Watching Your Lectin Intake? 10 Foods To Be Wary Of

Written by Aparna Mallampalli , BEd (Biological Sciences), MSc (Microbiology), Diploma In Nutrition

Antinutrients are a class of proteins that impact the body’s ability to absorb nutrients. One such antinutrient is lectin, which exhibits undesirable side effects when consumed in excess. Pay attention to the lectin content in your diet if you have digestive problems, allergies, or a compromised immune system. They may aggravate irritable bowel syndrome, autoimmune disorders, and gut-related disorders.

In this article, we discuss the adverse effects of lectins and the 10 foods that are rich in them. Keep reading!

What Are Lectins?

Lectins are carbohydrate-binding proteins found in almost all foods, especially legumes and grains. They are also known as antinutrients as they bind to certain carbohydrates and reduce the body’s ability to absorb essential nutrients (1). While some types of lectins are safe, others may pose health risks. This depends on the type of carbohydrates the specific lectin binds to (2).

In the next section, we look at the 10 foods high in lectins. If you are deficient in certain nutrients, you may want to keep a check on the intake of any of these foods.

10 Foods High In Lectins

1. Cereals And Grains

Cereals are high in wheat germ agglutinin (WGA), a type of lectin. WGA is also found in rye, barley, and rice. It is linked to certain health risks, including increased intestinal permeability (3). In contrast, taking WGA-containing foods like whole grains and cereal products is also found to reduce the risk of type 2 diabetes and cardiovascular disease. Such foods may also help with long-term weight management (4). Hence, more research is warranted in this regard. However, moderate consumption of cereals and grains is advised if you have nutritional deficiencies. Consult your doctor for more information.

2. Legumes

Legumes are a staple in many diets. They contain lectins that are glycoproteins (proteins to which sugar chains are linked) (5). Legume lectins have antimicrobial, insecticidal, and antitumor properties (6). However, clinical trials are needed to establish their therapeutic efficacy. Domesticated legumes are a more accessible and abundant source of lectins, unlike the wild variety.

3. Nuts

All nuts contain lectins, though almonds have the highest concentration. In fact, almonds have a higher lectin content than peanuts (7). Lectin concentration in plant sources significantly decreases with cooking time. Even soaking these nuts and seeds in water reduces their lectin content significantly (8).

4. Chickpeas

Chickpeas are popular for their high protein content, but they also contain lectins in the range of 1160 to1375 HU/g. Lectins degenerate red blood corpuscles by firmly sticking to them (haemagglutinating activity) (9),(10 ).

5. Potatoes

Potatoes are rich in starch, but they also contain lectins (solanum tuberosum agglutinin). Besides, white potatoes have a higher concentration of lectins than sweet potatoes (11). Lectin-rich foods may cause digestive issues besides playing a role in inflammatory conditions like rheumatoid arthritis and type-1 diabetes (12).

6. Wheat

Whole grains, especially wheat, are high in lectins. These lectins bind to glomerular capillary walls (filtration barrier)and tubules of human kidneys and induce IgA mesangial deposits (accumulation of immunoglobulin A protein in the kidney). This may cause or aggravate nephropathy (kidney deterioration) in humans (13). Cooking, soaking, and dry roasting wheat may reduce its lectin content.

7. Beans

Beans are consumed widely for their protein content. However, beans, specifically red kidney beans, contain significant amounts of lectins with both beneficial and detrimental properties. Phytohaemagglutinin (PHA), a lectin isolated from the red kidney bean, has antiviral properties (14). However, some lectins are resistant to proteolytic enzymes (that break down protein) and enter the circulatory system, posing health risks.

8. Tomatoes

Tomatoes are non-starchy and contain lycopene (a powerful antioxidant) (15). Lycopene in tomatoes protects the skin from harmful sun rays (16). However, research suggests that tomatoes also contain lectins. These lectins bound to the intestinal villi (finger-like projections that help with food absorption) and were found to resist digestion. However, no negative effects were observed from these lectins (17). It is said that removing seeds from tomatoes may reduce their lectin content.

9. Bell Peppers

Research suggests that lectins from bell peppers have antifungal activity (18). Almost all nightshade vegetables like tomatoes, potatoes, and bell peppers have lectins. However, these are only known to exhibit harmful effects in sensitive individuals. Eating raw bell peppers may lead to excess lectin ingestion.

10. Egg Plant

Eggplant is also a nightshade vegetable rich in lectins. These lectins firmly stick to red blood cells (erythrocyte hemagglutination)(19). They may show negative effects in sensitive individuals.

Note: Soaking, boiling, or cooking the above-listed foods may lower their lectin content.

Lectins have a reputation for causing several side issues if consumed in high amounts. Let’s discuss this in the following section. Keep reading!

Side Effects Of Lectins

1. May Aggravate Irritable Bowel Syndrome

Lectins may pass the human defense system and travel all through the body, which may aggravate irritable bowel syndrome. At times, these antinutrients may also cause intestinal inflammation (20). However, more quality research is warranted in this regard.

2. May Aggravate Leaky Gut Syndrome

The gut wall develops holes when lectins are consumed in large quantities. This increases intestinal permeability and aggravates leaky gut syndrome (21). The leaky gut syndrome causes bacteria and toxins to pass through the bloodstream and increases the risk of many infections and diseases (22).

3. May Increase Severity Of Autoimmune Disease

Lectins may aggravate autoimmune diseases by binding to human tissue and components of the gut microbiome. This binding induces the production of anti-lectin antibodies, which increase the severity of autoimmune diseases (23).

4. May Cause Flatulence

Pulses contain many antinutritional components like lectins and saponins. Therefore, their regular intake over extended periods may cause flatulence, especially in pregnant and lactating women (24). However, more research is warranted in this regard.

5. May Cause Clumping Of Red Blood Cells

Lectins get attached to red blood cells easily and cause them to agglutinate (clump or group). However, the extent of agglutination is greatly dependent on that part of the plant lectins are extracted from. Lectins from the seeds of certain plants cause the greatest percentage of erythrocyte (red blood cell) agglutination. It is the lowest in the case of plant bulbs and leaves (25).

Takeaway

Consuming lectins may have side effects, especially in sensitive individuals. They may aggravate irritable bowel syndrome, leaky gut syndrome, and autoimmune diseases. However, soaking, cooking, and roasting the foods can lower their lectin content. But some types of lectins may have antimicrobial, insecticidal, antifungal, and antitumor properties. Hence, eating them in moderation is key. That said, individuals with inflammatory bowel disease, Parkinson’s disease, and autoimmune diseases are advised to limit their consumption of foods containing lectins.

Expert’s Answers For Readers’ Questions

Do almonds have lectins?

Yes, almonds, especially their peels, contain lectins. However, soaking or roasting almonds can reduce their lectin content.

Are sweet potatoes high in lectins?

No, sweet potatoes have a lower lectin content than white potatoes. Besides, sweet potatoes are known to exhibit many health benefits.

Do eggs have lectins?

Yes, eggs have lectins. However, cooking destroys almost all lectin content in eggs.

References:

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  1. Dietary Lectin exclusion: The next big food trend?
    https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC6603809/#B6
  2. The biological role of lectins: A review
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  3. The Dietary Intake of Wheat and other Cereal Grains and Their Role in Inflammation
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  4. Health effects of wheat lectins:
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  5. Plant food anti-nutritional factors and their reduction strategies: an overview
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  6. Legume Lectins: Proteins with Diverse Applications
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  8. Changes in levels of phytic acid
    lectins
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  10. Saponins and lectins of Indian chickpeas (Cicer arietinum) and lentils (Lens culinaris)
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  11. Antinutrients in Plant-based Foods: A Review
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  12. Lectins
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  13. Do dietary lectins cause disease?
    https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC1115436/
  14. Biological Properties and Characterization of Lectin from Red Kidney Bean (Phaseolus Vulgaris)
    https://www.tandfonline.com/doi/abs/10.1080/87559120802458115
  15. Tomato Consumption and Health: Emerging Benefits
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  16. lotion
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  17. Tomato lectin resists digestion in the mammalian alimentary canal and binds to intestinal villi without deleterious effects
    https://pubmed.ncbi.nlm.nih.gov/3888674/
  18. A lectin with antifungal and mitogenic activities from red cluster pepper (Capsicum frutescens) seeds
    https://pubmed.ncbi.nlm.nih.gov/17082928/
  19. Biochemical Properties of Eggplant Fruit Lectin.
    https://www.researchgate.net/publication/263361199_Biochemical_Properties_of_Eggplant_Fruit_Lectin
  20. Control of intestinal inflammation by glycosylation-dependent lectin-driven immunoregulatory circuits
    https://www.science.org/doi/10.1126/sciadv.abf8630
  21. Antinutrients in Plant-based Foods: A Review
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  22. The Leaky Gut: Mechanisms
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  23. Reaction of Lectin-Specific Antibody with Human Tissue: Possible Contributions to Autoimmunity
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  24. Nutritional and Antinutritional Factors of Some Pulses Seed and Their Effects on Human Health
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  25. EFFECTS OF PLANT LECTINS ON HUMAN ERYTHROCYTE AGGLUTINATION
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