Previously published 25/10/2018.

What are lectins?

Lectins in plants are a line of defence against microorganisms, pests, and insects; a defence mechanism for seeds to remain intact as they passed through animals’ digestive systems, for later dispersal. Lectins are resistant to human digestion and they enter the blood unchanged.

Lectins are a type of protein that can bind to cell membranes by attaching to a sugar anchor and offer a way for molecules to stick together without getting the immune system involved, which can influence cell-to-cell interaction.
Lectins are abundant in raw legumes and grains and are most commonly found in the part of the seed that becomes the leaves when the plant sprouts, but also on the seed coat (bran). They’re also found in dairy products and certain vegetables. While lectin content in food is fairly constant, the genetic altering of plants has created some fluctuations. Plus, we eat a lot more grains than we are supposed to. Our western diet is actually based on grain and grain products, which are often highly processed and in many different ways.

Lectins are thought to play a role in immune function, cell growth, cell death, and body fat regulation.

Because we cannot digest lectins, we often produce antibodies to them.
Almost everyone has antibodies to some dietary lectins in their body.
This means responses vary between individuals and can create intolerances or give the same symptoms as gluten intolerance or lactose intolerance for example.

There are some lectins that no one should consume.

Red Kidney Beans, for example, should never be made to sprout. This is due to their of phytohaemagglutinin — a lectin that can cause red kidney bean poisoning.
​The poisoning is usually caused by ingesting raw, soaked kidney beans. Just a few beans can trigger symptoms — raw Kidney Beans contain from 20,000–70,000 molecules (Lectins), while fully-cooked beans usually contain a lot less, about 200–400.

While many types of lectins cause negative reactions in the body, there are also health-promoting lectins that can decrease the incidence of certain diseases. The body also uses lectins to achieve many basic functions, including cell-to-cell adherence, inflammatory modulation and programmed cell death.

As previously explained, lectins can cause damage to the gut wall by attaching to a sugar anchor, present on the cell membrane itself. Although it causes very minor damage to the lining of the GI tract, it is normally repaired very quickly. Since the purpose of the gut lining is to let the good stuff through and keep the bad stuff contained in the lumen of the gut, it’s important for the cellular repair system to be running at full efficiency.

Sometimes, Lectins can impact gut wall repair and overwhelmed cells cannot regenerate as fast as they need to in order to keep the intestinal lining secure — compromising the gut's integrity, a leading cause of “leaky gut”. Larger molecules can therefore enter the bloodstream and cause havoc — a much broader immune system response as the body’s defences move in to attack the invaders. Symptoms can include acne and skin rashes, joint pain, and many symptoms associated with systemic inflammation.

When someone suffers from Crohn’s disease or irritable bowel syndrome, the gut lining seems to be more sensitive to food lectins. This might be due to the high turnover of cells and the greater presence of immature cells.

Unrefined grains are more nutritious than refined versions because they contain more nutrients. However, they also provide more lectins (and other anti-nutrients. e.g. phytic acid, also known as phytate).
While this was likely never a problem when we grew and harvested our own grains, we now have access to MANY whole grain products. Before the invention of modern agriculture, grains were a minor and seasonal crop. Now we can go to the supermarket and leave with a cart full of pasta, bread, rice, quinoa, amaranth, oats, barley, and more besides.

How to reduce your exposure to lectins and phytic acid?

Soaking, fermenting, sprouting and cooking will decrease lectins and free up essential nutrients.

Soaking beans and legumes overnight; changing the water a few times; adding sodium bicarbonate to water may help neutralise lectins further; and so, draining and rinsing again before cooking.

Fermentation allows beneficial bacteria to digest and convert many of the harmful substances (sourdough bread or beer, which are still considered fermented grains).

Cooking with seaweed can help reduce the lectin and phytate content, especially when cooking beans and legumes, as seaweed can attract and trap them and be eliminated via the bowel.

Some experts hypothesise that it is no coincidence that the top eight allergens also contain some of the highest amounts of lectins (e.g., dairy, egg, wheat, soy, peanuts, tree nuts, fish and shellfish).

References

• Sanchez, O. (2021). The truth about grains. in: Energise - 30 Days to Vitality. Nutrunity Publishing. London. pp. 123-151.

• Deshpande SS. Handbook of Food Toxicology. 2002.

• Imir, T. Bankhurst, AD. (1987). Inhibition of Natural Killer and interleukin 2-activated NF cell cytotoxicity by monosaccharides and lectins. Mikrobiyoloji Bülteni (Bulletin of Microbiology). 21, pp. 245-250.

• Chamaillard L, et al. (1993). Polyamine deprivation stimulates natural killer cell activity in cancerous mice. Anticancer Research. 13, pp. 1027-1033.

• Luk, GD. et al. (1988). Biochemical markers in colorectal cancer: diagnostic and therapeutic implications. Gastroenterology Clinics of North America. 17, pp. 931-940.

• Erickson, RH. et al. (1985). Effect of lectins on the activity of brush border membrane-bound enzymes of rat small intestine. Journal of Pediatric Gastroenterology and Nutrition. 4, pp. 984-991.

• Grant, G. (1982). Anti-nutritive effects of soybean: A review. Journal of Animal Science. 55, pp. 1087-1098.

• Watzl, B. et al. (2001). Dietary wheat germ agglutinin modulates ovalbumin-induced immune responses in Brown Norway rats. British Journal of Nutrition. 85, pp. 483-490.

• Falth-Magnusson, K. et al. (1995). Elevated levels of serum antibodies to the lectin wheat germ agglutinin in celiac children lend support to the gluten-lectin theory of celiac disease. Pediatric Allergy and Immunology. 6, pp. 98-102.

• Hollander, D. et al. (1986). Increased intestinal permeability in patients with Crohn’s disease and their relatives. A possible etiologic factor. Annals of Internal Medicine. 105, pp. 883-885.

• Pusztai A. (1993). Dietary lectins are metabolic signals for the gut and modulate immune and hormonal functions. European Journal of Clinical Nutrition. 47, pp. 691-699

• Pusztai, A. et al. (1993). Antinutritive effects of wheat germ agglutinin and other N-acetylglucosamine-specific lectins. British Journal of Nutrition. 70, pp. 313-321.

• Hoss, VK. Raabe, G. Muller, P. (1976). Lectin arthritis: A new arthritis model. Journal of Allergy and Clinical Immunology (Leipz). 22, pp. 311-316

• Braun, J. Sieper, J. (1999). Rheumatologic manifestations of gastrointestinal disorders. Current Opinion in Rheumatology. 11, pp. 68-74.

• Cordain, L. et al. (2000). Modulation of immune function by dietary lectins in rheumatoid arthritis. British Journal of Nutrition. 83, pp. 207-217.

• Livingston, JN. Purvis, BJ. (1980). Effects of wheat germ agglutinin on insulin binding and insulin sensitivity of fat cells. American Journal of Physiology. 238, E267-E275.

• Freed, DJ. (2002). Dietary Lectins. in Brostoff and Callacombe: Food Allergy and Intolerance. Bailliere Tindale Publishers, London.

• Shemer, J. LeRoith, D. (1987). The interaction of brain insulin receptors with wheat germ agglutinin. Neuropeptides. 9, pp. 1-8.

• Ponzio, G. et al. (1990). Wheat germ agglutinin mimics metabolic effects of insulin without increasing receptor autophosphorylation. Cellular Signalling. 2, pp. 377-386.

• Shechter Y. (1983). Bound lectins that mimic insulin produce persistent insulin-like activities. Endocrinology. 113, pp. 1921-1926.

• Kitano, N. et al. (1988). Detection of antibodies against wheat germ agglutinin bound glycoproteins on the islet-cell membrane. Diabetic Medicine. 5, pp. 139-144.

• Hokama, A. et al. (2008). Roles of galectins in inflammatory bowel disease. World Journal of Gastroenterology. 14, pp. 5133-5137.

• Rabinovich, GA. Toscano, MA. (2009). Nature Reviews Immunology. 9, pp. 338-352.

• Hamid, R. Masood, A. (2009). Dietary lectins as disease causing toxicants. Pakistan Journal of Nutrition. 3, pp. 293-303.

• Messina, JL. et al. (1987). Insulin-mimetic actions of wheat germ agglutinin and concanavalin A on specific mRNA levels. Archives of Biochemistry and Biophysics. 254, pp. 110-115.

• Jordinson, M. et al. (1996). Soybean lectin stimulates pancreatic exocrine secretion via CCK-A receptors in rats. American Journal of Physiology. 270(4 Pt I), G653-G659.

• Rudiger, H. et al. (2000). Medicinal chemistry based on the sugar code: Fundamentals of lectinology and experimental strategies with lectins as targets. Current Medicinal Chemistry. 7, pp. 389-416.

• Pierini C. Lectins: Their damaging role in intestinal health, rheumatoid arthritis and weight loss. Available at: https://www.sott.net/article/237196-Lectins-Their-Damaging-Role-in-Intestinal-Health-Rheumatoid-Arthritis-and-Weight-Loss

• Sharon N. (2007). Lectins: Carbohydrate-specific reagents and biological recognition. Journal of Biological Chemistry. 282, pp. 2753-2764.

• Hernandez, JD. Baum, LG. (2002). Ah, sweet mystery of death! Galectins and control of cell fat. Glycobiology. 12, 127R-136R.

• Ibrahim, SS. (2002). Effect of soaking, germination, cooking and fermentation on antinutritional factors in cowpeas. Nahrung/Food. 46(2), pp. 92-95.