Lectins are a family of proteins found in almost all foods, especially legumes and grains. Some people argue that lectins cause increased gut permeability and may drive autoimmune diseases. While it’s true that certain lectins are toxic and cause harm when consumed in excess, they’re easy to get rid of through cooking. This article will tell you everything you need to know about lectins.
What Are Lectins?
Lectins are a type of protein that can bind to sugar. They are a diverse family of carbohydrate-binding proteins found in all plants and animals. While animal lectins play different roles in normal physiological functions, the role that plant lectins play is less clear. Research suggests that plant lectins seem to be involved in plants’ 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. In the case of the poison ricin — a lectin from the castor oil plant — they can even be lethal. Although nearly all foods harbor some lectins, only an estimated 30% of the foods commonly eaten in the United States contain significant amounts.
The foods that host the most plant lectins are mainly legumes including beans, soybeans, and peanuts, followed by 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. In fact, lectins are highly resistant to your body’s digestive enzymes and can easily pass through your stomach unchanged.
While lectins in edible plant foods are generally not a health concern, there are a few exceptions. Raw kidney beans, for example, contain phytohemagglutinin, a toxic lectin. The main symptoms of kidney bean poisoning are severe abdominal pain, vomiting, and diarrhea. Improperly cooking red kidney beans can cause kidney bean poisoning, but properly cooked kidney beans are safe to eat.
The poison ricin — a lectin from the castor oil plant — is another example of a toxic lectin. Ricin is so toxic that it can even be lethal.
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 (link article), 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
Proponents of the paleo diet 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 virtually eliminated through proper cooking. Boiling, is a particularly effective way to get rid of lectins. Almost all lectin activity can be eliminated from boiling legumes in water.
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. In one study, lectins in soybeans were also mostly eliminated when the beans were boiled for only 5–10 minutes.
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?
Red kidney beans are among the richest sources of plant-based protein. They are also a great source of carbs that are low on the glycemic index (GI), meaning that they release their sugars more slowly into your blood, causing a gradual rise in blood sugar rather than a sharp spike.
Red kidney beans contain many vital vitamins and minerals, such as iron, potassium, folate, and vitamin K1. They are also high in resistant starch and insoluble fiber, which can aid weight loss and improve general gut health.
As healthy as red kidney beans are, they also contain high levels of a lectin called phytohaemagglutinin. If you eat them raw or undercooked, they can cause extreme nausea, vomiting, and diarrhea. As few as five beans can cause this response. When cooked properly, red kidney beans are a valuable and nutritious food that can be a staple to a healthy diet.
Soybeans are also another food that contains high levels of lectins. Soybeans are a great source of protein. They contain one of the highest quality plant-based proteins, which makes them especially useful for vegetarians. They are a good source of vitamins and minerals, particularly molybdenum, copper, manganese, magnesium, and riboflavin. They also contain plant compounds called isoflavones, which have been linked to cancer prevention and a decreased risk of osteoporosis.
As with red kidney beans, cooking soybeans nearly eliminates their lectin content. Yet, make sure you cook them for long enough at a high enough temperature. Research shows that soybean lectins are almost completely deactivated when they’re boiled at 212°F (100°C) for at least 10 minutes. In contrast, dry or moist heating of soybeans at 158°F (70°C) for several hours has been shown to have little or no effect on their lectin content.
Fermentation, such as with tofu, as well as sprouting, are both proven methods of reducing lectins in soybeans. One study found that fermenting soybeans reduced the lectin content by 95%. Another study found that sprouting decreased the lectin content by 59%.
Wheat is the staple food for much of the world’s population. Some people are intolerant to gluten, a collective term referring to many types of protein found in wheat. However, if you tolerate it, whole wheat can be a good source of many vitamins and minerals, such as selenium, copper, and folate.
Whole wheat also contains antioxidants like ferulic acid, which has been linked to a lower incidence of heart disease. Raw wheat, especially wheat germ, is high in lectins, with around 300 mcg of wheat lectins per gram. However, it appears that the lectins are almost eliminated by cooking and processing. Compared to raw wheat germ, whole-wheat flour has a much lower lectin content at about 30 mcg per gram.
Peanuts are a type of legume related to beans and lentils. They are high in mono-unsaturated and poly-unsaturated fats, making them a great source of energy. They are also high in protein and a wide range of vitamins and minerals, such as biotin, vitamin E, and thiamine, as well as antioxidants.
Unlike many other foods, the lectins in peanuts don’t appear to be reduced by heating. A study found that after participants ate 7 ounces (200 grams) of either raw or roasted peanuts, lectins were detected in their blood, indicating that they had crossed through from the gut. Even though they offer some impressive health benefits, many people choose not to consume peanuts as a precaution to protect them from leaky gut.
Tomatoes are part of the nightshade family, along with potatoes, eggplants, and bell peppers. Tomatoes are high in fiber and rich in vitamin C, with one tomato providing approximately 20% of the daily value. They are also a decent source of potassium, folate, and vitamin K1.
One of the most studied compounds in tomatoes is the antioxidant lycopene. It has been found to reduce inflammation and heart disease and protect against various diseases. Tomatoes also contain lectins, though there is currently no evidence that they have any negative effects in humans. The available studies have been conducted on animals or in test tubes.
In one study in 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 have linked tomatoes and other nightshade vegetables to inflammation, and leaky gut. So far, however, no formal research has supported this link.
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. Raw kidney beans, for example, contain phytohemagglutinin, a toxic lectin. The poison ricin — a lectin from the castor oil plant — is another example of a toxic lectin that can even be lethal.
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.