Are lectins harmful? The short answer is it depends. It depends on the type of lectin, the individual, and the dosage.
People with inflammation issues, autoimmune disease or unexplainable health issues should experiment avoiding lectins from ALL grains, beans/legumes, nuts and potatoes/tubers (all kinds) for a period of 4 weeks. If you stay away from most lectins or cut out grains and eat legumes or nuts, this won’t cut it. Seeds may also be problematic for some, but it’s less common.
A study was done on 800 people with autoimmune conditions who ate a diet that consisted of avoidance of grains, sprouted grains, pseudo-grains, beans and legumes, soy, peanuts, cashews, nightshades, melons and squashes, and non-Southern European cow 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 complied with the diet.
Anyone with gas or GI problems should realize that lectins are likely the most significant cause (stress is also significant).
For healthy individuals with no inflammatory issues, I would recommend soaking and sprouting grains, legumes and nuts whenever possible. Whole grains have more lectins than refined grains. Seeds are better sprouted but less important.
People with anxiety-based disorders and/or gut problems should seriously consider a diet that limits lectins because lectins bind to serotonin receptors and transporters disrupting their function [2, 3].
Lectins were the root cause of a good portion of my health issues. People with obscure health issues try to fix them with a whole bunch of insignificant changes. Lectins are the most significant cause of autoimmune disease in my opinion.
The SelfHacked Lectin Avoidance Diet Cookbook, along with the companion guide, includes the science and the details about how to implement the elimination diet in order to figure out things that cause your issue. That way, you can figure out the diet that’s best for you.
What Are Lectins?
Lectins are proteins that bind to carbohydrates and are present in all forms of life, including plants, humans, bacteria, and viruses.
The Benefits of Some Lectins
Lectins have a bad rap, but they’re not all created equal. Some lectins are beneficial.
In plants, lectins appear to be part of the natural defense mechanisms of plants and important for seed survival.
Lectins have many essential roles in the body. For one, they activate the complement immune system (part of the innate immune system), which helps fight pathogens . For example, the lectin pathway helps us fight off pneumonia .
Lectins are generally immunostimulants and the herbs with lectins also generally stimulate the immune system. A lectin from bitter melon does just that .
Various plant-based lectins from grains and legumes are being explored for treating cancer . The referenced study mentions multiple mechanisms by which lectins block cancer, which is out of the scope of this post. Lectins sometimes inhibit cancer cells directly, as is the case of an edible yam inhibiting breast cancer .
I bet many plant lectins are anti-cancer. This is why I recommend plant-based diets with adequate animal products for people predisposed to cancer and who don’t have gut or autoimmune problems – or other problems characteristic of lectin-sensitive individuals. Plants also have phytate and phytochemicals, which are also anti-cancer.
My opinion is that lectin sensitivity outweighs potential cancer prevention because lectin sensitive individuals will have chronic inflammation, which can lead to cancer and every other chronic disease in the long run.
Lectins and CCK
Common legume lectins (PHA) causes weight loss in animals [14, 15]. This is usually not a good thing in animal research. While people may view this as a great thing, you have to understand that TNF or inflammation also causes weight loss. Many people with lectin sensitivity are thin perhaps because of this -these people simply eat less (some lectins can also cause weight gain in some like Wheat Germ Agglutinin (WGA), which causes leptin resistance).
The possible mechanism by which it causes weight loss is by secretion of a hormone called Cholecystokinin (CCK) and inhibiting alpha-amylase, among other mechanisms . CCK is also released by fat and certain amino acids . CCK can also influence appetite and wakefulness by activating (and inhibiting) orexin .
CCK causes the release of digestive enzymes and bile. CCK increases bloating but it usually, in turn, decreases hunger and the rate by which the stomach empties food . CCK also decreases stomach acid secretion, which slows digestion. The effects of CCK vary between individuals. For example, in rats, CCK reduces hunger in young males, but is slightly less effective in older subjects, and even slightly less effective in females. The hunger-suppressive effects of CCK also are reduced in obese rats .
CCK also has stimulatory effects on the vagus nerve, effects that can be inhibited by capsaicin . The stimulatory effects of CCK oppose those of ghrelin, which has been shown to inhibit the vagus nerve .
The vagus nerve is responsible for heart rate, peristalsis (wave-like intestinal movement) and sweating. Activation of the vagus nerve typically leads to a reduction in heart rate and blood pressure. This can occur as a result of gut problems from infections. IBS is thought to cause activation of the vagus nerve, potentially causing fainting, vision disturbances, and dizziness. People with brain fog often report visual symptoms and this may be a potential source for that.
Bottom Line: While legumes can potentially help you lose weight, they increase bloating.
Lectins And Digestion
Legumes lectins can also interfere with digestion and absorption and cause intestinal lesions .
The Harms of Lectins
While some lectins are beneficial, other lectins like ricin will kill instantly with just one molecule. So lectins fall along a spectrum of beneficial to deadly, with many being toxic and inflammatory to various degrees.
In 1988 a hospital launched a “healthy eating day” in its staff canteen at lunchtime. One dish contained red kidney beans, and 31 portions were served. At 3 pm one of the customers, a surgical registrar, vomited in theatre. Over the next four hours, 10 more customers suffered profuse vomiting, 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 phytohaemagglutinin.
One of the most harmful lectins is wheat germ agglutinin, found in wheat.
Wheat lectin is Nature’s ingenious solution for protecting the wheat plant from the entire gamut of its natural enemies. Fungi have cell walls composed of a polymer of N-Acetylglucosamine. The cellular walls of bacteria are made from a layered structure called the peptidoglycan, a biopolymer of N-Acetyl-glucosamine. N-Acetylglucosamine is the basic unit of the biopolymer chitin, which forms the outer coverings of insects and crustaceans (shrimp, crab, etc.). All animals, including worms, fish, birds, and humans use N-Acetylglucosamine as a foundational substance for building the various tissues in their bodies, including the bones. The production of cartilage, tendons, and joints depend on the structural integrity of N-Acetylglucosamine. The mucous known as the glycocalyx, or literally, “sugar coat” is secreted in humans by the epithelial cells which line all the mucous membranes, from nasal cavities to the top to the bottom of the alimentary tube, 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 carbohydrate end of N-Acetylneuraminic acid of this protective glycoprotein forming the terminal sugar that is exposed to the contents of both the gut and the arterial lumen (opening). WGA’s unique binding specificity to these exact two glycoproteins is not accidental. Nature has designed WGA perfectly to attach to, disrupt, and gain entry through these mucosal surfaces.
Soybean agglutinin or SBA also has a bad rep and binds to the gut.
I believe that most people who are gluten sensitive are rather sensitive to WGA, a lectin in wheat.
Studies have shown that WGA actually inhibits cells from accumulating the vitamin D receptor.
An interesting action of WGA in the body is its relationship with insulin receptor sites. WGA bonds directly with the insulin receptor sites. A study published in 1973 states that “wheat germ agglutinin is as effective as insulin in enhancing the rate of glucose transport and inhibiting epinephrine-stimulated lipolysis in isolated adipocytes”. The study states specifically that it increases glucose transport into fat and liver cells while blocking the ability of stored fat to be released. This can make losing weight impossible and the fact that more glucose is getting brought to the liver; it can increase the amounts of triglycerides in our blood.
WGA is a lectin protein that protects wheat from pests. Just like gluten, WGA increases intestinal permeability and damages the gut lining. This leads to our immune system initiating an immune response and can lead to various auto-immune ailments. WGA has also been shown to increase the size of the gut through a process of endocytosis. This is when the cells literally engulf the lectin protein. It was also shown to interfere with metabolism. Once the 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 .
This study states that WGA acts upon gut cells and accumulates within the cells .
WGA and ConA (a lectin in legumes) were found to bind to animal vasotocin neurons , which is very similar to human vasopressin and oxytocin. Vasopressin is found in the hypothalamus and prevents frequent urination, but also has cognitive effects, among others. I found that the more lectins I ate, especially wheat, the more I had to pee. I’ve seen others with this issue and perhaps this is the mechanism.
The part of the hypothalamus that secretes GnRH is also a target of lectins . This is supported by the fact that the neurons that release this hormone in the medial basal have sialic acid . GnRH is responsible for sexual behaviors and testosterone production.
The medial basal neurons in the hypothalamus also involve sleep regulation (R) and could explain why some people with lectin sensitivity have sleep issues. The medial basal hypothalamus isn’t protected by the blood-brain barrier . Lectins that pass the gut barrier such as WGA can reach these areas.
Note that everyone is affected by lectins, but not everyone is harmed by them. I will discuss why this is the case in future posts.
While not everyone with inflammation is equally sensitive to the same lectins, there are similarities and common denominators with regard to the troublesome lectins. Wheat germ agglutinin gives a lot of people trouble, which is why people with autoimmune conditions are against wheat.
Wheat gliadin, which causes coeliac disease, contains a lectin-like substance that binds to human intestinal mucosa . This lectin is particularly resistant to being broken down by various means. Various other lectins bind to the gut mucosa because the gut is rich in the carbohydrates that lectins bind to.
The gut has a huge concentration of glycoproteins in general and is likewise a target of many lectins.
Some food lectins like peanuts get past the gut wall and deposit themselves in distant organs .
The lectins that enter the bloodstream like WGA are especially good at activating the immune system.
Most lectins survive digestion by the gastrointestinal tract. Lectins can affect the turnover and loss of gut epithelial cells, damage the luminal membranes of the epithelium, interfere with nutrient digestion and absorption, stimulate shifts in the bacterial flora and modulate the immune state of the digestive tract .
Systemically, they can disrupt lipid, carbohydrate and protein metabolism, promote enlargement and/or atrophy of key internal organs and tissues and alter the hormonal and immunological status .
Lectins can cause leptin resistance , explaining why some people lose weight on low lectin diets. Leptin is the satiating hormone. When leptin levels are high, but we still aren’t satiated, that’s leptin resistance.
Serotonin transporters are “glycoproteins”, which means they are a target of some lectins. Lectins from wheat, grains, legumes, and nuts can bind to these transporters , disrupting their function.
Not only are the transporters affected, but more importantly the receptors are made of glycoproteins (sialic acid), which means they are sitting ducks of common plant-based lectins from grains, legumes, and nuts .
The gut produces up to 90% of the serotonin used in our body and it’s the gut that directly interacts with lectins.
As you can imagine, this can result in serotonin deficiencies.
There doesn’t appear to be a difference in sensitivity to lectins in Th1 and Th2 dominance, though whatever dominance you are, it seems like lectins make the situation worse.
Symptoms of Lectin Sensitivity
If you have autoimmune issues or other inflammatory conditions then you are probably getting inflammation from food. Here’s a list of symptoms that are common in people with lectin sensitivity. This list is not comprehensive.
I reckon that up to 40% of the population has some level of lectin sensitivity, but maybe only 25% have it to a level that causes significant discomfort. This 25% of the population I recommend keep to this diet. The other percentage can do the resistant starch diet.
Lectin sensitivity is on a spectrum, where people are sensitive to varying degrees.
The more symptoms you have the higher the likelihood of lectin sensitivity.
When I eat lectins, the following symptoms arise, which are common in others as well:
- Immune imbalances (see if you’re Th1 dominant or Th2 dominant) or other autoimmune conditions.
- Gut problems: Gas/Abdominal discomfort/Irritated GI tract
- Fatigue, especially post-meal fatigue
- Brain fog
- Excessive anxiety, perfectionism, procrastination, paranoia, OCD and in the inability to let go. These are indicative of low serotonin.
- Skin problems (not acne) – indicative of an immune imbalance. Histamine response/vasodilation in the skin. Skin problems can include various fungus, eczema, psoriasis, etc.
- Not handling glucose or carbs well (getting hypoglycemic often)
- Joint discomfort – I get pains in random places such as my knee and finger.
- Pain in random places like backaches, etc. (that aren’t a result of a serious injury, obviously)
- Weight problems: Inability to put on weight or stubborn weight loss
- Water retention, puffiness around the eyes, extremities
- Some types of headaches/migraines
- Sleep and circadian issues
- My motivation down
- My libido goes down
- I have cold extremities
- Pregnenolone goes down
- Serotonin goes down
- I become hypersensitive to physical stimuli
- I become less emotionally stable
- My cravings for food go up
- Low T3
Why Are Some People More Sensitive To Lectins Than Others?
This is an area of continuing research.
Lectin sensitivity generally comes from an overactive nervous system. CRH has a big role in this.
My proposed mechanisms for lectin sensitivity are:
- CRH – which causes increased permeability, slower gut 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.
- Less blood flow to the gut from an overactive nervous system
- Cytokines or Immune activation from infection, biotoxin, etc…will increase the likelihood of response to lectins
- CCK, which is increased by lectins
- Toll-Like Receptor activation from genetics, CRH, toxins or infections
- Lower Tregs or Treg function and less IL-10
- Less Cannabinoid receptor activation
- Less gut sialic acid
- Lower HCl secretion, caused by stress, other factors
People have different levels in how much their gut is “sialylated” or the degree to which they have sialic acid in their gut. I’ve done quite a few experiments with coconut oil. I noticed that consuming a lot of coconut oil made me less sensitive to foods, even though it gave me other kinds of systemic inflammation that didn’t come from food. I found a study that showed sialic acid content increased in the gut (specifically the brush border membranes) in response to coconut oil feeding . By having my sialic acid levels in my gut increased, this may have blunted the impact of lectins.
Blood type A has N-acetyl galactosamine in its cell. It would be interesting to see if people with this blood type, such as 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’s rigid and most absolute. I also don’t believe in the ideology behind it.
When I hear paleo bloggers talk about everyone not being able to handle grains, I think that’s silly. Many people eat grains without any health issues. This is an observable fact.
This rigid dogma in combination with viewing carbs as evil and fat as the healthiest ingredient possible alienated me from this movement. I think the movement has been hijacked by “marketeers.” (marketeers= marketers who profiteer).
Also, paleo can be confusing. I had problems with eggs, nuts and some fish, which are considered “paleo.”
I prefer to think of things in less absolutist terms. Rather than categorize things as good or bad, I like to understand how they are harmful and why people don’t get harmed in the same way.
However, with all of the paleo’s inadequacies, the diets by most paleo advocates are lower in lectins, which is why this diet is particularly beneficial in people with autoimmune issues.
If you look at the paleo bloggers, you’ll notice a common theme of people who have autoimmune issues and do better with limiting lectins in their diet (whether they are aware of this or not).
No matter how each individual blogger spins it, the potential benefits arise almost solely, in my opinion, from a reduction in harmful lectins.
Clinical Trial on Lectin Avoidance and Autoimmune Disease
I’d like to mention a study I previously mentioned in my Th1/Th2 post that highlights the role of lectins in autoimmune disease.
This study was done on 800 people with autoimmune conditions who ate a diet that consisted of avoidance of grains, sprouted grains, pseudo-grains, beans and legumes, soy, peanuts, cashews, nightshades, melons and squashes, and non-Southern European cow 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 complied with 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. 
These results are astounding and confirmed my suspicions: people with autoimmune issues should stay away from lectins.
The SelfHacked Lectin Avoidance Diet Cookbook, along with the companion guide, includes details about how to implement the elimination diet in order to figure out things that cause your issue.