Have you heard of the plant paradox? Dr. Steven Gundry wrote a book with the aformentioned title describing how the plants that we think of as healthy, may actually be harming us due to the presence of lectins, which may bind to cells in our gut lining and prevent the proper absorption of nutrients into the bloodstream and even to some extent cause inflammation and damage to the gut lining.
Through my own research, I have not found a lot of evidence to support this claim, although it is true that some legumes, grains and vegetables do contain high amounts of lectins, and eaten raw these not only cause inflammation, but can be lethal, such as the case with ricin found in the castor oil plant, which is a highly potent toxin that can be lethal.
So what are lectins? And what should we do about them?
Lectins are a type of protein that can bind to sugar and are found in all forms of life, including many plant- and animal-based foods, yet only about 30% of the foods you eat contain significant amounts. Lectins are thought to have evolved as a natural defense in plants, essentially as a toxin that deters animals from eating them. In fact, lectins are highly resistant to your body’s digestive enzymes and can easily pass through your stomach unchanged.
Animal studies suggest that certain lectins can reduce the body’s ability to absorb nutrients. How they work remains a mystery, though animal research shows certain types of lectins bind to cells on the gut wall. This allows them to communicate with the cells, triggering a potential adverse response such as damaging the gut wall through an inflammatory response. This causes irritation that can result in symptoms like diarrhea and vomiting. It can also prevent the gut from absorbing nutrients properly.
You may have heard lectins described as antinutrients. Antinutrients are plant compounds that reduce the body’s ability to absorb essential nutrients. They are not a major concern for most people, but may become a problem during periods of malnutrition, or among people who base their diets almost solely on grains and legumes. However, antinutrients aren’t always “bad.” Under some circumstances, antinutrients like phytate and tannins may have some beneficial health effects as well.
The most widely studied antinutrients include:
Phytate (phytic acid): Mainly found in seeds, grains and legumes, phytate reduces the absorption of minerals from a meal. These include iron, zinc, magnesium and calcium.
Tannins: A class of antioxidant polyphenols that may impair the digestion of various nutrients.
Lectins: Found in all food plants, especially in seeds, legumes and grains. Some lectins may be harmful in high amounts, and interfere with the absorption of nutrients.
Protease inhibitors: Widely distributed among plants, especially in seeds, grains and legumes. They interfere with protein digestion by inhibiting digestive enzymes.
Calcium oxalate: The primary form of calcium in many vegetables, such as spinach. The calcium bound to oxalate is poorly absorbed.
The highest concentrations of lectins are found in healthy foods like legumes, grains, potatoes, and nightshade vegetables. Luckily, there are several ways to reduce the lectin content of these healthy foods to make them safe to eat. Research shows that by cooking, sprouting, or fermenting foods that are high in lectins, you can easily reduce their lectin content to negligible amounts.
Some foods high in lectins include legumes like red kidney beans, soybeans, wheat, peanuts, and nightshade such as tomatoes, peppers and eggplant. It is important to note that legumes are among the richest sources of plant-based protein and are also a great source of carbs that are low on the glycemic index (GI). This means that they release their sugars more slowly into your blood, causing a gradual rise in blood sugar rather than a sharp spike. What’s more, they’re also high in resistant starch and insoluble fiber, which can aid weight loss and improve general gut health. They also contain many vital vitamins and minerals. However, raw kidney beans also contain high levels of a lectin called phytohaemagglutinin. If you eat them raw or undercooked, they can cause extreme nausea, vomiting, and diarrhea. On the other hand, fermentation and sprouting are both 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%. Fermented soybean products include soy sauce, miso, and tempeh.
Tomatoes are full of vitamins, minerals, and antioxidants, such as lycopene. Similarly potatoes are also a good source of some vitamins and minerals. They contain high levels of potassium, which has been shown to decrease the risk of heart disease. They are also a good source of vitamin C and folate.
As mentioned above, only about a third of the foods you eat likely contain a significant amount of lectins. These lectins are often eliminated by preparation processes like cooking, sprouting, and fermentation. These processes make the foods safe by removing much of the lectins, so they will not cause adverse effects in most people. Nevertheless, nightshade vegetables may cause problems for some people. If you’re one of them, you may benefit from limiting your intake.
Though some dietary lectins are toxic in large doses, people generally don’t eat that much. Most of these lectin-containing foods are high in vitamins, minerals, fiber, antioxidants, and numerous beneficial compounds. The benefits of these healthy nutrients may outweigh the negative effects of trace amounts of lectins.
Ultimately, listen to your body and perhaps eliminate these foods from your diet and see how you feel. After 6 weeks you can begin to introduce those foods back into your diet and listen to what your body tells you.
And remember: soak, sprout, boil, ferment if you want the goodness of these foods without the lectins.