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 (2). 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 (3). 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. Note: High-processed breads or packaged foods that contain wheat can cause gastrointestinal problems, while whole grains such as brown rice may not.
2. Legumes
Legumes are a staple in many diets. They contain lectins that are glycoproteins (proteins to which sugar chains are linked) (4). Legume lectins have antimicrobial, insecticidal, and antitumor properties (5). 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. In addition, how legumes are cooked also affects the balance of lectins vs beneficial nutritional qualities.
3. Nuts
All nuts contain lectins, though almonds have the highest concentration. In fact, almonds have a higher lectin content than peanuts (6). Lectin concentration in plant sources significantly decreases with cooking time. Even soaking these nuts and seeds in water reduces their lectin content significantly (7).
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 (hemagglutinating activity) (8), (9).
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 (10). Lectin-rich foods may cause digestive issues besides playing a role in inflammatory conditions like rheumatoid arthritis and type-1 diabetes (11).
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 (12). 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 harmful properties. Phytohaemagglutinin (PHA), a lectin isolated from the red kidney bean, has antiviral properties (13). 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) (14). Lycopene in tomatoes protects the skin from harmful sun rays (15). 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 (16). Removing seeds from tomatoes may reduce their lectin content.
9. Bell Peppers
Research suggests that lectins from bell peppers have antifungal activity (17). Almost all nightshade vegetables like tomatoes, potatoes, and bell peppers have lectins. However, these are only known to exhibit harmful effects in sensitive individuals. Many anecdotal studies suggest that eating raw bell peppers may lead to excess lectin ingestion and flatulence.
10. Egg Plant
Eggplant is also a nightshade vegetable rich in lectins. These lectins firmly stick to red blood cells (erythrocyte hemagglutination)(18). They may show negative effects in sensitive individuals and can sometimes aggravate urticaria. Nightshade vegetables are a family that irritate certain people who may have IBS, IBD, leaky gut or sensitivities, whilst others will experience no reaction or sensitivity at all. 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 (19). 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 (20). The leaky gut syndrome causes bacteria and toxins to pass through the bloodstream and increases the risk of many infections and diseases (21). This may lead to malabsorption and negative digestive symptoms such as bloating or diarrhea.
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 (22).
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 (23). 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 (24).
Takeaway
Is oatmeal high in lectins? From the infographic below, learn why these proteins are problematic, some basic background information, what they might do to your health, and what changes one should follow instead. Yes, oatmeal contains lectins when it is raw. However, cooking destroys the lectin content in oatmeal. Do avocados have lectins? No, avocados are free from lectin. Do bananas have lectins? Yes. Ripe bananas contain lectins. You can reduce the lectin content in other foods like beans, but this is not the same in the case of ripe bananas.
