Are lectins harmful? 

The short answer is: it depends. It depends on the type of lectin, the individual and the dosage.

People with inflammatory, autoimmune or unexplained health problems should experiment with avoiding lectins from ALL grains, beans/legumes, nuts and potatoes/tubers (all varieties) for a period of 4 weeks. Staying away from most lectins or eliminating grains and eating legumes or nuts is not enough. Seeds can also be problematic for some, but this is less common.

A study was conducted on 800 people with autoimmune diseases who ate a diet that included avoiding grains, sprouted grains, pseudo-grains, beans and legumes, soy, peanuts, cashews, nightshades, melons and pumpkins, and non-South European cow's milk products (Casein A1), and grain- and/or bean-fed animals.

Most of these people had elevated TNF-alpha. The result after 6 months was a normalization of TNF-alpha in all patients who adhered to the diet.

The study concluded that elevated Adiponectin is a marker for lectin and gluten sensitivity, while TNF-alpha can be used as a marker for gluten/lectin exposure in sensitive individuals [1].

Anyone with flatulence or GI problems should realize that lectins are probably the main cause (stress is also important).

For healthy people without inflammation problems, I recommend soaking and sprouting grains, legumes and nuts as much as possible. Whole grains have more lectins than refined grains. Seeds are better sprouted, but less so.

People with anxiety disorders and/or gut problems should seriously consider a diet that restricts lectins, because lectins bind to serotonin receptors and transporters, disrupting their function [2, 3].

Lectins, in my opinion, are the main cause of autoimmune diseases.


What are lectins?

Lectins are proteins that bind to carbohydrates and are present in all life forms, including plants, humans, bacteria and viruses. Lectins are mainly concentrated in seeds and tubers (potatoes). Cereals, legumes and nuts are types of seeds and thus rich in lectins.


The benefits of some lectins

Lectins have a bad reputation, but they are not all alike. Some lectins are beneficial. In plants, lectins appear to be part of plants' natural defense mechanisms and important for seed survival.

Lectins have many essential functions in the body. For example, they activate the complementary immune system (part of the innate immune system), which helps fight pathogens [4]. For example, the lectin pathway helps us fight pneumonia [5].

Lectins are often antimicrobial [6, 7, 8]. For example, a lectin from bananas inhibits HIV-1 in test tubes [9].

Some herbs work through lectins. Bitter melon and garlic [10] are examples of herbs that contain lectins that can be beneficial.

Some herbs belong to the bean family and are therefore likely to have concentrated amounts of lectins. These include some herbs from my toolbox, such as astragalus, licorice root, carob and kudzu.

Lectins are generally immunostimulants, and herbs containing lectins also generally stimulate the immune system. A lectin from bitter melon does just that [11].

Several plant lectins from grains and legumes are being investigated for cancer treatment [12]. The aforementioned study mentions several mechanisms by which lectins block cancer, which is beyond the scope of this post. Lectins sometimes directly inhibit cancer cells, such as an edible yam that inhibits breast cancer [13].

I would bet that many plant lectins prevent cancer. Therefore, I recommend a plant-based diet with plenty of animal products for people susceptible to cancer who do not have intestinal or autoimmune problems - or other problems characteristic of lectin-sensitive individuals. Plants also have phytate and phytochemicals, which also fight cancer.

My opinion is that lectin sensitivity outweighs potential cancer prevention because lectin-sensitive individuals will have chronic inflammation, which in the long run can lead to cancer and any other chronic disease.

Lectins and CCK

Common lectins from legumes (PHA) cause weight loss in animals [14, 15]. This is usually not a good thing in animal research. While people may see this as a good thing, understand that TNF or inflammation also cause weight loss. Many people with lectin sensitivity may therefore be thin - these people simply eat less (some lectins may also cause weight gain in some, such as wheat germ agglutinin (WGA), which causes leptin resistance).

The possible mechanism by which weight loss is caused is by secretion of a hormone called Cholecystokinin (CCK) and inhibition of alpha-amylase, among other mechanisms [14]. CCK is also released by fat and certain amino acids [16]. CCK can also affect appetite and wakefulness by activating (and inhibiting) orexin [17].

CCK causes the release of digestive enzymes and bile. CCK increases bloating, but in turn usually reduces hunger and the rate at which the stomach empties food [18]. CCK also decreases gastric acid secretion, which slows digestion. The effects of CCK vary among individuals. In rats, for example, CCK reduces hunger in young males, but is slightly less effective in older individuals, and even slightly less effective in females. The hunger-suppressing effects of CCK are also reduced in obese rats [19].

CCK causes anxiety and depression and increases the cortisol/stress response [20, 21, 22]. CCK acts synergistically with 5-ht3 receptors in suppressing appetite (R).

CCK also has stimulatory effects on the vagus nerve, effects that can be inhibited by capsaicin [23]. The stimulatory effects of CCK are opposite to those of ghrelin, which has been shown to inhibit the vagus nerve [24].

The vagus nerve is responsible for heart rate, peristalsis (wave motion in the intestines) and sweating. Activation of the vagus nerve usually leads to a decrease in heart rate and blood pressure. This can occur as a result of bowel problems caused by infections. IBS is thought to cause activation of the vagus nerve, which can lead to fainting, vision disorders and dizziness. People with brain fog often report visual symptoms and this could be a possible cause of this.

Conclusion: Although legumes may be able to help you lose weight, they increase bloating.

Lectins and digestion

Legume lectins can also interfere with digestion and absorption and cause intestinal damage [25].

The disadvantages of lectins

While some lectins are beneficial, there are other lectins such as ricin that are directly lethal with just one molecule. Lectins thus fall into a spectrum from beneficial to lethal, with many being toxic and pro-inflammatory to varying degrees.

In 1988, a hospital launched a "healthy eating day" in the staff cafeteria during lunch. One dish contained red kidney beans and 31 servings were served. At 3 p.m., one of the customers, a surgical assistant, vomited in the operating room. In the following four hours, 10 more clients vomited, some with diarrhea. All had recovered by the next day. No pathogens were isolated from the food, but the beans contained an abnormally high concentration of the lectin phytohemagglutinin.

One of the most harmful lectins is wheat germ agglutinin, which is found in wheat.

Wheat lectin is nature's ingenious solution to protect the wheat plant from all natural enemies. Fungi have cell walls composed of a polymer of N-acetylglucosamine. The cell walls of bacteria are made of a layered structure called peptidoglycan, a biopolymer of N-Acetylglucosamine. N-Acetylglucosamine is the basic unit of the biopolymer chitin, which forms the outer covering of insects and crustaceans (shrimp, crab, etc.). All animals, including worms, fish, birds and humans use N-Acetylglucosamine as the basic substance for building the various tissues in their bodies, including bones. The production of cartilage, tendons and joints depends on the structural integrity of N-Acetylglucosamine. The mucus known as the glycocalyx, or literally "sugar coating," is secreted in humans by the epithelial cells that line all mucous membranes, from the nasal cavity to the top and bottom of the digestive tract, as well as the protective and slippery lining of our blood vessels. The glycocalyx is composed largely of N-Acetylglucosamine and N-Acetylneuraminic acid (also known as sialic acid), with the carbohydrate end of N-Acetylneuraminic acid of this protective glycoprotein forming the terminal sugar that is exposed to the contents of both the intestine and the arterial lumen (orifice). The unique binding specificity of WGA to exactly these two glycoproteins is not accidental. Nature perfectly designed WGA to adhere to, disrupt and invade these mucosal surfaces.

Soy agglutinin or SBA also has a bad reputation and binds to the intestines.

I think most people who are gluten sensitive are more likely to be sensitive to WGA, a lectin in wheat.

Studies have shown that WGA actually inhibits the accumulation of the vitamin D receptor in cells.

An interesting action of WGA in the body is its relationship with insulin receptor sites. WGA binds directly to insulin receptor sites. A 1973 study states that "wheat germ agglutinin is as effective as insulin in increasing the rate of glucose transport and inhibiting epinephrine-stimulated lipolysis in isolated adipocytes." The study specifically states that glucose transport to fat and liver cells increases, while blocking the ability of stored fat to be released. This can make losing weight impossible, and having more glucose transported to the liver can increase the amounts of triglycerides in our blood.

WGA is a lectin protein that protects wheat from pests. Like gluten, WGA increases intestinal permeability and damages the intestinal wall. This causes our immune system to initiate an immune response and can lead to various autoimmune diseases. WGA also appears to enlarge the intestine through a process of endocytosis. In this process, cells literally gobble up the lectin protein. It has also been shown to interfere with metabolism. Once WGA enters the bloodstream, it is deposited in various cells and the blood wall. WGA also causes an increase in the size of the pancreas and a decrease in the size of the thymus [26].

This study states that WGA acts on intestinal cells and accumulates in the cells [27].

WGA and ConA (a lectin in legumes) were found to bind to animal vasotocin neurons [28], which are very similar to human vasopressin and oxytocin. Vasopressin is located in the hypothalamus and prevents frequent urination, but also has cognitive effects, among other things. I noticed that the more lectins I ate, especially wheat, the more I had to urinate. I have seen others with this problem and maybe this is the mechanism.

The part of the hypothalamus that secretes GnRH is also a target of lectins [29]. This is supported by the fact that the neurons that release this hormone have sialic acid in the medial basal [30]. GnRH is responsible for sexual behavior and testosterone production.

The medial basal neurons in the hypothalamus are also involved in sleep regulation (R) and could explain why some people with lectin sensitivity have sleep problems. The medial basal hypothalamus is not protected by the blood-brain barrier [31]. Lectins that cross the intestinal barrier, such as WGA, can reach these areas.

Note that everyone is affected by lectins, but not everyone is harmed by them. Why this is so, I will discuss in future posts.

Although not everyone with inflammation is equally sensitive to the same lectins, there are similarities and common denominators regarding the troublesome lectins. Wheat germ agglutinin gives many people problems, which is why people with autoimmune diseases are against wheat.

Wheat gliadin, which causes celiac disease, contains a lectin-like substance that binds to the human intestinal mucosa [32]. This lectin is particularly resistant to degradation by various means. Several other lectins bind to the intestinal mucosa because the intestine is rich in the carbohydrates to which lectins bind.

The gut has a huge concentration of glycoproteins in general and is also a target of many lectins.

Some food lectins such as peanuts get past the intestinal wall and deposit in distant organs [33].

Common bean lectins such as Concanavalin A and Phytohemagglutinin can activate the immune system [34].

The lectins that enter the bloodstream, such as WGA, are particularly good at activating the immune system.

Most lectins survive digestion through the gastrointestinal tract. Lectins can affect intestinal epithelial cell turnover and loss, damage the luminal membranes of the epithelium, interfere with digestion and absorption of nutrients, stimulate shifts in bacterial flora, and modulate the immune status of the digestive tract [35].

Systemically, they can disrupt fat, carbohydrate and protein metabolism, promote enlargement and/or atrophy of major internal organs and tissues, and alter hormonal and immunological status [35].

Lectins can cause leptin resistance [36], which explains why some people lose weight on a diet low in lectins. Leptin is the satiety hormone. When leptin levels are high but we are still not satiated, there is leptin resistance.

Serotonin transporters are "glycoproteins," meaning they are a target of some lectins. Lectins from wheat, grains, legumes and nuts can bind to these transporters [2], disrupting their function.

Not only are the transporters affected, but more importantly, the receptors are made of glycoproteins (sialic acid), meaning they are sitting ducks of common plant lectins from grains, legumes and nuts [3].

The intestines produce up to 90% of the serotonin used in our bodies, and it is the intestines that are in direct contact with lectins.

As you can imagine, this can lead to serotonin deficiency.

There seems to be no difference in sensitivity to lectins in Th1 and Th2 dominance, but whichever dominance you have, it seems that lectins exacerbate the situation.


Symptoms of sensitivity to lectins

If you have autoimmune or other inflammatory conditions, you are likely to get inflammation from food. The following is a list of symptoms that are common in people with lectin sensitivity. This list is not exhaustive.

I think up to 40% of the population has some degree of lectin sensitivity, but perhaps only 25% have it at a level that causes significant discomfort. This 25% of the population I recommend adhering to this diet. The other percentage can follow the resistant starch diet.

Lectin sensitivity is on a spectrum, with people having varying degrees of sensitivity.

The more symptoms you have, the more likely you are to have lectin sensitivity.

The following symptoms may occur if you eat lectins:


  • Immune imbalance (see if you are Th1 dominant or Th2 dominant) or other autoimmune disorders.
  • Bloating:
  • Bowel problems: Gas/abdominal pain/irritated bowels
  • Fatigue, especially after meals
  • Fog in the brain
  • Excessive anxiety, perfectionism, procrastination, paranoia, OCD and the inability to let go. These indicate low serotonin levels.
  • Skin problems (not acne) - indicative of a disturbed immune system. Histamine response/vasodilation in the skin. Skin problems may include various fungi, eczema, psoriasis, etc.
  • Not properly managing glucose or carbohydrates (often becoming hypoglycemic)
  • Joint pain - in random places such as knee and finger.
  • Pain in random places such as back pain, etc. (which is not the result of a serious injury, of course)
  • Weight problems: Inability to gain weight or persistent weight loss
  • Water retention, puffiness around the eyes, limbs
  • Some types of headaches/migraines
  • Sleep and circadian problems
  • Declining motivation
  • Declining libido
  • Cold limbs
  • Pregnenolone drops
  • Serotonin drops
  • Hypersensitive to physical stimuli
  • Less emotionally stable
  • Desire for food increases
  • Low T3


Why are some people more sensitive to lectins than others?

This is a subject of ongoing research.

Sensitivity to lectins generally stems from an overactive nervous system. CRH plays a major role in this.

My proposed mechanisms for lectin sensitivity are:


CRH - which causes increased permeability, slower intestinal flow, less cannabinoid activation in the gut, local inflammation and SIBO. CRH increases Th1 dominance, Nf-kB, IL-1b (by 8.5X), IL-6 (7.3X), TNF (13X), MHC-II (HLA-DR) and ICAM-1 expression. CRH also increases TLR-4.

Reduced blood supply to the intestines due to an overactive nervous system

Cytokines or immune activation by infection, biotoxin, etc... increase the likelihood of a response to lectins.

CCK, which is increased by lectins

Toll-Like Receptor activation by genetics, CRH, toxins or infections.

Less Tregs or Treg function and less IL-10

Less Cannabinoid receptor activation

Less sialic acid in the intestines

Lower HCl secretion caused by stress, other factors

People have different levels of how "sialylated" their intestines are or how much sialic acid they have in their intestines. I did a lot of experiments with coconut oil. I found that consuming a lot of coconut oil made me less sensitive to food, even though it gave me other types of systemic inflammation that did not come from food. I found a study that showed that sialic acid levels in the intestines (particularly the brush border membranes) increased in response to eating coconut oil [37]. Because my sialic acid levels were increased in my gut, this may have attenuated the effect of lectins.

Blood type A has N-acetylgalactosamine in the cell. It would be interesting to see if people with this blood group, like myself, are more sensitive to lectins.


How does Paleo fit into this?

I am not a big fan of the paleo movement (or any other movement for that matter) because I think it is rigid and most absolute. I also don't believe in the ideology behind it.


When I hear paleo bloggers talk about how everyone can't stand grains, I think that's silly. Many people eat grains without health problems. That is an observable fact.


This rigid dogma combined with seeing carbs as the evil and fat as the healthiest ingredient has alienated me from this movement. I think the movement has been hijacked by "marketers." (marketers= marketers who profit).


Paleo can also be confusing. 


I prefer to think in less absolutist terms. Instead of categorizing things as good or bad, I like to understand how they are harmful and why people are not harmed in the same way.


However, with all the shortcomings of paleo, the diets of most paleo proponents are lower in lectins, making this diet especially beneficial for people with autoimmune problems.


Clinical research on lectin avoidance and autoimmune diseases

I would like to mention a study highlighting the role of lectins in autoimmune diseases.


This study was conducted on 800 people with autoimmune diseases who ate a diet that consisted of avoiding grains, sprouted grains, pseudo-grains, beans and legumes, soy, peanuts, cashews, nightshades, melons and pumpkins, and non-South European cow's milk products (Casein A1), and grain- and/or bean-fed animals.


Most of these people had elevated TNF-alpha. The result after 6 months was a normalization of TNF-alpha in all patients who adhered to the diet.


The study concluded that elevated Adiponectin is a marker for lectin and gluten sensitivity, while TNF-alpha can be used as a marker for gluten/lectin exposure in sensitive individuals. [1]


These results are amazing and confirm my suspicions: people with autoimmune problems should stay away from lectins.

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