Lectins are carbohydrate binding proteins present in the majority of plants, particularly in seeds and tubers like potatoes, cereals, and beans.
The exact role of lectins in plants is unclear, although they can serve as powerful insecticides and are important for seed survival. For example, castor beans contain so much lectin that they are toxic to most organisms. In fact, ricin, which is found in castor beans, is so toxic that it’s used as a weapon in biochemical warfare.
Lectins’ side effects on humans
Consuming these compounds can cause digestive distress in humans. In addition, some lectins, such as the phytohaemagglutinins (particularly found in certain legumes), can be downright poisonous.
They also have other negative effects, such as:
- cell metabolism disorders;
- they induce mitosis (the division of the nucleus) and affects the cell membrane in regard to permeability and transport to proteins;
- they agglutinate to the most mammalian red blood cell types;
- they can raise the risk of autoimmune disease. An autoimmune disease develops when your immune system, which defends your body against physical disease, decides your healthy cells are foreign;
- they can interact with the immunoglobulin function, which is an important component of the immune system.
Signs that you might be experiencing problems from lectins in your diet:
- changes in bowel habits;
- severe flatulence and bloating after meals;
- painful and swollen joints;
- hormonal fluctuations;
- achy muscles and joints;
- tiredness and fatigue;
- allergic response. You may notice sniffling or sinus congestion, watery eyes, tightness in the throat, and itchy mouth, skin, or tongue;
- skin eruptions;
- white kidney bean hemagglutinins can cause vomiting, acute nausea, and diarrhea.
It is easy to get rid of these compounds from the food you ingest, with the right preparation methods. Cooking, as well as soaking or sprouting, the beans is a must. Soaking beans overnight not only cuts down on cooking time but also helps the beans cook evenly without splitting.
A 2005 article published in “Critical Reviews in Food Science and Nutrition” concluded that these substances may have some anti-cancer potential via changes to the immune system and minimizing the growth of tumors, although more studies are still needed to prove these benefits.
They also play other important roles in the body. For instance, they activate the complement immune system, which helps fight pathogens.
Here is a list of foods high in lectins:
Grain-fed milk is higher in these compounds than grass-fed milk. Also, dairy lectins have been implicated in juvenile-onset type I diabetes. This type of diabetes is one of the most common chronic childhood conditions and represents about 10% of all cases of diabetes.
Symptoms of type 1 diabetes can include:
- unexplained weight loss;
- increased urination and thirst;
- blurred vision;
- increased hunger.
Interesting note – dairy products contain an immunoglobulin which helps neutralize lectins. Unfortunately, this antibody is destroyed during pasteurization (a process in which dairy products are treated with mild heat, to extend shelf life and eliminate pathogens).
Many genetically modified organisms foods have these compounds spliced into them as part of their engineering process, and the resistance to heat and toxicity is relatively unknown and untested.
Beans and pulses
A pulse is an edible seed that grows in a pod. Pulses include all peas, beans, and lentils, and all contain lectins. The list includes:
- chickpeas ( also known as garbanzo beans);
- red, green, yellow and brown lentils;
- black-eyed and garden peas;
- kidney beans, runner beans, broad beans (fava beans), castor bean, butter beans (Lima beans), cannellini beans, haricots, pinto beans, flageolet beans, and borlotti beans.
Tip – to decrease their lectins content )over 95 percent), soak and pressure-cook legumes.
All types of potatoes (including sweet potatoes), zucchini, rhubarb, asparagus, carrots, beets, mushrooms, turnips, and radishes.
Tomatoes, pumpkin, cucumbers, sweet peppers, eggplant, oranges, grapefruit, lemons, raspberries, blackberries, strawberries, pomegranate, cherries, grapes, watermelon, quinces, apples, plums, banana, papaya, and currants.
Tip – lectins are concentrated in the seeds and peels, therefore, to reduce the lectin content of peppers and tomatoes you can peel and de-seed them.
Barley, corn, oats, rice (the majority of the lectins in rice are not in the part that gets eaten), rye, wheat, quinoa, buckwheat, millet, and corn.
Tip – to reduce their lectins content, sprout or soak these grains before cooking.
Seeds and nuts
Hazelnuts, walnuts, peanuts, pecans, sunflower seeds, hemp seeds, and sesame seeds.
The majority of these lectin-containing foods are high in minerals, vitamins, dietary fiber, antioxidants, and many other beneficial plant compounds. Therefore, the health benefits of these healthy foods far outweigh the side effects of trace amounts of lectins.