What are Lectins; and could I Be Allergic to Lectins?

Wondering what lectins are? Here are the answers.

DEFINITION of Lectins:
Protein or glycoprotein substances, usually of plant origin, of non-immunoglobulin nature, capable of specific recognition of and reversible binding to, carbohydrate moieties of complex glycoconjugates without altering the covalent structure of any of the recognized glycosyl ligands. This group includes monovalent lectins (i.e. bacterial and plant toxins). These lectins bind to sugar moieties in cell walls or membranes and thereby change the physiology of the membrane to cause agglutination, mitosis, or other biochemical changes in the cell. (agglutination- clumping; mitosis-multiplication or division of a cell forming two daughter cells)Lectins were first described in 1888 by Stillmark working with castor bean extracts. Many members of the lectinic protein family agglutinate (clump together) red blood cells. Research done by Ehrlich, considered to be the father of immunology, has shown that feeding small amounts of lectin containing seeds to rabbits caused partial immunity to the toxicity demonstrating lectins are also antigenic (able to induce antigen antibody reactions).

High levels of lectins (specialized proteins) may be found in grains (also known as cereals or pulses), legumes (that is ‘beans’ including peanuts), dairy and plants in the nightshade family. Many other foods contain lectins but are less well studied and the amounts of lectins present are not thought to be as high or as potentially toxic.

Lectins purified from the germinating seeds of wheat (Triticumspp.); bind to carbohydrate moieties on cell surface glycoproteins and are used to identify certain cell populations and inhibit or promote some immunological or physiological activities.

Lectins purified are used to determine one’s blood type (ABO). Lectins from the castor bean are highly toxic and can kill if ingested in even small amounts. Lectins from kidney beans have been implicated as cause in an outbreak of ‘food poisoning’ with no known pathogen.

So what is a lectin actually?

Think of a lectin as a protein containing a key that fits a certain type of lock. This lock is a specific type of carbohydrate. All life forms, plant and animal, insect and fungus have cell membranes that contain carbohydrates that sit within and project from the membrane. If a lectin with the right key comes in contact with one of these ‘locks’ on the gut wall or artery or gland or organ it ‘opens the lock’, that is disrupts the membrane and damages the cell and may initiate a cascade of immune and autoimmune events leading to cell death.

Lectins can be inactivated by specific carbohydrates (technically known as mono and oligosaccarides) which can bind the ‘key’ and prevent the protein from attaching to the carbohydrate ‘lock’ within the cell membrane. Glucosamine is specific for wheat lectin and it is this specificity that may protect the gut and cartilage from cell inflammation and destruction in wheat (or gluten) responsive arthritis.

While various foods and supplements may inactivate some of these toxic lectins it is impossible for such substances to protect the body from them completely. The safest path is avoidance of known toxic lectins. Common foods with known toxic lectins include all soy and wheat products including oils from these substances.

Some of the symptoms and conditions that have been reported to respond include:

  • arthritis, both rheumatoid and osteoarthritis;
  • allergy;
  • asthma;
  • high cholesterol;
  • atherosclerosis;
  • congestive heart failure;
  • high blood pressure;
  • diabetes;
  • low blood sugar;
  • hyperinsulinemia;
  • chronic fatigue;
  • fibromyalgia;
  • all forms of IBS, Crohn’s, colitis, celiac;
  • chronic candida, repeated gut pathogen infections;
  • malabsorption syndromes;
  • failure to thrive;
  • autoimmune diseases such as thyroiditis, lupus, MS, Parkinson’s;
  • dementia, Alzheimer’s;
  • autism;
  • Schizophrenia;
  • osteoporosis;
  • cancer, several types including breast;
  • hypercortisolemia and hypocortisolemia;
  • adrenal insufficiency;
  • post viral syndrome;
  • post traumatic stress syndrome;
  • post polio syndrome;
  • obesity;
  • hormonal imbalances including low testosterone, low DHEA, PMS, and peri-menopausal symptoms and PCOS.

Higher protein has been shown clinically to improve many of these conditions but not all and it is not a wide enough connecting link.

In the 1970s research on lectins, lectinology, began increasing worldwide. For a more scientific overview see the end of this report.

Take a moment and visit the link below before continuing, to see Dr. Freed’s concept of the lectin problem.

BMJ 1999;318:1023-1024 ( 17 April )

Do dietary lectins cause disease?

In English:

Lectins are found in ALL foods, certain foods more than others, and the same food may contain varying amounts of lectins depending on processing, when and where the plant was grown, and species.

The most common potentially ‘toxic’ lectin containing food groups are

  • grains, especially wheat and wheat germ but also quinoa, rice, buckwheat, oats, rye, barley, millet and corn.
  • legumes (all dried beans, including soy and peanuts),
  • dairy (perhaps more so when cows are feed grains instead of grass, a speculation based on research showing transference of lectins into breast milk and dairy.
  • nightshade (includes potato, tomato, eggplant and pepper).

Dairy may be potentially more harmful in pasteurized, processed milk because of the reduction of SIgA, an immunoglobulin that binds dangerous lectins , Biol Neonate 1991;59(3):121-5 Davin JC et al The high lectin-binding capacity of human secretory IgA protects nonspecifically mucosae against environmental antigens.)

Each  of these groups has a history of being implicated as allergenic. Also note that we are including all foods made from these substances, (these substances in all forms, milled grains, flours, oils, vinegars), peanut butter, cereal or legume oils (soy, canola, corn), additives, thickeners, grain vinegar and products containing grain vinegar, grain alcohol including grain based vodka, and all beers and ales. The only non-grain based alcohols are 100% Agave tequila and 100% potato or grape vodka. Grape based alcoholic beverages like wine are probably allowed if you know you tolerate them.

There has been some information that lectins may be inactivated by soaking, sprouting, cooking or fermenting. Soaking legumes over night, draining the water, rinsing and draining again does seem to remove or inactivate many of the lectins. Heating seems to remove others in some foods but not all. There is little data to prove that any of these methods remove lectins completely as few foods have been tested and of those that have lectins many seem to remain after processing.

Excerpt from Plant Lectins , Pusztai A, Cambridge University Press 1991 pg.108

Nachbar and Oppenheim (1980) found 30% of fresh and PROCESSED foods contained active lectins. Lectins from green salads, fruits, spices, seeds, dry cereals and nuts (even after roasting) showed activity of potentially toxic lectins. Some of these lectins interact with serum or salivary components and bacteria from the oral cavity (Gibbons & Dankers, 1981).

Another example of the hardiness of lectins is the study by Klurfeld DM and Kritchevsky D Lipids 1987 Sep:22(9):667-8,

Isolation and quantitation of lectins from vegetable oils.

Results-Unrefined soy oils contained 858-2983 mcg/kg. After refining oils contained 24-55 mcg/kg. Both refined and unrefined soy oil contained soy lectins.

From Plant Lectins A Pusztai 1991 Table 6.9 page 179

Common features of toxic (non-nutritive) effects in lectin-gut interactions.

  1. High degree of resistance to gut proteolysis.
  2. Binding to brush border cells; damage to microvillus membrane; shedding of cells; reduction in the absorptive capacity of the small intestine.
  3. Increased endocytosis; induction of hyperplastic growth of the small intestine; increased turnover of epithelial cells.
  4. Interference with the immune system; hypersensitivity reactions.
  5. Interference with the microbial ecology of the gut; selective overgrowth.
  6. Direct and indirect effects (hormones, etc.) on systemic metabolism.

Especially note #5. The popular Candida Diet is essentially a high protein, low carbohydrate diet which limits starches and sugars and thereby limits lectins. If lectins are a problem for this person (the so-called ‘candida’ patient) lectin ingestion may be associated with overgrowth of various gut pathogens that may include yeasts and removal of lectins would restore the gut ecology and the gut immune system. If this is true, the diet does not get rid of yeast but relieves the person from symptoms and pathogenic consequences caused by ingestion of lectins to which he or she is intolerant.

Lectins are hardy proteins that do not break down easily. They are resistant to stomach acid and digestive enzymes.

Lectins may bind to the gut wall and damage the gut lining, are not altered by digestive enzymes, and may alter gut permeability and pass through the gut into general circulation.
Lectins can cause alterations in gut function that may be related to colitis, Crohn’s Disease, Celiac-Sprue, IBS and gut permeability.

Lectin damage to the gut wall may allow other non-lectin proteins to cross undigested into general circulation and cause allergic reactions, including anaphylaxis.
Having gained access to general circulation various lectins may bind to surface cell membranes in arteries and vessels, organs and glands, including the thyroid, pancreas, kidney and adrenals, in susceptible animals and humans.

This binding may begin antigen antibody reactions leading to autoimmune disorders and so-called degenerative diseases.
Different lectins have been implicated in different diseases. Dairy lectins have been implicated in juvenile onset type I diabetes. Wheat lectins have been implicated in juvenile nephropathy.

Type or types of lectin and one’s susceptibility (genetic susceptibility) cannot be determined by blood type. D’Adamo tested lectins with blood cells. Lectin intolerance reactions occur in the gut, general circulation (artery walls and the like), brain, gland or organ as well as red blood cells. Sensitivity of one type of cell does not necessarily determine whether another type cell will or will not react.

SIgA, and other immune factors may, if sufficient in quantity, help protect against some exposure to toxic lectins. See abstract at end of report.

GM (genetically modified foods) are modified by splicing ‘lectins’ from one plant family to another. This is extremely problematic. If you know you react to a particular plant family but that lectin has been put in a plant not of that family you may consume the ‘toxic to you’ lectin, have the reaction/response and not know the cause.

We are or become lectin sensitive because of:

  • genetics, our ancestors just didn’t evolve eating this type of food and our immune system can’t handle it;
  • a failure of SIgA barrier protection, genetic or environmentally induced;
  • bacterial or virus infection, certain bacteria and virus, including the influenza virus, can damage our cells making them susceptible to lectin antibody/antigen reactions
  • or by the use of NSAIDS (non-steroidal anti-inflammatories) or other drugs which increase gut permeability and allow lectins to enter general circulation.

Historically diagnosis and treatment of Celiac-Sprue related to ‘gliadin’ (also known as gluten) sensitivity. Gliadin is found in wheat, rye, barley, oats, and foods containing these grains (including beer, grain based alcohols, mayonnaise, grain vinegar, etc). Some Celiacs did not respond to elimination of gluten/gliadin. In 1951 Drs. Sidney V. and Merrill P. Haas published Management of Celiac Disease documenting treatment and cure of celiac and cystic fibrosis of the pancreas with a carbohydrate limiting diet introduced as the ‘Specific Carbohydrate Diet’. More information about this diet can be gotten from Breaking the Vicious Cycle E Gottschall, BA, MSc. Kirkton Press Ltd. Baltimore, Ontario, Canada 1998.

In many cases cited in the book, elimination of certain carbohydrates ‘cured’ diagnosed Celiacs after one year and they were able to return to eating gluten containing foods. In hindsight many of the foods eliminated in this plan are high lectin foods known to be associated with gut and systemic inflammatory reactions. Celiac-Sprue is a genetic disorder treated by elimination of offending foods. The response of some to the specific carbohydrate elimination diet would likely mean that the patients who responded did not have classic gluten intolerance, Celiac-Sprue, which requires life long elimination of gluten/gliadin. It suggests that other lectins may cause similar symptoms and overlapping diagnostic and treatment difficulties.

If all cases of lectin intolerance were genetically based reversal of intolerance would not be possible. There must therefore be a subgroup of IBS, Crohn’s, Celiac, colitis that is related to sensitization to food lectins that can be reversed by avoidance of these lectins and a restoration of gut function including SIgA and other immune protectors. Bacteria, virus, or other conditions, drugs or injurious substances acting directly on the gut wall may cause sensitization.

Tests are available to determine SIgA levels, and gut immune reactions to soy, dairy, wheat and egg. These tests do not cover the entire family of lectins, nor would blood or skin tests necessarily show sub-clinical sensitivity reactions. Most of the conditions associated with sub-clinical lectin intolerance appear to be degenerative, often taking extended periods of time to appear and longer to reach life threatening or painful (such as arthritis) stages. Many lectin related conditions may be considered to be ‘autoimmune’.

Awareness of genetically based intolerance to one or more lectin groups is important family information. If you or another family member has such an intolerance other family members need to be aware and test themselves to prevent problems before they begin.

Infectious or drug related food intolerance responses need to be prevented or reversed. These antigen/antibody responses may be reversible but avoidance of offending lectins should be considered for a minimum of one year before reintroduction to test.

Lectins and their possible involvement in degenerative and autoimmune disease is a relatively new science.

This report, as presented, is hypothesis, not yet fully supported by clinical trials and not yet at a stage where we have any idea of how to connect ‘family’ with lectin response. What facts can be supported include-

  • Proteins institute most allergic and antigenic responses.
  • Lectins are proteins found in large amounts in the foods as above.
  • Lectins are not easily removed from foods or rendered harmless to animals and humans.
  • Lectins from soy, peanut and other beans, wheat germ and wheat, milk, peanut oil (and perhaps other seed oils including soy oil) and nightshades, in a variety of clinical studies have shown various damage to gut lining, joints, kidney, pancreas and brain (even able to cross the blood-brain barrier).
  • Lectins found in peanut oil have been implicated in atherosclerosis. Leaving open the possibility that other seed oils contain damaging lectins and that polyunsaturation and free radicals may not be the full picture on the dangers of polyunsaturated fats.
  • You may react to lectin toxicity due to genetics, intensity of exposure, failure of immune factors to protect you, viral infection, bacterial infection or gut permeability induced by medication or infection.
  • Lectin toxicity (antigen-antibody response) can be ‘sub-clinical’ not showing obvious symptoms for many years.


Lectin intolerance is not an ‘allergy’. A person may be lectin intolerant and not have antibodies to the suspect food when given an allergy test whether blood or skin or saliva. A person may be lectin intolerant and because of the damage done by lectins end up having allergic reactions to a food (that does not contain lectin or may have other lectins), other chemicals or the environment. Lectin intolerance means the inability to deactivate the toxic lectin (prevent its binding to your cells) in the confines of your own body, be it in the gut, artery, organ, gland or brain. The lectin then proceeds to invoke immune responses that damage the cell to which it attaches and possibly surrounding cells. This antigen/antibody response may be the key to many or even most autoimmune diseases and many degenerative diseases may need to be reclassified as autoimmune.

If you or other family members are suffering from any of the symptoms, conditions or diseases mentioned in this report consider an elimination diet to test for lectin sensitivity. If you have been diagnosed with Celiac-Sprue by blood and biopsy testing you must remove gluten/gliadin for the rest of your life. For help with this visit http://www.csaceliacs.org/ If, however, elimination of this glycoprotein does not resolve your problem consider other lectin families as possible offenders. It is also possible to be gluten intolerant and intolerant to one or more of the other lectin families.

Elimination Diet: Remove all suspect lectin families (legumes, dairy, etc) for 7 days. Make sure to read labels so that you aren’t consuming a part of the lectin family hidden in a food. On day 8 reintroduce several of the family members, such as, if testing dairy, milk, cheese and sour cream or legumes, soy, kidney bean and peanut butter. Eat some of the family at each meal. Stop all of the family for the next two days. That is 7 days off, one day on and 2 days off. Check your symptoms on the day of testing and the following 2 days. Look for changes in energy, appetite, bowel function, mood, sleep, skin, digestion, anything suspicious. Test only one ‘family’ at a time. You may remove as many groups as you feel are suspect but only reintroduce one family at a time. If you find you must eliminate one or more lectin families retest every six months to see if the intolerance is genetic or induced.

Common groups: Dairy; legumes (includes soy and peanuts); nuts; seeds; nightshades, includes potato, tomato, eggplant; eggs; grains, esp. gluten grains such as wheat, rye and barley but corn can be an antigen too. Millet, wild rice and plain white rice are usually safe substitutes while testing grains.

Most persons are aware that there are certain foods they seem to ‘react’ to. Symptoms could be obvious, such as gas, bloating, diarrhea or constipation (or both, alternating). Less obvious symptoms may include headache, fatigue, ‘indigestion’, skin problems including hives, psoriasis, swollen joints or water retention.  While some symptoms while resolve quickly after eliminating an offending family other symptoms may take 6-12 months. Be patient. If you are genetically intolerant you will never be able to consume that group of foods safely.

Some symptoms may occur chronically and may seem in no way related to a gut/food or lectin intolerance reactions. This group of symptoms includes the so-called degenerative diseases and autoimmune diseases like those mentioned in the list at the beginning of this report including atherosclerosis, hypertension, osteoporosis, senile dementia, osteoarthritis and rheumatoid arthritis, inflammatory joint diseases, fibromyalgia, chronic fatigue, and adult onset diabetes. Obesity has been associated with consumption of ‘enemy’ lectins.

If your condition responds to elimination of one or more of the high lectin groups, consider your intolerance to be at minimum, induced by the environment (infection or medication induced), and continue to restrict your diet for one year before testing a food-lectin group for re-inclusion. If you again react consider your intolerance a probable genetic inheritance and avoid this type of lectin containing food group as completely as you are able.

For severe symptoms or conditions eliminate all of the major suspect groups, all grains, all legumes, and all dairy. Add the nightshades, potato, tomato, eggplant and pepper, to your restricted list if your symptoms are associated with rheumatic or arthritic complaints. If you respond to this elimination diet by a resolution of symptoms keep out the food group/s for a minimum of six months to one year before reintroducing the group/s. If symptoms reappear consider lifelong avoidance. Rarely does a person have to eliminate more than one or two of the lectin families on a long-term basis. You must let your body decide.


Throughout our history our ancestors had limited exposure to many lectin families depending on location. In our modern world it is common to believe that we can eat any food we like. We can but the food we eat may not like us. Some persons (a minority) can tolerate all foods. For the rest of us most will find one or more lectin groups they do not tolerate. Of those who experience antigen responses most will not need to eliminate more than one or two major lectin groups. You have to experiment and see ‘who’ you are and ‘what’ your ideal foods are. It is a process.

Consider the group most likely to be causing a problem:

  • Deadly nightshades including tomato, potato and eggplant.
  • Glutens found in wheat, rye, barley, malt, and oats.
  • Legumes, all beans including soy and peanut.
  • Dairy including all milk products, milk, cheese, cottage cheese, yogurt, kefir.
  • Eggs

These are the most common lectin families that cause problems. Eliminate the suspect group for 7-10 days. Don’t eat any of the group. Check to make sure none of the lectins are contained in other foods you consume. Example: Vinegar  is made from grain and contains gluten unless it is apple cider vinegar or wine vinegar. Mayonnaise contains gluten because it is made with grain vinegar.

After abstaining for 7-10 days eat a significant amount of the suspect group over one day. Eat other foods as well. Do not eat any more of the test group for two days after the test day.

Look for symptoms of intolerance: bowel changes, sleep changes, mood changes, memory impairment or any other significant changes you can relate to the ingestion of the food group. It may take a day or so for the symptoms to appear. If you think you have found a lectin incompatibility avoid the food. You can test again in a few weeks. If every time you avoid the food your symptoms resolve and every time you eat it they return you have found a lectin you should not eat.

Books mentioned at the beginning of this report by Atkins, Eades, Audette, or any of the authors promoting the Paleo Diet (Hunter-Gatherer) are good resources for menus. Eades and Atkins have some recipes that include dairy, soy and nightshade, some of the suspect foods, so don’t choose those recipes. None of Audette’s recipes use any major lectin groups. It does have some recipes with nightshades. Watch out for those recipes if you think it is a group you react to. Fallon and Enig’s Nourishing Traditions is still a great cookbook just watch out for the lectin containing foods, from the group/s you are avoiding, in recipes.

There are support groups for gluten intolerance, dairy intolerance and soy intolerance but since the idea of lectin intolerance and the broadness of the groups is so new you will have difficulty finding support and information in one place.

If you or your physician need more information, support or research citations I can be reached at K. Sullivan, PO Box 6988, Incline Village, NV 89450-6988. 1-775-831-0292. As I am a educator/consultant and this is how I pay my bills there is a consult fee for my time. I cannot provide individual consultation/information to persons who are not my private clients for both legal and medical reasons. Using the elimination and reintroduction technique describe above will allow most persons to determine their lectin sensitivities.

The following link takes you to an article that explains some of the current concepts in lectinology.

Introduction to “Lectin”

Jun Hirabayashi (Teikyo University Faculty of Pharmaceutical Sciences)

This article also mentions animal lectins which are not at this time considered to be potential toxins/allergens for humans. We are concerned with the more commonly known and studied potentially toxic/allergenic plant lectins as listed above.

To sum this all up: Lectins are:

  • important,
  • in most foods, with plant foods containing the highest levels of known toxic lectins
  • while they have existed as long as life has existed they are not yet well researched or understood.
  • Lectins can be extremely toxic, causing rapid death, or
  • May in some situations and in some species be useful in preventing or reversing conditions and illnesses such as cancer.
  • Most lectins fall somewhere in between these two extremes allowing the possibility of subclinical conditions which appear over time and which don’ t appear to be directly related to lectin exposure.

This article is a brief, edited version of THE LECTIN REPORT by K. Sullivan.  Please use the link to view the full report.

3 thoughts on “What are Lectins; and could I Be Allergic to Lectins?

  1. I've had digestive issues my whole life, and only got relief when dieting to lose weight, which would inadvertantly exclude many of the high leptin foods. My body would start functioning normally again after 4 months of dieting. Eating these foods in small amounts over the years was tolerable, but I decided to get testing, and put everything back into my diet for 3 months to see what I was intolerant to. I'm gluten, dairy, and soy intolerant along with many other foods including peanuts, and a few beans. I don't think the nightshade family affects me since I don't have an ounce of arthritis at 61, but have had joint pain a few times that felt like arthritis, so I'll watch the nightshades too. I think I have had leptin intolerance my whole life. I would eat bread and gain weight fast, and take it off just as fast once I stopped eating it. I've got candida and chronic fatigue to battle as well. I can now see what leptin has done to me. I will be careful in the future to keep these foods out fo my diet completely, or, if only intolerant due to illness, bacteria and viruses, and not genetic, will eat these foods sparingly for the rest of my life.

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