Lectin-Rich Vegetables: Benefits vs. Risks

I regularly encourage eating as much color and variety as seasonally possible because diversity is key to vitality. But, what about lectins? Is it necessary to avoid beans, vegetables, and other foods with lectins? The quick answer . . . it depends. 

What are Lectins? 

Lectins are proteins that bind to carbohydrates, and they are produced by almost all forms of life, including plants, animals, and humans. Human lectins have a number of different roles in the body, including regulation of our microbiome (i.e., the microbes that live on and inside of our bodies). 

Lectins have a variety of functions in plants, including protecting them from insects, bacteria, and fungi, which means they are a phytonutrient.

Lectin Foods List: Vegetables, Beans, and Legumes: 

• beans* (all, including sprouts)
• chickpeas* 
• lentils* (all)
• peas
• soy (including tofu)
• sugar snap peas
• edamame
• green beans
• tomatoes
• and more

*Lectin levels can be reduced by pressure cooking and/or soaking (we’ll talk about this more below). 

Lectins are also found in processed plant-based ingredients such as soy protein and pea protein, which you may find in a number of protein powder supplements, protein bars, and snacks. 

Lectins are typically found on the outside of the plant—for example, on a seed coat. Once ingested, they can also bind to cells in the human body, which can have both positive and negative effects. 

Lectins can cause food poisoning (in the case of raw red or white kidney beans) with severe gastrointestinal symptoms from a phytonutrient known as phytohemagglutinin. In fact, the Centers for Disease Control and Prevention (CDC) reports that about 20 percent of reported food poisoning cases are actually caused by consuming foods with lectins (from improperly prepared foods). 

One of the key points to understand is that most lectins are inactivated when cooked properly. 

Individuals most affected by lectins are people with autoimmune conditions and IBS. About 30-40 percent of people with autoimmune conditions are lectin intolerant, meaning that their immune system has made antibodies to lectins and reacts when they are consumed, potentially increasing inflammation as well as other symptoms. 

Another key point is that not everyone is sensitive to lectins. Therefore, if you are preparing legumes properly (see below) and eating a variety of lectin-containing fruits and vegetables, there may be benefits to consuming foods that contain reasonable amounts of lectins as they contain many nutrients beyond the lectins themselves. 

Pros of Consuming Foods With Lectins

• Lectins may help to improve gut health. A study published in the journal Gut Microbes found that lectins from legumes could increase the number of beneficial bacteria in the gut. Another mechanism by which lectins improve gut health is its ability to stimulate digestive function. It does this by producing cholecystokinin, which promotes bile secretion to break down nutrients so that they can be absorbed more easily. 
• Consuming foods with lectins are associated with many health benefits (consider the “Blue Zones” dietary patterns that often contain lectins). For example, people who regularly eat beans have a lower risk of high blood pressure, cardiovascular disease, and certain cancers. 
• Lectins are one group of phytonutrients, but each vegetable has hundreds to thousands of phytonutrients. One example of additional phytonutrients in a fruit that contains lectins is tomatoes. People who eat tomatoes benefit from the UV protective effects of lycopene and have a lower risk of heart attack and stroke. 

Cons of Consuming Foods With Lectins

• Lectins may cause digestive issues for certain people. Issues may include bloating, gas, diarrhea, and nausea. The reason for this is that lectins may not be completely digested (partially because they are stable in acidic environments), which allows them to get past the stomach and bind to and damage the cells lining the digestive tract. This can negatively impact the permeability of the intestinal membrane and interfere with absorption of nutrients. 
• Lectins interfere with the absorption of minerals. Lectins bind with calcium, iron, phosphorus, and zinc, decreasing their absorption in the intestinal tract. With that being said, it is important to remember that lectins only have a finite ability to bind minerals (I’ve heard it described that they “pull minerals out of the body,” which is not likely). When consuming foods that contain lectins, the lectins may bind with minerals primarily in the intestinal tract. Therefore, pairing foods with lectins with mineral rich foods may help decrease the risk of potential mineral deficiency caused by lectin binding. 
• Some lectins can be toxic in large quantities. This is especially true of lectins from raw beans, legumes, and grains. Cooking these foods can help to reduce the levels of harmful lectins.

Who May Want to Avoid Lectins? 

• Individuals with some autoimmune diseases:
• One study indicated that the symptoms of individuals with multiple sclerosis improved after going on a low-lectin diet (this, however, was not a randomized control trial, so more research must confirm this preliminary finding). 
• Not all individuals with autoimmune disease are sensitive to lectins; it is highly individualized. 
• Lectins cause agglutination of proteins, which may be most troublesome for those with arthritis-related autoimmune disease (such as rheumatoid arthritis).
• Individuals with irritable bowel syndrome (IBS) may experience increased sensitivity to lectins. 
• Individuals with small intestinal bacterial overgrowth (SIBO):
• Oftentimes, individuals with SIBO have a hard time eating high-lectin foods, but it is likely due to the high fiber content of lectin-containing foods. 
• These individuals may report negative inflammatory effects after eating lectins such as digestive discomfort, joint pain, and brain fog even when cooked properly because of the fermentation that occurs with the carbohydrates and fiber in the foods with lectins. 

Overall, the evidence on the health effects of lectins is mixed. Many lectin-containing foods have well researched health benefits while others may be harmful (specifically in the case of uncooked legumes and grains). 

Here are some tips for reducing the risk of adverse effects from foods with lectins: 

1. Soak beans and legumes overnight (at least six hours):
1.  Soaking beans and legumes overnight can help to reduce the levels of harmful lectins in these foods. After soaking, make sure to discard the water, rinse the beans or legumes, and refill with fresh water prior to cooking. 
2. Cook foods high in lectins thoroughly: 
1. Cook at temperatures of at least 212 degrees Fahrenheit for ten to thirty minutes (or until properly cooked; most legumes take much longer than this to be cooked to a desirable texture). 
2. Specifically consider using a pressure cooker to reduce lectins for beans, tomatoes, and potatoes. 
3. Eating sprouted forms of lectin foods, such as sprouted grains, may reduce lectin content by approximately 60 percent.
4. Certain foods like peanuts contain lectins that are more stable when heated and not easily destroyed so may be best avoided in large quantities if sensitive to lectins.
5. Ferment foods:
1.  Fermenting vegetables (such as soy), fruits, and even legumes allows beneficial microbes to  break down and reduce some of the lectins. 
6. Peeling and deseeding high-lectin foods:
1. Removing the skins and seeds from fruits and vegetables such as squash, cucumber, eggplant, and tomatoes can reduce the lectins. Peel the skin off your high-lectin fruits and veggies, and remove as many of the seeds as possible in addition to cooking them. 

By following these tips, you can enjoy the health benefits of including as much diversity into the diet as possible. 

Farmacy at The Chef’s Garden

Let The Chef’s Garden at Home be your Farmacy. We offer colorful seasonal vegetables harvested at the peak of ripeness delivered right to your doorstep, so skip the stress of shopping and experience the joy of opening a box filled with beautiful, vibrant vegetables. The hardest decision will be what to try first! 

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References: 

Cohen, L.J., Han, S.M., Lau, P. et al. Unraveling function and diversity of bacterial lectins in the human microbiome. Nat Commun 13, 3101 (2022). https://doi.org/10.1038/s41467-022-29949-3

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.

Lectins: The Nutrition Source. Harvard University. https://www.hsph.harvard.edu/nutritionsource/anti-nutrients/lectins/#:~:text=It%20is%20possible%20that%20one,lectins%20and%20other%20anti%2Dnutrients.

Wu, L., Bao, Jk. Anti-tumor and anti-viral activities of Galanthus nivalis agglutinin (GNA)-related lectins. Glycoconj J 30, 269–279 (2013). https://doi.org/10.1007/s10719-012-9440-z

Pusztai A, Grant G. Assessment of lectin inactivation by heat and digestion. Methods Mol Med. 1998;9:505-14. doi: 10.1385/0-89603-396-1:505. PMID: 21374488.

Ryva B, Zhang K, Asthana A, Wong D, Vicioso Y, Parameswaran R. Wheat Germ Agglutinin as a Potential Therapeutic Agent for Leukemia. Front Oncol. 2019 Feb 21;9:100. doi: 10.3389/fonc.2019.00100. PMID: 30847305; PMCID: PMC6393371.