Lectins are plant proteins that bind to carbohydrates. In nature, plants use lectins as a defense against being eaten. When they bind to carbohydrates, it makes them harder for the human gut to digest. Lectins are in most plants, but especially high in beans, lentils, and some vegetables. Even though these foods a part of a healthy diet, it’s helpful to understand how lectins can affect digestion.
Are Lectins Harmful?
There’s good news, and there’s bad news.
The bad news is that lectins in their active state can cause some digestive problems, like nausea, vomiting, upset stomach, and diarrhea. In animal studies, active lectin blocked the absorption of iron, phosphorus, zinc, and calcium – the very nutrients that many lectin-containing foods are rich in. This is why lectins are sometimes called “anti-nutrients.”
It’s sounding grim, but there is good news.
The good news is the active lectins are very rarely eaten by humans. Foods that are highest in active lectins are raw legumes, and the cooking required to eat them ends up denaturing most lectins. (Denaturing is when the structure of a protein is modified, usually by heat or acidity). The human body has enzymes that helps break down the remaining lectins that make it past the cooking stage. Interestingly, the lectins found in tomatoes and bell peppers do not cause digestive stress in most.
Even better, research shows that people who eat legumes, whole grains and nuts have a lower risk for heart disease and diabetes and have an easier time maintaining a healthy weight.
How to Denature Lectins
- Soak dried beans overnight before cooking. Lectins are water-soluble and can be washed off. Canned beans are already cooked, and packed in liquid, so they are already low in lectins.
- Cook your legumes on high heat to reduce the amount of lectins. It’s important to note that cooking legumes in a slow cooker on low heat does not remove all the lectins.
- If you sprout your beans and grains, remove the outer hull of beans and wheat grains.
The Bottom Line on Lectins
Legumes, whole grains foods, nuts, and other foods that contain lectin are a part of a healthy, balanced diet, as long as these foods are cooked thoroughly. Current research does not support any need to exclude foods with lectins from your diet.
One exception are those with irritable bowel syndrome or multiple sclerosis. People with these conditions may be more sensitive to lectins and benefit from a diet lower in lectins.
Suzanne Watkins is a dietitian at Samaritan Albany General Hospital. If you have questions about nutrition, ask your primary care clinician for a referral for nutrition counseling.