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Beyond Gluten: The Impact of Lectins on Health


Lectins are a type of protein found mainly in plants. They are defined as proteins that bind to carbohydrates, but more generally, lectins are an important class of plant defense substances. To defend against predators such as insects and animals, the amount of lectins is highest in the plant parts most important for plant reproduction: the seeds (nuts, grains, corn, beans, and other legumes). High amounts of lectins are also found in immature fruit.


Gluten is the best-known (or most infamous) lectin, but many others exist. Another example is phytohemagglutinin, which is found in large amounts in raw red beans. Among other things, phytohemagglutinin causes red blood cells to clump together. Because of this, eating even small amounts of raw or undercooked red beans can cause severe poisoning reactions, nausea, vomiting, stomach upset, and diarrhea. Milder side effects include flatulence.


The amount of lectins found in the blood after eating a lectin-rich food, such as peanuts, can vary from person to person and is related to whether or not someone has leaky gut syndrome (a hyperpermeability of the intestines).


Image from my book: FOOD FOR HEALTH


This permeability of the intestines allows toxins such as lectins and other particles to enter the bloodstream.


Lectins can also cause leaky gut syndrome directly by binding to the epithelial cells of the intestinal mucosa.


However, there are many causes of leaky gut syndrome, including vitamin A deficiency, vitamin D deficiency, stress, parasites, fungi (candida overgrowth), infections, antibiotics, anti-inflammatory medications, insufficient stomach acid/proton pump inhibitors, alcohol consumption, emulsifiers, titanium dioxide particles (often found in candy and chewing gum), pesticides, particulate matter (what we breathe in has also been shown to affect our gut), and chemicals in plastics (like PBA).


So what happens when lectins enter your bloodstream where they don’t belong?


1. Activation of the immune system


Our immune system fights off lectins and removes them from our bloodstream. Besides the general symptoms associated with this, mainly inflammation and joint pain, the connection with weight loss is fascinating.


Your adipose tissue is an essential part of your immune system. More specifically, it is involved in regulating the immune system through hormones called adipokines, which control immune cell activity. This leads to an interesting relationship between fat accumulation and low-grade systemic inflammation.


Image from my book: FOOD FOR HEALTH


But is the relationship purely one-sided? Does fat accumulation cause inflammation, or can such inflammation also slow weight loss by «holding onto» adipose tissue?


Indeed, it has already been shown that chronic inflammation can lead to fat accumulation, particularly ectopic fat accumulation, i.e., fat accumulation in and around organs (visceral fat).


2. Lectins can stimulate the insulin receptor of cells.


You might have heard about insulin being a fat-storage hormone. In the following figure, you see a graph comparing the fat storage of cells in a glucose solution. On the x-axis (horizontal) is time, and on the y-axis (vertical) is the conversion of glucose to fat in fat cells.


Image from https://doi.org/10.1210/endo-113-6-1921 , Y. Shechter: Bound lectins that mimic insulin produce persistent insulin-like activities.


Here you can see how strongly fat storage was stimulated by insulin, by a combination of insulin and the lectin wheat germ agglutinin, and by wheat germ agglutinin alone. It is noticeable that the combination of insulin with lectins, as well as the effect of the lectins alone, is much greater than the effect of insulin alone.


Another critical point is that lectins can stimulate the insulin receptor much longer than insulin. Lectins, unlike insulin, can cause permanent binding to the insulin receptor and permanent lipogenesis (fat buildup). This has been tested and demonstrated for several lectins: wheat germ agglutinin, wax bean agglutinin, and concanavalin A. These types of lectins that can bind to the insulin receptor are called insulinomimetic lectins - in other words, they mimic insulin.


Image from my book: FOOD FOR HEALTH


3. Lectins can inhibit the binding of leptin to leptin receptors, which effectively corresponds to leptin resistance.


Leptin is a hormone secreted primarily by fat cells into the bloodstream and is commonly known as the satiety hormone. It regulates food intake and energy expenditure by activating a receptor in the brain's hypothalamus. But leptin has a variety of functions, including regulating stem cells that can develop into all types of blood cells, affecting wound healing, forming new blood vessels, and regulating immune and inflammatory responses.


Lectins such as concanavalin A or wheat germ agglutinin have been found to inhibit leptin binding to the leptin receptor, leading to leptin resistance. Although leptin resistance can have many causes and is a complex issue, it is interesting to keep this point in mind and monitor your hunger response to certain foods. It is also worth noting that a delayed hunger response, such as the next day, is possible.


Image from my book: FOOD FOR HEALTH


Last but not least, a picture of two mice that differ only in their leptin resistance.


Image from https://doi.org/10.1210/ endo-113-6-1921, Y. Shechter: Bound lectins that mimic insulin produce persistent insulin-like activities.


4. Lectins can trigger autoimmune diseases through molecular mimicry (imitation).


But first things first: what are autoimmune diseases?

Autoimmune diseases can have very different clinical pictures. However, they are all characterized by our immune system attacking our own tissues. One of the characteristic features of autoimmune diseases are the so-called autoantibodies.


To understand this, we need to look at two main components: Antigens and antibodies.


Antigens are molecules that can trigger an immune response. Each antigen has certain surface features that lead to specific responses.


Antibodies (immunoglobulins) are Y-shaped proteins produced by the B cells of the immune system in response to contact with antigens. Antibodies are specific for an antigen and act like a lock-and-key binding mechanism. This binding helps remove antigens from the body by either neutralizing them directly or «tagging» them so that other parts of the immune system can become active and eventually destroy the pathogen.



So when our immune system produces antibodies for a particular pathogen, its affinity for that pathogen is high. However, when these antibodies encounter healthy cells (which have their own specific antigens), they hopefully have no affinity for those cells.


So how can an autoimmune problem arise?

One important mechanism is what is known as molecular mimicry, which is the similarity between antigens on pathogens and antigens on our own cells. This similarity can lead to antibodies that can also bind to healthy cells, which in turn can lead to the destruction of healthy tissue. Such antibodies are called autoantibodies and are among the most important factors in diagnosing autoimmune diseases.


We have already discussed leaky gut syndrome and how lectins such as gluten (among many other factors) can directly lead to the characteristic increased permeability of the gut.


Increased gut permeability, in turn, can allow lectins and other pathogens to enter the bloodstream. When these factors combine with a genetic predisposition to autoimmune disease, the path to it is paved.


Image from my book: FOOD FOR HEALTH


Lectins are not the only trigger of autoimmune diseases. Another important contributing factor through molecular mimicry is cell wall fragments from certain bacteria.


The link between a hyperpermeable gut and autoimmune diseases is further illustrated by the strong association between the following conditions and inflammatory bowel disease:

  • Rheumatoid arthritis

  • Lupus

  • Ankylosing spondylitis

  • Psoriasis (psoriasis)

  • Atopic eczema (neurodermatitis, atopic dermatitis)

  • Asthma

  • Diabetes type I

  • Multiple sclerosis


Image from my book: FOOD FOR HEALTH


In next week’s blog post, we will discuss the best preparations of lectin-rich foods, which can reduce the lectin content significantly, including a comprehensive food table. Stay tuned!

 

Find more nutrition facts and tips in my book FOOD FOR HEALTH, available now in the shop and on all Amazon Marketplaces!





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