Are Lectins Bad For You? 5 Foods To Avoid (2024)

Lectins are proteins that bind to carbohydrates, says Alex Foxman, M.D., a board-certified internist and the medical director of Achieve Health and Weight Loss. They are found in most plants, but some foods like beans and tomatoes have higher amounts of lectins than others, he says.

“Lectins have various functions in plants, such as defense against pests and pathogens, cell recognition and communication and seed germination,” says Dr. Foxman.

In humans, lectins resist digestion and may affect the lining of the intestines and nutrient absorption, says Kim Kulp, a registered dietician nutritionist, gut health nutrition expert and owner of the Gut Health Connection in California.

“Some lectins, such as phytohaemagglutinin (present in raw or undercooked kidney beans), can cause severe symptoms such as nausea, vomiting, diarrhea and red blood cell clumping,” says Dr. Foxman.

Eating foods with a high amount of lectins is rare, says Brittany Werner, a registered dietitian nutritionist at Working Against Gravity, a nutrition coaching program. Lectins are most potent in their raw state, such kidney beans and potatoes, and high-lectin foods aren’t typically eaten raw, she explains.

Fortunately, it’s easy to avoid adverse effects from lectins, says Pratima Dibba, M.D., a board-certified gastroenterologist at Medical Offices of Manhattan in New York City. For example, boiling, steaming or soaking lectin-containing foods like whole grains minimizes their lectin content, making them unlikely to cause harm, she says.

In fact, lectin-containing foods have many health benefits, says Werner. For example, some lectins are antioxidants, which protect cells from damage caused by unstable molecules within cells, otherwise known as free radicals, she says.

Lectin-containing foods like beans, whole grains and nuts are also associated with lower rates of Type 2 diabetes and cardiovascular disease, says Werner. Many lectin-containing foods like tomatoes and potatoes are also rich sources of B vitamins, protein, fiber, minerals and healthy fats, says Werner.

When prepared properly, the health benefits of these foods surpass their potential harm, explains Werner.

Should You Avoid Lectins?

“Lectins aren’t our enemy,” says Maria Tointon, a registered dietitian nutritionist based in Honolulu, Hawaii, and the owner of Veg Out With Maria. Before eliminating lectin-containing foods, Tointon suggests considering their overall health benefits. For example, legumes and whole grains reduce the risk of coronary heart disease, cancer and inflammation.

“There’s no conclusive evidence that avoiding lectins benefits everyone,” says Dr. Foxman. However, individuals with digestive issues, food allergies or intolerances or autoimmune conditions may consider limiting lectins as these foods can aggravate the digestive tract, he adds.

“Most lectins can be deactivated or reduced by soaking, sprouting, fermenting or cooking foods with water and heat,” says Dr. Foxman. Instead of avoiding all foods with lectins, he advises preparing them properly before consumption.

These foods contain high amounts of lectins, making it especially important to not eat them raw.

Uncooked beans

“Never eat uncooked or undercooked beans,” says Tointon. According to the U.S. Food and Drug Administration (FDA), raw beans like red kidney beans and soybeans contain high levels of phytohaemagglutinin (PHA), which can cause nausea, diarrhea and severe vomiting. While canned beans are safe, raw beans should be soaked for five hours, then rinsed and boiled for 30 minutes before consuming to avoid these adverse effects.

Peanuts

“Peanuts contain peanut agglutinin (PNA), [a lectin] that can cross the intestinal barrier and enter the bloodstream,” says Dr. Foxman. He adds that PNA may trigger allergic reactions and affect blood vessel and platelet function. Boiling, roasting or microwaving peanuts destroys 98% to 100% of their lectin content^[1]Lectins in Peanuts and Other Foods. The Peanut Institute. Accessed 10/14/2023. .

Cashews

“Cashews contain anacardic acid and cardol, which can cause skin irritation and allergic reactions in some people,” says Dr. Foxman. They also contain phytic acid, an anti-nutrient (a compound that interferes with the absorption of nutrients) that may affect the absorption of minerals like calcium, iron and zinc. “Cashews should be soaked for at least six hours and roasted or boiled before eating,” he adds.

Whole Grains

Whole grains, especially wheat, contain high amounts of lectins in their raw form. They also contain phytic acid, which can reduce the bioavailability of some nutrients, says Dr. Foxman. Soaking, sprouting or cooking (by boiling or pressure-cooking) whole grains before eating them minimizes their lectin content, he says.

Nightshade Vegetables

Eggplants, tomatoes, peppers and white potatoes are vegetables categorized as nightshades that are high in lectins. While some research indicates that nightshade vegetables may worsen symptoms in individuals with gastrointestinal conditions such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), this is likely due to their glycoalkaloid content, a naturally-occurring plant compound that can have negative effects on human health.

To avoid these effects, avoid eating nightshades raw and peel potatoes before cooking them.

There’s little evidence that lectin-containing foods should be eliminated from the diet, says Dr. Dibba. What’s more, the established health benefits of lectin-containing foods outweigh their potential risks, she adds.

Individuals with no known food intolerance, allergy or sensitivity don’t need to avoid lectins, says Tointon. “Just avoid eating huge amounts of a single food and include a variety of plant foods in your diet,” she adds.

If you’re experiencing bothersome digestive symptoms, Tointen recommends working with a registered dietitian to evaluate your diet as a whole and determine potential underlying conditions.