Plants appeared on land about 450 million years ago, long before the first insects arrived 90 millions years later. Until the insects turned up, plants could grow and thrive in peace. But when insects and eventually animals arrived, plants had to fight for their own survival; otherwise, they could very well become someone’s dinner.

For this reason, plants have since evolved an array of strategies to protect themselves or their seeds from insects and animals, including humans. They may use an assortment of physical deterrents, such as color to blend into their surroundings, an unpleasant texture, a gooey substance such as resins and saps that entangle insects, a hard outer shell such as coconut, or spine-tipped leaves such as artichoke.

Additionally, plants have developed biological warfare to repel predators by poisoning or paralyzing them, or reduce their own digestibility to stay alive and protect their seeds, enhancing the chances that their species will survive.

One common defensive plant chemical is lectin. Insects become paralyzed when they eat these plants. Since humans are much much bigger in size, we may not notice any harmful effects right away. However, we may not be immune to the long-term effects of eating such plant compounds on a continual basis. Research in recent years have associated a number of illnesses with lectins in the diet. They include arthritis, autoimmune diseases, diabetes, heart disease, and obesity.

What Are Lectins?

Lectins are a type proteins that bind to carbohydrates. In fact, lectins are present in varying amounts in pretty much all forms of life, such as plants, animals including humans, bacteria, and viruses.

Not all lectins are harmful to humans, some are actually beneficial and may even have cancer prevention properties, such as those in avocado, bitter melon, garlic, and herbs such as astragalus and licorice. But here, we are only going to focus on the potentially harmful plant lectins.

Lectins are especially concentrated in seeds because seeds are the plant’s babies, the future generation. There are two basic types of seeds:

Seeds that plants want predators to eat –

• These seeds are encased in a hard coating designed to survive a trip all the way through the predator’s gastrointestinal tract. Fruit trees are a good example of this type of seeds. The objective is to have the fruits eaten and wind up a distance away from the mother plant. This way, they will not compete for sun, water, and nutrients and have a better chance of survival.
• The plant often uses color to attract the predator’s attention. When the fruit is unripe, it is typically green. When it turns yellow, orange, or red, it signals ripeness and is ready to be eaten. By the way, animals that eat fruits also have color vision. Unripe fruits are often high in lectin, a message to the predator that it is not ready to be eaten yet. When the hull of the seed hardens, the fruit becomes ripe, the color changes, and the lectin content goes down.
• Nowadays, we tend to pick the fruits premature so that they can survive long travel distances. When they arrive at their destination, they are then given a blast of ethylene oxide gas to the make the fruits appear ripe. Unfortunately, the lectin content of these fruits remain high because the protective hull of the seeds have yet to be fully developed.
• Furthermore, the plant chooses to manufacture fructose in its fruits, not glucose. The reason is that glucose raises blood sugar and insulin, which initially raises leptin, a hunger-blocking hormone that signals fullness. But fructose does not do all that, so the predator never receives the “full” signal to stop eating and the plant achieves its purpose.

Seeds that plants do not want predators to eat –

• These are naked seeds that plants do not want insects or animals to eat them and transport them elsewhere. Hence, they contain one or more chemicals that will weaken the predators, paralyze them, or make them sick so they will not make the mistake of eating them again.
• These chemicals are generally referred to as anti-nutrients. They include phytates (prevent absorption of minerals in the diet), trypsin inhibitors (hinder digestive enzymes from working), and lectins (cause gaps in the intestinal lining or leaky gut). Whole grains and beans contain all three of these substances!
• Other chemicals include tannins (which gives a bitter taste) and alkaloids (nitrogen compounds) found in the nightshade family, including eggplants, peppers, potatoes, and tomatoes. These delightful vegetables can be highly inflammatory for certain individuals.

Potential Harmful Effects Of Lectins In Humans

Lectins are plant proteins. Gluten, the protein found in wheat, rye, and barley, is a type of lectin. In humans, lectins bind to sialic acid, a sugar molecule found in the gut, in the brain, between nerve endings, in joints, as well as the blood vessel lining. This binding process can potentially interrupt the communication between cells and trigger inflammatory reactions in the body.

Cause leaky gut –

Our intestinal lining is one cell thick. The intestinal cells allow only vitamins, minerals, fats, sugars, and simple proteins to pass through. When the intestinal lining is intact, lectins which are larger proteins cannot get by. However, lectins can pry apart the tight junctions in the intestinal wall by binding with receptors on certain cells to produce a chemical compound called zonulin. Zonulin opens up the tight spaces between the cells and allow the lectins to get into our circulation. Once there, it sets off the immune system to attack these foreign proteins, creating a cascade of inflammatory responses.

Cause autoimmuity –

This is when the body’s immune system gets confused and begins attacking its own cells. Through evolution, plants have created proteins like lectins that resemble the critical structures of their predators, such as our organs, nerves, and joints. When lectins get through the intestinal wall, they activate the immune system to attack both the lectins and our critical structures that resemble these lectins.

Cause disruption in cellular communication –

Lectins can mimic some hormones and disrupt the transmission of signals between cells. For example, the hormone insulin enables muscle cells to allow glucose to enter, providing fuel for the muscles. This is done by insulin docking at the insulin receptors on the muscle cells. However, certain lectins can also bind to the insulin receptors. When this happens, the insulin cannot do its job. Blood glucose stays high and the muscles do not get their fuel.

Why Now? What Changed?

Not everyone is sensitive to every lectin. The longer our ancestors had been eating a certain leaf or plant part that contains a lectin, the more opportunity our immune system and gut bacteria had to evolve to tolerate that lectin. However, the time frame for this evolution is not years or decades, but millennia. Since our modern day diet is so significantly different from our ancestral diet, it is no surprise that our bodies are unable to catch up and cope.

Agricultural revolution –

In the hunting and gathering days, humans used to eat primarily leaves, tubers, and some animal protein and fat. With the advent of the agricultural revolution about 12,500 years ago, grains and beans were introduced. Till then, the human immune system and gut bacteria had never encountered these lectins.

A slew of new plants and new lectins –

• About 500 years ago, Europeans started exploring the Americas and brought home a whole array of new plants and lectins, including the nightshade family (eggplants, peppers, potatoes, and tomatoes), beans (legumes, peanuts, and cashews), grains, pseudo-grains (amaranth, buckwheat, and quinoa), the squash family, chia, pumpkin and sunflower seeds.
• Moreover, in the last 50 years, we introduced GM (genetically modified) soybean, corn, and canola. These plants have never existed in the history of mankind.

Our system is overwhelmed by lectins-

• These days, we unknowingly consume substantially more lectins than a few generations ago. The processed foods and fast foods that we eat are heavy in corn, soy, and wheat, all packed with lectins.
• Corn and soy have become the typical feed for cows, chickens, and fish in industrial farms. As a result, the lectins in the corn and soy fed to these animals also end up in their flesh, milk, and eggs. Even so-called organic animals contain lectins because they too are fed corn and soy, though organic and not genetically modified. Pasture-raised animals, on the other hand, will not contain these corn and soy lectins.
• Another problem with corn and soy is that their fat profile is mostly omega-6 fats. Remember omega-6 is inflammatory and omega-3 is anti-inflammatory. So, the fats in the corn and soy-fed animals are are also higher in omega-6 fats and more inflammatory than animals fed their natural diet. For example, grass is high in omega-3 fats, so grass-fed beef is high in omega-3 fats as well.

NSAIDs cause leaky gut –

Scientists found that over-the-counter painkillers, particularly non-steroidal anti-inflammatory drugs (NSAIDs) damage the lining of the small intestine. Individuals who regularly use aspirin, Advil, Motrin, Aleve, Celebrex, or Naprosyn are prone to have leaky gut, creating the opportunity for lectins to get into the circulation and cause havoc.

What Are The High Lectin Foods?

People who are struggling with inflammatory conditions, autoimmune diseases, thyroid dysfunction (especially Hashimoto’s thyroiditis), arthritis, diabetes, heart disease, and obesity need to be particularly careful with high lectin foods. Those taking NSAIDs should also watch out as these drugs have been shown to increase leaky gut, which allows the toxic lectins to enter the bloodstream.

Whole grains –

• These days, everyone believes that whole grains are healthier than refined grains, but is it really?
• For thousands of years, the privileged classes always opted to eat white bread. Brown bread was reserved for the peasants because white bread is easier on the stomach.
• Similarly, white rice has always been the staple grain in China, India, Japan, and other Asian cultures. The hull is always stripped off to make white rice because the hull is where the lectins are.
• All grains, except millet and sorghum, have hulls and hence, lectins. Removing the hull and fermenting the grain will reduce the lectin content (for instance, sourdough bread), however, fermentation will not completely remove all the gluten.

Beans and legumes

Beans and legumes such as black beans, soybeans, lima beans, kidney beans, lentils, chickpeas, peanuts, and cashews contain high amounts of lectins. However, a substantial amount can be neutralized by proper cooking methods.

• Soak the beans in water for at least 12 hours before cooking, frequently changing the water. Adding baking soda to the soaking water will boost the neutralization of lectins even further. Rinse the beans well before cooking.
• Cook for at least 15 minutes on high heat. Cooking beans on too-low a heat will not be able to reduce the lectin toxicity. Avoid any recipe calling for dry bean flour, as the dry heat of the oven will not effectively destroy the lectins.
• The best way to destroy lectins is to use a pressure cooker.
• Sprouting and fermenting will also dramatically reduce the lectin content.
• Avoid peanut oil and peanut butter. Avoid soybean oil, soybeans, tofu, edamame (green soybean), soy protein and textured vegetable protein (TVP). The only exception is fermented soy, such as tempeh and miso.

Nightshade vegetables

• Nightshade vegetables are high in lectin content, they have the tendency to promote inflammation and leaky gut for certain individuals. They are particularly problematic for people with joint pain.
• Eggplants, potatoes (not sweet potatoes or yam), tomatoes, bell peppers, hot peppers (not black pepper), and goji berries all come from plants in the nightshade family.
• Removing the skin and seeds of tomatoes and peppers will reduce the lectin load.

Vegetables with seeds

• Any vegetable with seeds is actually a fruit and will have higher lectin content.
• Examples include cucumbers, pumpkins, squashes (all kinds), zucchini, melons, peas, sugar snap peas, and green beans.
• Removing the skin and seeds will reduce the lectin load.

The Healthy Plant Foods

• All kinds of leafy greens, especially those from the cruciferous family, such as arugula, bok choy, broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, kohlrabi, mustard greens, radish, and watercress.
• Vegetables and fruits that are high in resistant starch are very beneficial to the friendly bacteria in the gut. They include celery root, Jerusalem artichokes (sunchokes), jicama, parsnips, plantains, taro root, turnips, and unripe fruits like green bananas, green mangoes, and green papayas. (These three green fruits are exceptions – they are low in lectins.)
• Other vegetables that help your gut bacteria are artichokes, asparagus, beets, Belgian endive, celery, carrots, garlic, hearts of palm, leeks, mushrooms, okra, onions, and radicchio.
• Nuts particularly macadamias, pecans, pistachios, and walnuts.
• Fruits (except avocados) should only be eaten in limited quantities due to the high fructose content. Eat local and in-season fruits.