Lectins. Never heard of them? Heard too much about them? Either way, you are probably not alone. Lectins are obscure, but they have also made headlines lately due to a recent book release. There are a lot of differing points of view on lectins: some warn against their toxic effects, while others tout their health benefits. My goal is to provide information that I have found on lectins and to summarize a prudent approach to consuming them.

What are they?

Lectins are a class of proteins that can bind to carbohydrates. They are found in raw legumes, raw whole grains, raw seeds and nuts, and many fruits and vegetables. It is important to emphasize that some of these are toxic, while some are unlikely to be so and may even provide some health benefits, such as protection against cancer. They are a plant’s natural defense mechanism against pathogenic microorganisms and pests — including humans — who eat them. Many seeds, for example, are resistant to digestion and are designed by nature to pass unaltered through an animal’s digestive system, thereby allowing the seed to be spread in the environment and hopefully germinate later on.

Toxic Lectins

There are two main classes of the toxic lectins: prolamins and agglutinins. Our digestive tracts are not suited to breaking them down. They also contain compounds that inhibit protein-digesting enzymes. Toxic lectins can also damage the intestinal lining, leading to intestinal permeability — or leaky gut — as well as inflammation, and can contribute to autoimmune disease in susceptible individuals.

Where are they found?

The two food classes with the highest toxic-lectin content include raw whole grains and legumes (beans, peas and lentils, with the exclusion of beans with edible pods). Peanuts, soybeans, broad beans such as favas and limas, and kidney beans are among the highest toxic lectin–containing legumes. Just five raw kidney beans can provoke a reaction similar to food poisoning. Cooking greatly reduces lectin content, but does not completely eradicate it. (See more below.) Ricin, a lectin extracted from the castor bean, is an extreme example of a toxic lectin and is a potent poison.

Wheat Germ Agglutinin (WGA) is another example of a toxic lectin and probably the most well studied grain lectin. Again, it interacts with the lining of the intestine, potentially increasing intestinal permeability. It can also stimulate the immune system and lead to inflammation. Gliadin, a type of gluten protein in wheat, is another example with similar effects.

Nightshades

Nightshades are plants in the Solanaceae botanical family. It includes tomatoes, tomatillos, potatoes, peppers, eggplants, ground cherries, and goji berries, among others. Many people have bad reactions to these, though it is not known if it is a genetic incompatibility to the solanine or the lectins they contain. Ripeness also plays a factor (see below).

Foods with fewer lectins

There are several foods that naturally contain fewer lectins. Most fruits and vegetables, aside from nightshades, fall into this category. Eating fully vine-ripened fruits and vegetables will additionally ensure fewer lectins; lectins in immature plants prevent them from being eaten by pests before their seeds are mature. Lentils and adzuki beans contain fewer lectins, perhaps partially because they are smaller and take less time to cook. Buckwheat and white rice are two grains low in lectin.

Food Processing

Our ancestors knew what they were doing when they soaked, sprouted, fermented, and cooked their grains and legumes for long periods of time. These processes can all drastically reduce the lectin content — in addition to other antinutrients — but may not eradicate them completely. Cooking legumes with certain spices such as curry spices and ginger, or with the addition of seaweed, can also help. A true sourdough bread is a good example of grain fermentation; this process allows for the partial breakdown of the grains and lectins by microbial action, which is why it is healthier than fast, yeast-leavened bread.

Should you eradicate lectins from your diet? First, there are many healthy foods such as fruits and vegetables that contain lectins that will not harm health. In fact, there is some research that suggests lectins may even offer a protective benefit in terms of cancer, especially colon cancer. In addition, modest, occasional consumption of toxic lectins will probably not have a significant negative effect on health, especially if you prepare your foods properly, and otherwise eat a nutrient-dense diet. However, eating large quantities of toxic lectins regularly, especially foods with the highest concentrations, may very well have a negative effect. Those who are most susceptible include vegetarians or vegans who rely heavily on legumes, seeds and grains; those with autoimmune disease, a growing percentage of the population; and those who often experience digestive distress. In these cases, you may wish to do your own N=1 experiment by doing a trial elimination of these foods and see how you feel without them.

The information provided in this article is intended for general use only and is not to be used in place of medical advice from a licensed health professional.