw or cooked without issues.

Potatoes

Potatoes are also a nightshade vegetable. Potatoes should be eaten cooked, versus raw. Peeling potatoes before cooking them will reduce their lectin content. Sweet potatoes are lower in lectins. ^[7] Do Potatoes Have Lectins? - Lectin Foods Base

Eggplant

Eggplant isn’t a commonly consumed vegetable, but it is part of a Mediterranean diet. Similar to other nightshade vegetables, it’s a source of lectins. It is rarely eaten raw, and cooking eggplant will reduce the lectins in this vegetable.

Bell peppers

Bell peppers may also contain lectins and are considered a nightshade vegetable. Peeling and removing the seeds from bell peppers will reduce their lectin content. ^[8] How to Remove Lectins from Bell Peppers: A Comprehensive Guide

Wheat and other whole grains

Wheat and other whole grains like farro and bulgur provide gluten, as well as lectins. Both of these proteins may be avoided in individuals with IBS who are following a low-FODMAPs diet. ^[2] Chettri, D., Boro, M., Sarkar, L., & Verma, A. K. Lectins: Biological significance to biotechnological application. Carbohydrate Research, 506, 108367. https://doi.org/10.1016/j.carres.2021.108367 2021

Corn

What’s summer without corn on the cob? While some consider corn a “vegetable”, it’s a grain. Corn, like other grains, contains lectins. Boiling or simmering corn will reduce its lectin content.

Quinoa

Quinoa is botanically a seed, though most in the nutrition world consider it a grain. Quinoa is gluten-free, and a good source of protein and fiber. While it does contain lectins, they are inactivated when quinoa is cooked. ^[9] Adamcová A, Laursen KH, Ballin NZ. Lectin Activity in Commonly Consumed Plant-Based Foods: Calling for Method Harmonization and Risk Assessment. Foods. 2021 Nov 13;10(11):2796. doi: 10.3390/foods10112796. PMID: 34829077; PMCID: PMC8618113.

Peas

Peas are part of the legume family and also contain lectins, too. By cooking or heating peas, their lectins are inactivated.

Zucchini

While zucchini isn’t a nutritional powerhouse like kale, it’s gained popularity as a low-carb option for noodles. Zucchini skin has lectins, but the flesh does not. Peeling zucchini will lower its lectin content.

Pumpkin seeds

Pumpkin seeds are a source of lectins, too. You can reduce the lectins by boiling, roasting, fermenting, or toasting pumpkin seeds, according to Chef’s Resource. ^[10] Melissa T. Jackson How to remove lectins from pumpkin seeds? 2024

Why Do Some People Avoid Lectins?

Leaky gut syndrome is a condition in which the gut lining is compromised (broken down) due to stress, poor diet, alcohol, medications, and other environmental factors. This breakdown can allow harmful substances and bacteria to “leak” through the bloodstream, leading to autoimmune diseases such as MS, lupus, and Celiac disease.

Toxins in the blood may also impact gastrointestinal conditions such as IBS and Crohn’s disease by increasing inflammation in the gut. Individuals with these conditions may wish to avoid lectins in their diets to prevent further damage to their intestinal lining. ^[11] Aleman RS, Moncada M, Aryana KJ. Leaky Gut and the Ingredients That Help Treat It: A Review. Molecules. 2023 Jan 7;28(2):619. doi: 10.3390/molecules28020619. PMID: 36677677; PMCID: PMC9862683.

According to Kellie Blake, RDN, LD, IFNCP, Owner, NutriSense Nutrition Consulting, “Leaky gut allows large undigested food particles, toxins, and microbes to flow across the barrier into the systemic circulation (bloodstream) where they wouldn’t normally go. As a result, the immune system mounts an attack leading to numerous symptoms, both inside and outside the gastrointestinal tract.“

Leaky gut is associated with many chronic, inflammatory conditions including obesity, type 2 diabetes, autoimmunity, and mental health disorders

While some lectins, such as phytohemagglutinin (found in uncooked red and white kidney beans) are associated with inflammation and an autoimmune response, more research is needed on how lectins affect the gastrointestinal system. ^[12] Konozy, E. H., & Osman, M. E. M. (2024). From inflammation to immune regulation: The dual nature of dietary lectins in health and disease. Heliyon, 10(20), e39471. https://doi.org/10.1016/j.heliyon.2024.e39471

Deepa Deshmukh, MPH, RDN, CDCES, BC-ADM of www.nutritionistdeepa.com notes,” IBS and Crohn’s disease involve chronic inflammation and often an autoimmune component. Reducing gut irritants allows the intestinal lining to heal. Although avoiding lectins sounds prudent, in practice, almost no one eats raw legumes. Routine cooking methods—soaking and boiling—effectively deactivate lectin.”

While a lectin-free diet sounds prudent, it’s nearly impossible to avoid all lectins as they’re present in roughly 30% of our food. ^[13] Vojdani A. Lectins, agglutinins, and their roles in autoimmune reactivities. Altern Ther Health Med. 2015;21 Suppl 1:46-51. PMID: 25599185. Foods containing lectins are typically nutritious foods including legumes, whole grains, and vegetables. Avoiding them completely would drastically reduce the fiber content of your diet, which is not advised.

Are Lectins Always Harmful? (The Other Side of the Story)

Foods containing lectins aren’t evil. In fact, many lectin-rich foods are also high in fiber, antioxidants, phytochemicals, and other nutrients. Beans, for example, provide 6 grams of fiber per half cup serving, which is 24% of the Daily Value for dietary fiber. Peppers, potatoes, and tomatoes are high in vitamin C and other nutrients.

Several lectin-containing foods are part of the Mediterranean diet, which has been shown to reduce the risk of diabetes, cognitive decline, and obesity according to a 2022 study published in the Journal of Internal Medicine. ^[15] Guasch-Ferré M, Willett WC. The Mediterranean diet and health: a comprehensive overview. J Intern Med. 2021 Sep;290(3):549-566. doi: 10.1111/joim.13333. Epub 2021 Aug 23. PMID: 34423871.

In addition, beans and whole grains, which contain lectins, provide dietary fiber. When fiber is broken down, it produces short-chain fatty acids, which are linked with a lower incidence of colon and colorectal cancer. ^[16] Zeng H, Hamlin SK, Safratowich BD, Cheng WH, Johnson LK. Superior inhibitory efficacy of butyrate over propionate and acetate against human colon cancer cell proliferation via cell cycle arrest and apoptosis: linking dietary fiber to cancer prevention. Nutr Res. 2020 Nov;83:63-72. doi: 10.1016/j.nutres.2020.08.009. Epub 2020 Aug 22. PMID: 33017771.

Tips to Reduce Lectins Without Cutting Out Nutritious Foods

Soak legumes overnight

Soaking legumes overnight will help to reduce their lectin content. Legumes should never be eaten raw, and from a taste and texture standpoint, wouldn’t be very tasty this way.

Boil thoroughly (especially kidney beans)

Boiling foods high in lectins, like beans or corn, will reduce their lectin content. Kidney beans are especially high in lectin concentration and should never be consumed raw.

Use pressure cooking

Pressure cooking is another method to reduce lectins in foods. An Instant Pot or other pressure-cooking device is a great way to cook foods quickly.

Fermentation

Fermenting foods is not only a way to decrease lectins in foods, it’s also a way to alter your foods’ probiotic content. Fermented soybeans or eggplant are great for your gut health! ^[14] Belobrajdic DP, James-Martin G, Jones D, Tran CD. Soy and Gastrointestinal Health: A Review. Nutrients. 2023 Apr 19;15(8):1959. doi: 10.3390/nu15081959. PMID: 37111176; PMCID: PMC10144768.

Peeling and deseeding vegetables like tomatoes and peppers

Lectins are often present in the skins of fruits and vegetables. Peeling potatoes, tomatoes, and zucchini will help reduce their lectin content.

Should You Try a Lectin-Free Diet? (Pros & Cons)

According to Amy Woodman, RD, “It is unclear whether eliminating lectins would help with IBD or autoimmune conditions. In general, lectins are found in high-fiber foods, which offer numerous health benefits.”

A lectin-free diet may be helpful for individuals with autoimmune conditions, but should only be considered under a physician’s guidance.

Woodman notes, “while patients may want to avoid high-fiber foods during IBD or IBS flares, research indicates that avoiding fiber altogether may not be beneficial.” ^[17] Brotherton CS, Martin CA, Long MD, Kappelman MD, Sandler RS. Avoidance of Fiber Is Associated With Greater Risk of Crohn's Disease Flare in a 6-Month Period. Clin Gastroenterol Hepatol. 2016 Aug;14(8):1130-6. doi: 10.1016/j.cgh.2015.12.029. Epub 2015 Dec 31. PMID: 26748217; PMCID: PMC4930425.

Not recommended for the general public without a medical need

The general public without medical need should not be recommended to follow a lectin-free diet. There is no benefit in doing so, as most lectins are destroyed through cooking or food preparation, thereby reducing their content.

According to Woodman, “Steering people away from these foods due to their lectin content, especially when most people are not consuming enough fruits, vegetables, and fiber, may negatively impact overall health. Portraying otherwise healthy foods as unhealthy solely because they contain lectins can be misleading, as lectins are easily removed or deactivated through cooking.” ^[18] Henry J Thompson Improving human dietary choices through understanding of the tolerance and toxicity of pulse crop constituents, Current Opinion in Food Science, Volume 30, 2019, Pages 93-97, ISSN 2214-7993, https://doi.org/10.1016/j.cofs.2019.01.001.

Risk of missing out on fiber, protein, and key nutrients if too restrictive

Avoiding foods rich in lectins would be very restrictive. Fiber and other important nutrients may be missing from your diet by taking these foods out of your diet.

Woodman notes, “Avoiding lectins is controversial because lectins can be found in healthy foods like beans, legumes, whole grains, fruits, and vegetables, which are beneficial to health.

Conclusion

While lectins have been demonized in the media, a lectin-free diet is not advised for most people. Preparing these foods properly will reduce your risk of lectin exposure. Peeling certain vegetables and cooking beans and grains destroys lectins in food, making them perfectly safe to eat.

For individuals with certain autoimmune or gastrointestinal disorders, limiting lectins may be beneficial to reduce symptoms. But for the general population, a high-fiber diet that contains lectins is recommended.

Before eliminating healthy foods from your diet, consult with your healthcare provider or dietitian to confirm this is the best path forward. It’s also helpful to keep a symptom diary to monitor how your body reacts to foods containing lectins.

Foods to Limit if Going Lectin-Light

Raw legumes

• Legumes should always be cooked thoroughly.

Undercooked beans

• Never eat undercooked beans.

Processed snack foods containing soy or corn derivatives

• Avoid processed snacks containing corn or soy.