The Truth About Lectins—Why Beans Have Gotten a Bad Rap

Photo by David McLain, The Blue Zones Kitchen


The longest-lived people in the world eat a mainly plant-based diet that, at its foundation, is centered on beans, legumes, greens, nuts, whole grains, and fruits. In the blue zones, they eat seasonally, they cook at home, and they often celebrate and dine with friends around the table. Hailing from all parts of the globe, the healthiest people in the world share a common pantry staple—beans

Some recent fad diets and media headlines have made beans a controversial (and often eliminated) food due to their high lectin content and the claim that lectins cause inflammation and indigestion. So, what are lectins and are they safe to consume?

What are Lectins?

Lectins are proteins that are found in all plants that bind to carbohydrates. They are a protective measure that helps the plant thrive and survive in nature. The same characteristics that protect them in nature can lead to digestive discomfort if consumed by humans—but there’s a catch. Lectins are in ALL plants. Plants that we’ve been eating for thousands of years, like rice, wheat, potatoes, tomatoes, seeds, nuts, but the highest amounts are found in raw legumes (beans, lentils, soybeans, peas, and peanuts included) and whole grains. 

What about Lectin Poisoning?

If you eat raw beans, you will almost certainly have nausea, vomiting, upset stomachs, and diarrhea. At the very least, you’ll probably have uncomfortable bloating and gas. Some nonhuman studies have found that active lectins can interfere with the absorption of minerals like calcium, iron, phosphorus, and zinc. 

The good news is that cooking or soaking beans destroys active lectins. Dried beans have to be soaked and then boiled for at least ten minutes. But it takes about an hour to cook most beans so that they are edible. Dr. Greger of NutritionFacts notes, “Without presoaking, it takes 45 minutes in a pressure cooker to get rid of all lectins, but an hour to make kidney beans edible. So basically… cooking beans to the point where they are considered edible is more than sufficient to destroy virtually all lectin activity.” 

“…cooking beans to the point where they are considered edible is more than sufficient to destroy virtually all lectin activity.” 

What about canned beans? Dr. Greger says that’s even simpler: “Canned beans are cooked beans; the canning process is a cooking process.”

What the Research Says

If prepared correctly (i.e. soaked, canned, fully cooked), then lectin-containing foods are safe to consume. Studies show that boiling legumes, soybeans, and even kidney beans (which have extremely high lectin levels when raw), greatly reduces and often completely eliminates lectin activity. 

Lectins have health benefits, as well, and can act as antioxidants, protecting human cells from damage caused by free radicals. They are slow digesting and could prevent sharp rises in blood sugar. And in cases of population studies, and research from the blue zones, lectin-containing foods like whole grains and beans are associated with lower rates of cardiovascular disease, type 2 diabetes, and better health overall. Rich in B vitamins, protein, fiber, and minerals, the health benefits of lectin-containing foods outweigh any extremely small potential risks.

Dietary recommendations that promote the elimination of foods containing lectins are not supported by any major health organizations. Dr. Robert Eckel, a professor of medicine at the University of Colorado and a past president of the American Heart Association says, “This is against every dietary recommendation represented by the American Cancer Society, American Heart Association, American Diabetes Association and so on.” 

Preparing Plants for Your Plate 

It is rare to actually eat food with a high amount of active lectins, as many of the lectin-containing foods we eat (whole grains & beans) are never consumed raw, so there should be no fear when choosing to consume these centenarian favorites. Many lectin-containing foods are also high in fiber, which is essential for a healthy metabolism and good digestion, as well as a strong immune system.

Cooking with wet, high-heat methods like boiling, stewing, or soaking can deactivate most lectins. When it comes to the lectins in nuts and seeds, these are water-soluble and found on the outer surface so exposure to water removes them. If these foods have given you digestive discomfort in the past, look for “sprouted” varieties or soak your own nuts and seeds to deactivate the enzyme inhibitors and ease the digestive process. 

Canned beans are cooked and then packaged in liquid, making them low in lectins. Dried beans must be soaked for several hours and then boiled for several more to soften and cook completely, which effectively disables and deactivates the lectins. However, undercooked or raw beans simmered at low heat or cooked in a slow cooker will not remove all lectins because the heat is not high enough to help break down the enzymes. If beans have caused digestive issues in the past, try using canned beans for slow cooker recipes or soak and boil them before use in a slow cooker. 

In addition to proper cooking methods, consuming beans on a regular basis can actually improve your body’s ability to digest them. According to a study published in the BMC Medical Journal, people who ate beans every day for three weeks reported less intestinal gas and discomfort by the end of the study. Try working a small serving of beans into your daily diet and slowly increasing your portion sizes over time.

Avoiding lectins altogether would mean avoiding almost all plant foods, which would mean avoiding a majority of the foods that the longest-lived people in the world consumed every day of their lives as well as the foods shown to reduce risk of chronic diseases like heart disease and diabetes. Cooking properly, soaking, or buying canned beans protect you from digestive discomfort and potential harm. 



By Aislinn Kotifani, Blue Zones Communications Specialist

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