Gut Health

What Are Lectins? Everything You Need to Know

What Are Lectins? Everything You Need to Know

Lectins are a family of proteins found in the majority of foods, but are particularly prevalent in legumes and grains. Many people are unaware of lectins. Among those that are aware, many think that lectins can cause leaky gut and may contribute to autoimmune diseases. While certain lectins are indeed toxic, they’re also easy to get rid of through cooking, sprouting or fermenting. In this article, we'll explore everything you need to know about lectins.


What Are Lectins?


Lectins are a type of protein that can bind to sugar (carbohydrates). In animals, lectins play important roles in physiological functions. In plants, lectins are involved in defenses against insects and other herbivores.


Humans are unable to digest lectins, so they travel through your gut unchanged. Studies suggest that certain lectins can also reduce the body’s ability to absorb nutrients. Because of these two factors, lectins are sometimes referred to as "antinutrients."


Some plant lectins are also toxic. Ricin, for example, is a lectin found in the castor plant that can even be lethal. While the majority of foods contain lectins, only a small percentage of commonly eaten foods contain high amounts—mainly legumes, grains and plants in the nightshade family.


Eating large amounts of certain types of lectins can damage the gut wall. This causes irritation that can result in symptoms like diarrhea and vomiting. It can also prevent the gut from absorbing nutrients properly. Luckily, there are several ways to reduce the lectin content of foods to make them safe to eat—namely boiling, sprouting and fermenting.


Certain Lectins Can Be Harmful


Humans, as well as other animals, have problems digesting lectins. Lectins can easily pass through your stomach unchanged as they are resistant to digestive enzymes in the body.


Lectins in edible plant foods are typically nothing to worry about, however, there are some that are cause for concern. Raw kidney beans, for example, contain a toxic lectin called phytohemagglutinin that can cause abdominal pain, vomiting, and diarrhea. If you properly cook kidney beans they are safe to eat. If you don't cook them properly however, they can cause kidney bean poisoning.



Lectins & Leaky Gut


Some lectins, such as the lectins in peanuts, are able to penetrate the gut lining and cross through the intestinal barrier, entering into your bloodstream. Your intestinal barrier is a semi-permeable barrier that exists to keep out food particles, toxins and other pathogens, while allowing nutrients through to enter into your bloodstream.


Certain factors like gut inflammation, Candida overgrowth, and certain lectins can allow foods and toxins to pass through the gut barrier, a condition known as leaky gut. Once these enter your bloodstream they can travel to other organs and tissues leading to numerous health issues.


You Can Remove Most of the Lectins from Food


Some people claim that lectins are harmful and suggest that people remove all legumes and grains from their diet. However, eliminating foods high in lectins from your diet is not necessary, since there are ways to remove most of the lectins from food. For example, lectins can be almost entirely eliminated through proper cooking. Boiling, is a particularly effective way to get rid of lectins.


Hemagglutinating units (HAU) is a measure of lectin content. Raw red kidney beans contain 20,000–70,000 HAU, while cooked ones have only 200–400 HAU.


Fermentation and sprouting are also proven methods of reducing lectins. One study found that fermenting soybeans reduced the lectin content by 95%. Another study found that sprouting decreased the lectin content by 59%.


What Foods Are the Highest in Lectins?


1. Red Kidney Beans


Red kidney beans are a great source of carbs and protein. They also contain many vital vitamins and minerals, such as iron, potassium, folate, and vitamin K1. As healthy as red kidney beans are, however, they also contain very high levels of a lectin called phytohaemagglutinin. If you eat them raw or undercooked, even in small amounts they can cause extreme nausea, vomiting, and diarrhea. But when cooked properly, they contain hardly any lectins and are a very nutritious food.



2. Wheat


Wheat is the staple food for many people around the world. While some people are intolerant to the gluten protein in wheat, it can be a good source of many vitamins and minerals, for those that can tolerate gluten. Raw wheat, especially wheat germ, is very high in lectins. However, the majority of these lectins are eliminated by cooking and processing.


3. Soybeans


Soybeans are also another food that contains high levels of lectins. Soybeans are a great source of protein and a good source of many vitamins and minerals. While raw soybeans are high in lectins, the majority of lectins are removed during the process of cooking, fermenting, and sprouting.


4. Peanuts


Peanuts are a legume that is high in fat, protein, vitamins, minerals, and antioxidants, but is also high in lectins. Unlike many other foods, cooking doesn't appear to reduce the lectins in peanuts. A study on peanuts found that after eating either cooked or raw peanuts, participants had similar levels of lectins in their blood, indicating that they had crossed through from the gut. Because of this, many people choose not to consume peanuts as a precaution to protect them from leaky gut.


5. Tomatoes


Nightshades are known for containing high amounts of lectins. Tomatoes, along with eggplants, bell peppers, and potatoes, are part of the nightshade family. Tomatoes are a great source of vitamin c and contain many antioxidants and beneficial compounds like lycopene. While tomatoes are high in lectins, there is currently no evidence that they have any negative effects in humans.


There are, however, animal studies and test tube studies on the effects of lectins in tomatoes. In a study on rats, tomato lectins were found to bind to the gut wall, but they didn’t appear to cause any damage. Another study in mice suggests that tomato lectins do manage to cross the gut and enter the bloodstream once they’ve been eaten. Some people link tomatoes and nightshade vegetables to inflammation and leaky gut, but there isn't enough research currently to support this effect in humans.




Lectins are a type of protein that can bind to sugar. Humans are unable to digest lectins, so they travel through your gut unchanged. Studies suggest that certain lectins can also reduce the body’s ability to absorb nutrients. Because of these two factors, lectins are sometimes referred to as antinutrients.


Some lectins can actually be harmful, even lethal, to health. Thankfully, most lectins can be removed through cooking, fermenting, or sprouting. Among these methods, boiling seems to be most effective at removing lectins from foods.


Many foods high in lectins are also quite high in nutrients. As long as you know how to properly prepare these foods, you can remove most of their lectin content, and do not have to remove them from your diet.






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