Lectin proteins can be found in many foods, especially cereals, beans, seeds, nuts, fish and shellfish. Dairy foods and plants in the nightshade family contain lectins, as well. Plants use lectins, a low-grade toxin, to kill off fungus and small insects and ward off larger predators. But while lectins can help a plant survive, they can cause you some distress -- ranging from rash and joint pain to vomiting, abdominal cramping and diarrhea -- especially if you have a lectin allergy or sensitivity. Sometimes the heat from cooking can destroy the lectins, but in some cases, it cannot.
Grain Lectins
Whole-grain foods are nutritious but also tend to have more lectins than their refined counterparts. Because whole-grain breads and cereals are more widely consumed today than they were a decade ago, exposure to lectins in the diet is increasing. You could eat refined baked goods, but that poses its own set of problems. Another alternative is soaking, cooking, fermenting and sprouting grains. These can decrease the lectin content in foods. The longer sprouts grow, the less lectin they have.
Legume Lectins
Legumes, plants expressing fruits in pods, contain high amounts of lectins. Peas, beans, soybeans, peanuts and lentils are legumes. Lectins in legumes can be especially problematic. Concanavalin A, a lectin in uncooked jack beans, can bind to your red-blood cells, causing them to clump together. It can also bind to cells in your intestine, disrupting nutrient absorption. Soaking, sprouting or cooking legumes can reduce the lectin content. Raw kidney beans contain up to 70,000 lectin units, while fully cooked beans may have only 400 units.
Nightshade Family Lectins
Plants in the nightshade family contain lectins that tend to irritate people with autoimmune conditions and inflammatory arthritis. Potatoes, tomatoes, peppers, eggplants and certain spices in a Western diet have high levels of lectins. Potato starch, a hidden source of lectin, is commonly used as a thickening agent and as a filler in foods and prescription medications. Spices containing lectins include paprika, cayenne and chipotle. Black and white peppers do not contain lectins.
Other Food Lectins
Other foods contain lectins in lower quantities. Among them are fruits, including blackberries, cherries and bananas, and vegetables, including carrots, zucchini and asparagus. Among fish with lower quantities of lectins are halibut and tuna. A survey on foods published in 1980 issue of "The American Journal of Clinical Nutrition" concluded that about 30 percent of foods commonly eaten have lectins.
References
- "Townsend Letter for Doctors;" Dietary Lectins--Blood Types & Food Allergies; Laura Power; June 1991
- The Lectin Report; Krispin Sullivan, May 2011
- Balanced Bites Nutrition and Wellness; Nightshades; Diane Sanfilippo
- Precision Nutrition; All About Lectins; Ryan Andrews; August 2009
- "Pakistan Journal of Nutrition;" Dietary Lectins as Disease Causing Toxicants; Rabia Hamid, Akbar Masood; 2009
- Cornell University; Plants Poisonous to Livestock--Plant Lectins; June 2011
