Lectins, dangerous for health or not?

Today I want to talk about lectins. There is some dietary advice and a few diets that support the avoidance of lectins in the diet to prevent leaky gut syndrome, skin disorders and allergies. 

But is this true?

In this post I will examine the effects of lectins on our health and determine whether they are dangerous to our health and what we should do about them.

But, to begin with, what are lectins and where are they found?

Lectins are proteins that bind to carbohydrates.

Lectins are present throughout nature in animals, plants, and microorganisms and are necessary for their survival. This means that lectins are found in almost all foods, and are therefore unavoidable from a dietary standpoint. Lectins are found in some foods in higher concentrations. [1]

The six food groups that contain the most lectins are:

  • Tubers
  • Grains, especially processed grains
  • Beans
  • Dairy Foods, if the milking animal was fed on grains rather than on grass.
  • Nightshade vegetables (tomatoes, potatoes and aubergines)
  • GMO foods: Lectins are often added into the DNA of genetically engineered crops to enhance pest and fungal resistance. 

Lectins have been found in the foods we eat for over 2 million years. 

We would have never made it this far as a species if our bodies could not disable lectins or use them to our advantage. 

Our body also produces lectins. In our body lectins have many functions:

  • Lectins help cells bind together 
  • Lectins protect the cell by helping it differentiate between itself and foreign pathogens or intruding cells. 
  • Lectins help produce immune cells like antibodies. 
  • Lectins also help the body eliminate foreign pathogens and compounds from the body.
  • Lectins are also antimicrobial, they capture microorganisms through their stickiness, and can also inhibit cancer cells and therefore are vital for our health. [1]

In plants the lectins form a protection mechanism that is not dependent on immune function, like our skin serving as a barrier against pathogens.

The hype about lectins being dangerous to our health began in 1999 following a food poisoning that affected a large number of hospital workers after eating a meal containing red kidney beans. 

The investigation found no pathogenic bacteria in the food but did find that the beans had very high levels of the lectin phytohemagglutinin. 

Another study in the UK looked at the incidence of red kidney bean poisoning between July 1976 and February 1989, where 50 incidents were reported and nine events in which nausea, vomiting, and diarrhea developed within 1-7 h of ingestion of the beans. These events were confirmed to have had high levels of the lectin haemagglutinin in the beans.

The adverse effects of consuming raw lectin rich foods:

Just like other animals, humans are vulnerable to the toxicity of lectins. Concentrated amounts can cause digestive issues and other health problems because lectins are not degraded by stomach acid or enzymes, making them virtually resistant to digestion. 

By consuming raw lectin rich foods, the stickiness of lectins allows them to bind to tissues that are more sensitive to their agglutinating effects such as nerve and connective tissue, the intestinal wall and the bladder. The lectins eventually cause damage to the tissue to which they attach themselves.

Lectins from food enter the body through the gut wall by causing lesions in the gut wall. This damage to the gut wall may lead unwanted substances and bacteria to penetrate the gut wall and enter the blood stream.  

Once they enter the body, lectins may also inhibit the absorption of vitamins.

It is suggested that lectin levels increase in processed grains because by removing the seed coat, which constitutes about 10% of the dry bean seeds, influences the concentration of lectins on a unit per weight basis [Deshpande et al., 1982].

Disabling Lectins:

Remember I mentioned that our bodies could disable lectins? Well, monosaccharides (simple sugars) and oligosaccharides (short chains of 2-10 sugar molecules) from our diet will disable lectins by binding to them. This binding prevents their attachment to the carbohydrates within the cell membrane and other tissues and prevents damage to the gut wall. These saccharides are considered soluble dietary fibre and include:

  • Short chains of fructose molecules – Fructo-oligosaccharides (FOS), which are found in many vegetables.
  • Short chains of galactose molecules – Galactooligosaccharides (GOS). These compounds cannot be digested in the human small intestine, and instead pass through to the large intestine. 

These saccharides also promote the growth of Bifidobacteria, gut bacteria which are beneficial to our health and also help break down lectins. 

Solutions:

The best way to reduce the adverse effects of lectins is not by avoiding foods rich in lectins but by consuming high amounts of soluble dietary fiber in the diet. Foods that are rich in FOS include: chicory, Jerusalem artichoke, leeks and all onions, asparagus and burdock. Foods that are rich in GOS include soy beans.

Another excellent way to reduce the adverse effects of lectins is by soaking foods from the list above of the six foods that contain the most lectins. Soaking these foods overnight and then cooking them in boiling water eliminates almost all lectin activity (12, 13).

While raw red kidney beans contain 20,000 to 70,000 hau (hemagglutinating unit), when cooked, these kidney beans contain only 200-400 hau, a major difference.

Lentils, on the other hand, do not need more than 10 minutes soaking in boiling water before cooking to removes all lectins.

A particularly beneficial type of cooking method to remove lectins and also preserve most nutrients in the food is pressure cooking. Pressure cooking can cook foods at very high temperatures and thus are one of the best ways to inactivate all lectins in grains and beans.

Many cultures also germinate or ferment these foods to improve their digestibility and nutrient value while reducing their lectin toxicity.

In fact, gluten proteins are substantially degraded during germination and vitamins C and E, and beta-carotene that are hardly detectable in the dry grains, upon germination, the concentrations of these antioxidant vitamins increases significantly.

To summarize: There is no need to remove lectin rich foods including root vegetables, grains, and beans from your diet. These foods are very beneficial to health and provide a wealth of fiber and so many nutrients, and they are needed for the survival and thriving of a healthy microbiome. These are foods that have supported our species for eons and continue to do so. Instead of removing foods that contain high amounts of lectins, ensure you are getting sufficient intake of oligosaccharides including FOS and GOS from your diet. Also aim to pre-soak these foods and cook them properly before consumption, and if possible, also sprout them for the additional nutritional benefits.

Feel free to comment below and let me know what you liked best about this article.

Thank you for taking the time to read this. I’d be honored if you would share it with your family, friends, and followers by clicking the Like, Tweet, and Share buttons. If you are serious about improving your health no matter what your age or circumstances, and are ready to finally achieve optimal health and lose the weight you’ve been struggling with, then click HERE to check out my online Guerrilla Diet Bootcamp for Healthy and Lasting Weight Loss.

If you are not already on my mailing list where you will receive my weekly articles packed with scientifically based health, and nutrition content, as well as many FREE bonuses and special offers, and much more, then click HERE to subscribe.

References:

  1. Jeffrey D Esko and Nathan Sharon (2009) Chapter 34 Microbial Lectins: Hemagglutinins, Adhesins, and Toxins
  2. Cheung RCF, Wong JH, Ng TB, Naude R, Rolka K, Tse R, Tse TF, Chan H, Sze SCW.  Tuber Lectins with Potentially Exploitable Bioactivities. Curr Med Chem. 2018;25(42):5986-6001. doi: 10.2174/0929867325666180517095308. Freed DL . Do dietary lectins cause disease? BMJ. 1999 Apr 17; 318(7190):1023-4.
  3. Carbonaro M, Grant G, Cappelloni M, Pusztai A. Perspectives into factors limiting in vivo digestion of legume proteins: antinutritional compounds or storage proteins? J Agric Food Chem. 2000 Mar;48(3):742-9.
  4. Rhodes JM. Beans means lectins. Gut. 1999;44:593–594.
  5. J. C. Rodhouse, C. A. Haugh, D. Roberts, and R. J. Gilbert. Red kidney bean poisoning in the UK: an analysis of 50 suspected incidents between 1976 and 1989. Epidemiol Infect. 1990 Dec; 105(3): 485–491.
  6. Yang F, Basu TK, Ooraikul B. Studies on germination conditions and antioxidant contents of wheat grain. Int J Food Sci Nutr. 2001 Jul;52(4):319-30.
  7. Koehler P, Hartmann G, Wieser H, Rychlik M. Changes of folates, dietary fiber, and proteins in wheat as affected by germination. 2007 Jun 13;55(12):4678-83
  8. Oluwole S Ijarotimi, Oluwole A Adeoti, and Oluwaseun Ariyo Comparative study on nutrient composition, phytochemical, and functional characteristics of raw, germinated, and fermented Moringa oleifera seed flour. Food Sci Nutr. 2013 Nov; 1(6): 452–463.
  9. QiangWang, Lu-GangYu, Barry JCampbell, Jeremy DMilton Identification of intact peanut lectin in peripheral venous blood. The Lancet Volume 352, Issue 9143, 5 December 1998, Pages 1831-1832
  10. Lajolo F. and and Genevese M. (2002). Nutritional Significance of Lectins and Enzyme Inhibitors from Legumes, Journal of Agricultural and Food Chemistry, 50(22):6592-8.
  11. Pusztai, A (1991). Plant lectins. Cambridge University Press, Cambridge, UK.
  12. Grant, G and van Driessche, E. (1993). Legume Lectins. Physiochemical and nutritional properties, Recent Advances in Anti-Nutritional Factors in Legume Seeds. Wageningen Pers.
  13. Pusztai, A. and Grant, G. (1998). Assessment of lectin inactivation by heat and digestion. Methods Mol Med., 9:505-14.
  14. Grant, G et al (1982). The effect of heating on the hemagglutinating activity and nutritional properties of bean Phaseolus vulgaris seeds. Journal of the Science of Food and Agriculture, 33, 1324-1326.
  15. Barondes, S. H. (1981). Lectins: Their multiple endogenous cellular functions. Annual Review of Biochemistry, Vol 50: 207- 231.