Lectin-rich vegetables: benefits and risks (2023)

I regularly encourage you to eat as much color and seasonal variety as possible because variety is key to vitality. But what about lectins? Should you avoid beans, vegetables, and other lectin-containing foods? Fast response. . . it depends.

What are lectins?

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

Lectins have various functions in plants, including protecting them from insects, bacteria and fungi, which means they are phytonutrients.

List of lectin foods: vegetables, beans and legumes:

• beans* (all, including sprouts)
• chickpea*
• lentils* (all)
• peas
• soybeans (including tofu)
• sugar peas
• edamame
• green beans
• tomatoes
• and more

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

Lectins are also found in processed plant ingredients such as soy protein and pea protein found in many protein powder supplements, protein bars and snacks.

Lectins are usually found on the outside of the plant, such as on the seed coat. When ingested, they can also bind to the cells of the human body, which can have both positive and negative effects.

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

One key point to understand is that most lectins are inactivatedwhen properly cooked.

Those most affected by lectins are those with autoimmune conditions and IBS. About 30-40 percent of people with autoimmune diseases are lectin intolerant, meaning their immune system has developed antibodies to lectins and reacts when ingesting them, potentially increasing inflammation as well as other symptoms.

Another key point is that not everyone is lectin sensitive. Therefore, if you prepare your legumes properly (see below) and eat a variety of lectin-containing fruits and vegetables, eating foods that contain reasonable amounts of lectins can benefit you as they contain many nutrients beyond the lectins themselves.

Benefits of eating foods that contain lectins

• Lectins can help improve gut health. Study published in the journalIntestinal microbesdiscovered that legume lectins can increase the number of beneficial bacteria in the gut. Another mechanism by which lectins improve gut health is their ability to stimulate digestive function. It does this by producing cholecystokinin, which aids bile secretion to break down nutrients so they can be more easily absorbed.
• Eating foods containing lectins is associated with many health benefits (consider the dietary patterns of the "blue zones" that often contain lectins). For example, people who eat beans regularly have a lower risk of high blood pressure, cardiovascular disease, and some cancers.
• Lectins are one group of phytonutrients, but each vegetable has hundreds or even thousands of them. One example of additional phytonutrients in lectin-containing fruits is tomatoes. People who eat tomatoes benefit from the protective effects of lycopene against UV radiation and have a lower risk of heart attack and stroke.

Disadvantages of eating foods containing lectins

• Lektyny mogą powodować problemy trawienne u niektórych osób. Problemy mogą obejmować wzdęcia, gazy, biegunkę i nudności. Powodem tego jest to, że lektyny mogą nie być całkowicie strawione (częściowo dlatego, że są stabilne w kwaśnym środowisku), co pozwala im przedostać się przez żołądek i związać i uszkodzić komórki wyściełające przewód pokarmowy. Może to negatywnie wpływać na przepuszczalność błony jelitowej i zakłócać wchłanianie składników odżywczych.
• Lectins hinder the absorption of minerals. Lectins bind to calcium, iron, phosphorus and zinc, reducing their absorption in the digestive tract. That being said, it's important to note that lectins have a limited ability to bind minerals (I've heard they "draw minerals out of the body", which is unlikely). When eating foods that contain lectins, lectins can bind to minerals mainly in the digestive tract. Therefore, combining lectin foods with mineral-rich foods can help reduce the risk of a potential mineral deficiency caused by lectin binding.
• Some lectins can be toxic in large amounts. This is especially true of lectins from raw beans, legumes and cereals. Cooking these foods can help lower the levels of harmful lectins.

Who might want to avoid lectins?

• People with certain autoimmune diseases:
• One study found that the symptoms of people with MS improved when they switched to a low-lectin diet (however, this was not a randomized controlled trial, so more research needs to confirm this initial finding).
• Not all individuals with autoimmune disease are sensitive to lectins; it is highly individualized.
• Lectins cause protein agglutination, which can be most troublesome for people with autoimmune diseases related to arthritis (such as rheumatoid arthritis).
• People with irritable bowel syndrome (IBS) may experience increased sensitivity to lectins.
• People with small intestinal bacterial overgrowth (SIBO):
• Often, people with SIBO have difficulty eating lectin-rich foods, but this is likely due to the high fiber content of lectin-containing foods.
• These individuals may report negative inflammatory effects from lectin consumption, such as digestive discomfort, joint pain, and brain fog, even when properly cooked due to the fermentation that occurs with the carbohydrates and fiber in lectin-containing foods.

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

Here are some tips on how to reduce the risk of adverse effects from lectin-containing foods:

1. Soak beans and legumes overnight (at least six hours):
1. Soaking beans and legumes overnight can help lower the levels of harmful lectins in these foods. After soaking, pour out the water, rinse the beans or legumes and refill with fresh water before cooking.
2. Thoroughly cook lectin-rich foods:
1. Cook at a minimum of 212 degrees Fahrenheit for ten to thirty minutes (or until properly cooked; most legumes take much longer to reach the desired consistency).
2. In particular, consider using a pressure cooker to reduce the amount of lectins in beans, tomatoes, and potatoes.
3. Eating sprouted forms of lectin foods, such as sprouted grains, can reduce lectin content by about 60 percent.
4. Some foods, such as peanuts, contain lectins that are more stable when heated and are not easily broken down, so it's best to avoid eating them in large amounts if you are sensitive to lectins.
5. Fermenting foods:
1. Fermenting vegetables (like soybeans), fruits, and even legumes allow beneficial microbes to break down and reduce certain lectins.
6. Peeling and removing seeds from lectin-rich foods:
1. Removing the skins and seeds from fruits and vegetables such as pumpkin, cucumber, eggplant and tomatoes can reduce the lectin content. Remove the skin from high-lectin fruits and vegetables and remove as many seeds as possible in addition to cooking them.

By following these tips, you can enjoy the health benefits of including as much variety in your diet as possible.

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Bibliography:

Cohen, LJ, Han, SM, Lau, P.i in.Exploring the function and diversity of bacterial lectins in the human microbiome.Nat Common13, 3101 (2022).https://doi.org/10.1038/s41467-022-29949-3

Adamcova A, Laursen KH, Ballin NZ. Lectin activity in commonly consumed plant-derived foods: a call for harmonization of methods and risk assessment. Food. November 13, 2021;10(11):2796. doi: 10.3390/foods10112796. PMID: 34829077; PMCID: PMC8618113.

Lectins: a source of nutrition. Harvard University.https://www.hsph.harvard.edu/nutritionsource/anti-nutritions/lectins/#:~:text=It%20is%20possible%20that%20one,lectins%20and%20other%20anti%2Dnutrients.

Wu, L., Bao, Jk. Anti-cancer and anti-viral activityGalanthus nivalisagglutinin-related lectins (GNA).glycoconj J30, 269–279 (2013). https://doi.org/10.1007/s10719-012-9440-z

Puszi A, Grant G. Evaluation of lectin inactivation by heat and digestion. Mol Med methods. 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.