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Lectins are carbohydrate-binding proteins that are found in most plants, particularly seeds and tubers such as cereal crops, potatoes, and beans (legumes).  Traditionally, they have been used as histology and blood transfusion reagents but lectins may be toxic, inflammatory, resistant to cooking or digestive enzymes, and are found in much of our foods.  So how safe are lectins, really?

What are Lectins and What Damage can they Cause?

Lectins are proteins that do not break down easily, and they are resistant to both stomach acid and digestive enzymes.  Lectins may bind to the wall of the gut and damage the gut lining.  They can cause changes in the function of the gut which may be related to diseases such as colitis, Crohn’s disease, Coeliac-Sprue, and IBS.  Because of the damage that lectins do to the gut, other proteins may be able to cross into the body undigested and cause allergic reactions within the body.

As lectins can cross into the body through a damaged gut wall, they can bind to cell membranes in arteries and vessels, organs, and glands. This binding can create reactions which lead to auto-immune disorders or degenerative diseases.  Different lectins are associated with different diseases.  For example, dairy-based lectins are associated with juvenile onset type one diabetes.

Some other diseases that are thought to be associated with lectins include:

  • insulin dependent diabetes
  • rheumatoid arthritis
  • IgA nephropathy
  • peptic ulcers

It can be helpful to think of lectin as a type of protein that contains a key that fits a certain lock. The lock is a specific carbohydrate.  If the lectin has the right key comes into contact with the right lock or carbohydrate, the lock is opened, damaging the cell membrane, and thus damaging the cell.  The lectins, however, can be inactivated by specific carbohydrates known as mono and oligosaccharides, which bind the key and stop it from fitting the lock.  It is best not to rely on these carbohydrates completely, though, as the safest path is to avoid all known toxic lectins.

How Do We Become Sensitive to Lectins?

Lectin sensitivity can occur for a variety of reasons.  For starters, we did not evolve to eat the types of food that contain lectins and so the immune system may not be able to handle it.  A certain form of barrier protection in the body, SIgA barrier protection, may fail, for genetic or environmental reasons.  The body may contract a bacterial or viral infection that damages the cells, making them more prone to lectin antibody reactions.  Another reason is by using non-steroidal anti-inflammatories (NSAIDs) or other drugs which increase gut permeability and allow lectins to enter the body.

What Foods Contain Problematic Lectins?

Lectins are found in foods, and the amount of lectins contained in the food depends on the type of plant, how it was processed, and the species.  The main foods that may contain toxic lectins include:

  • grains such as wheat and wheat germ but also quinoa, rice, oats, buckwheat, rye, barley, millet, and corn
  • legumes
  • dairy foods
  • the nightshade family e.g. potato, tomato, eggplant, cucumber and capsicum

It is interesting to note that all of these foods have been found to be involved in or cause food allergies or intolerances.  The lectins in foods may be inactivated by soaking, sprouting, cooking, or fermenting.  Soaking legumes overnight and rinsing them well does seem to remove or inactivate many of the lectins present.  Heating may remove lectins in some foods, but not all.  Be aware, however, that of the stated methods, there is little research to prove that they completely remove lectins from foods.

What Can I Do If I’m Lectin Sensitive or Intolerant?

If you are intolerant to lectin, this means that you are not able to stop lectin from binding to the cells in your body.  The lectins therefore create immune responses that damage the cell to which the lectins are attached and potentially surrounding cells.

An elimination diet will need to be undertaken to find out if you are lectin sensitive.  This is where you remove all suspect food groups from your diet for seven days.  On the eighth day, slowly begin reintroducing the eliminated foods.  It is best to only test one food group at a time.  If you notice anything suspicious, such as changes in energy, appetite, bowel function, mood, sleep, or digestion, there is a good chance that you are sensitive to the food.  Once you have identified the suspect food group, it is just a matter of eliminating it from your diet as much as possible.  After twelve months, you can try re-introducing the food into your diet once more.  If you do not react, it is likely that is an environmental intolerance brought on by infection or medication.  If you do react, however, it is likely that it is a genetic intolerance and you will never be able to safely consume the food.

The Good Side of Lectins

The news is not all bad when it comes to lectins.  There have been studies that show that lectins are able to make abnormal and malignant cells stick together, as well as stop them from functioning.  This has important overtones when it comes to types of cancer.  Soy protein in low concentration has this effect on cancer cells, while leaving normal cells alone in blood types A and AB.  Peanut lectins are shown to fight breast cancer cells in blood types A and AB.

Peanut lectins inhibit cancer cell growth and destroy cancer cells in blood types A and AB.  Soy bean lectins makes cancer cells stick together and also destroys them in blood types A and AB.  Fava bean lectins promote cell differentiation in all blood types. Amaranth lectins inhibit cancer growth in blood types A and AB.  Domestic mushrooms promote cell differentiation in all blood types and jackfruit lectins stick together T antigens in all blood types.


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