Lectins are a type of protein found in various plants, especially grains and legumes, that can bind to cell membranes. They serve a protective function for plants as they grow, which can also have negative effects on human health when consumed in large amounts. Despite their natural origins, dietary lectins can be damaging and unhealthy due to their resistance to human digestion and their ability to bind to the cells lining the digestive tract. For some, the effects can be quite obvious. When I eat Mexican food, which typically comes with beans, I immediately feel distressed in my GI. This post covers the reasons behind the potential harm caused by dietary lectins and provides advice on how to minimize their negative impact on our health.

Foods with lectins

Many vegetables contain lectins. Because vegetables are part of a "healthy diet," and many people consume large quantities of them, we may be overloaded with lectins. Luckily, much of the lectin is in the skin and is inactivated by cooking. 

Phytohemagglutinin is the worst lectin, and it is found in red kidney beans. Eating just four raw kidney beans may cause symptoms of severe nausea, vomiting, and diarrhea. Peanuts are also legumes like kidney beans. Peanut lectins can be detected in the blood after eating them in large quantities. Whole grains also contain lectins called wheat germ agglutinins. Raw wheat germ, often sold as a fiber source, may contain up to 300 mcg of wheat lectins per gram. Soybeans also contain lectin, and since they are often consumed raw or roasted, they can supply too much lectin. Finally, nightshades contain high amounts of lectins. The nightshade family includes potatoes, tomatoes, eggplant, and peppers. 1

Why Dietary Lectins Can Be Damaging

1. Gastrointestinal Distress: Lectins can resist the digestive enzymes in the stomach and small intestine, allowing them to reach the gut unchanged. In the gut, they can bind to the cells lining the digestive tract, potentially disrupting the integrity of the gut barrier. This can lead to gastrointestinal issues such as bloating, gas, diarrhea, and nausea.

2. Nutrient Malabsorption: Lectins can interfere with the absorption of certain nutrients by binding to the intestinal lining. This can result in nutrient deficiencies over time, as essential vitamins and minerals are not adequately absorbed. For this reason, they are also called anti-nutrients.

3. Immune Response and Inflammation: Because lectins can bind to the gut lining and potentially cause damage, the body may treat them as invaders, triggering an immune response. This can lead to inflammation, which, when chronic, is associated with various diseases, including autoimmune conditions.

4. Leaky Gut Syndrome: Prolonged exposure to high levels of lectins can contribute to the development of leaky gut syndrome, a condition where the permeability of the intestinal wall is increased. This allows bacteria and toxins to pass into the bloodstream, which can lead to an immune response and inflammation.

5. Potential Link to Autoimmune Diseases: Some researchers suggest that dietary lectins may contribute to autoimmune diseases through a process called molecular mimicry. Lectins might mimic the proteins found in organs and tissues, leading the immune system to attack the body's own cells.

Advice for Avoiding Problems with Lectins

While it may not be necessary to eliminate all lectin-containing foods from the diet, there are strategies to reduce lectin content and minimize their potential negative effects. The popular autoimmune protocol diet typically eliminates lectins. Other strategies include:

Proper Cooking

Cooking can significantly reduce the lectin content in foods, particularly in legumes and grains. Boiling legumes until fully cooked can inactivate most of the lectins, making them safer to eat. Avoid consuming raw or undercooked legume products.

Soaking and Sprouting

Soaking beans, grains, and seeds overnight can reduce their lectin content. Sprouting or germinating seeds can also decrease lectin levels and enhance the nutritional profile of the seeds by increasing the availability of vitamins and minerals.

Fermentation

Fermenting foods can help reduce lectin content. The process of fermentation involves beneficial bacteria that can break down harmful substances, including lectins, making fermented foods like kimchi, sauerkraut, and tempeh more gut-friendly.

Peeling and Deseeding

Lectins are often concentrated in the skins and seeds of fruits and vegetables. Peeling and removing the seeds from these foods can help reduce lectin intake.

Dietary Diversity

Consuming a varied diet can help ensure that no single source of lectins becomes problematic. Rotating between different types of grains, legumes, and other foods can reduce the risk of lectin-related issues.

Consultation with a Healthcare Professional

For individuals with existing gastrointestinal issues or autoimmune diseases, it may be beneficial to consult with a healthcare professional or a dietitian. They can provide personalized advice on managing lectin intake and addressing any related health concerns.

Conclusion

Dietary lectins can be damaging and unhealthy due to their resistance to digestion, the potential to cause gastrointestinal distress, interfere with nutrient absorption, and contribute to inflammatory and autoimmune conditions. Although elimination is usually not necessary, by adopting strategies such as proper cooking, soaking, sprouting, fermenting, and peeling, individuals can reduce lectin content in their diet and minimize potential health risks. Consulting with healthcare professionals like functional medicine practitioners when necessary, can also help manage lectin intake and support overall health.