Lectin-free diet

Plants cannot move from place to place. They need protection from predators and to protect themselves, they produce certain toxic chemical substances such as lectins.
Lectins are carbohydrate-binding proteins and are abundant in nature.  
They are present in both plants and animals. Lectins present in plants function as primary defence as they protect plants from predators like human beings by attacking their intestine and immune systems.
Not all, but some lectins are powerful toxins such as ricin found in castor plant and wheat germ lectin. Wheat germ lectin shows its effect on the immune system by increasing inflammation.

Lectins were first described by Peter Hermann Stillmark, Baltic German Microbiologist, in his doctoral thesis presented in 1888 to the University of Dorpat. He isolated an extremely toxic hemagglutinin lectin called ricin from seeds of the castor plant.

Dietary Lectins present in raw food sources cannot be digested. They cause the sticking of cells and molecules to each other and this stickiness will make them attach to the intestinal wall.
Large amounts of dietary lectins increase gut permeability by attaching to the intestinal wall, causing bacteria and other toxins to cross the gut barrier easily.  This causes pain in the abdomen, nausea, vomiting and diarrhoea.
Lectins are also considered as anti-nutrients because they block the absorption of some nutrients.

Lectins, found in cucumbers, tomatoes, whole grains, soy, grains, peppers, sprouted grains and some dairy products are responsible for Alzheimer’s disease and dementia.
They also cause change in immune system and blood levels and also block insulin receptors.
Lectin containing foods like tomatoes, potatoes and cucumbers should not be taken in excess as our bodies cannot   tolerate high amounts of lectin.

Lectin-free diet

The lectin-free diet involves reducing lectin intake or complete elimination of lectin containing food from the diet.
In a lectin free diet, Foods to eat are all seafood, meat, chicken/turkey (all fowl), eggs, cheese, A2 milk
vegetables like cruciferous vegetables, such as brussels sprouts, broccoli, cabbage, cauliflower, collard greens and kale, cooked sweet potatoes, garlic, onion, pumpkin, carrots, leafy green vegetables, mushrooms, olives, asparagus, lemon cucumbers, celery
fruits like blueberries, avocado, pineapple, oranges, golden berries, papaya, mulberries, cherries, apples and mango

Foods to avoid are nightshade vegetables, such as eggplant, peppers, potatoes, and tomatoes
legumes, such as beans, peas, lentils, and peanuts, squash

It is practically impossible to avoid lectin- foods from our diet completely.

The processes like cooking the food sources at high temperature, Soaking and boiling, fermentation, sprouting, peeling, deseeding, pressure cooking will decrease the lectin activity and make them safe to eat.

Lectins also have some useful and desirable effects. Some lectins (such as CLEC11A) are beneficial, as they help in bone growth, control protein levels in the blood and also play an important role in the immune system by eliminating pathogens involved in the innate immunity.
When they are present in small amounts, they help the useful bacteria present in the gut. Lectins are also useful as they help in cancer diagnosis.
They also have the capacity to slow down the rate of multiplication of cancer cells. They are antimicrobial and also support the immune system.

Researchers are working on lectins to find out possible treatments for bacterial, viral and fungal infections.

A lectin-free diet may be difficult for vegetarians or vegans to follow, since legumes, nuts, seeds, and whole grains provide plant-based lectin.
They are advised to take lectin containing properly cooked plant foods along with fibre rich plant foods.
Antioxidants of whole grains help to compensate for the harmful effects of lectin.