Key points
- Lectins are found in a wide variety of foods
- They have a range of actions, some beneficial but also often damaging
- Toxic lectins from plants can act as ‘anti-nutrients’ that can inhibit digestion and also cause intestinal damage and systemic effects
- However, plant lectins are typically removed in large enough quantities to remove the negative health effects for most people; through cooking, fermentation, sprouting, or extraction techniques
Lectins has become a bit of a buzz-word in nutrition. Many people claim that lectins from foods have serious health implications and various ‘lectin-free’ diets have become popular. But lectins are common throughout the body and in all sorts of foods and can have vastly different effects depending on whether they are internally created, taken in from food, and also depending on how the food has been processed.
What are lectins?
Lectins are a type of protein found in both animals and plants, and in many foods, that binds to carbohydrates. Because of this ‘binding’, they can be involved in many processes throughout the body, including both inflammatory and anti-inflammatory actions, binding of cells and viruses to a target tissue, and many other actions.1, 2 The actions of some lectins are positive within the body, while others can be highly toxic.
Why are lectins important?
The lectins found naturally in the human body have a range of actions that aid the function of the body but some lectins from food, particularly those found in some legumes are toxic and because of this, ‘lectin-free diets’ have become popular.
Raw plants contain toxic lectins that act as ‘anti-nutrients’ that can reduce the ability of the body to properly assimilate protein, carbohydrate, and essential minerals, and that can cause red blood cells to clump together (hemagglutination) reducing oxygen delivery, and potentially clogging arteries. These lectins can also cause allergic reactions and might be a cofactor in autoimmune reactions.
What does the research say?
Wheat, other grains, and legumes have high concentrations of a variety of lectins. Soybeans and kidney beans are particularly high in lectins. In humans, these plant lectins have been linked to food poisoning, haemolytic anaemia, jaundice, digestive distress, protein and carbohydrate malabsorption and allergies.3-5 Lectins from beans can also cause autoimmune and allergic effects and gastrointestinal damage,6 and isolated lectins might also cause damage to the intestinal wall.5
So, while these lectins are known to have a range of negative effects on health, these negative effects are generally not observed from cooked or properly prepared foods.4, 5 Some isolated lectins could also offer the potential for health benefits due to their possible antioxidant,7 anti-tumour and anti-HIV activity.6, 8-10
What does this all mean?
Lectins from plant foods like legumes and grains can be toxic and cause damage to the intestinal wall and a range of allergy and immune effects. However, lectins can be effectively removed or sufficiently reduced by proper cooking, fermentation, and extraction techniques.
References
1. Espino-Solis GP. Lectins: A brief review. Vitae. 2015;22:9-11.
2. Siew JJ, Chern Y. Microglial Lectins in Health and Neurological Diseases. Frontiers in molecular neuroscience. 2018;11(158).
3. Kumar KK, Chandra KLP, Sumanthi J, Reddy GS, Shekar PC, Reddy B. Biological role of lectins: A review. Journal of orofacial sciences. 2012;4(1):20.
4. van Buul VJ, Brouns FJPH. Health effects of wheat lectins: A review. Journal of Cereal Science. 2014;59(2):112-7.
5. Sandarani M, Kulathunga K. A Brief Review: Lectins, Protease Inhibitors and Saponins in Cereals and Legumes. Asian Food Science Journal. 2019:1-4.
6. He S, Simpson BK, Sun H, Ngadi MO, Ma Y, Huang T. Phaseolus vulgaris lectins: A systematic review of characteristics and health implications. Critical Reviews in Food Science and Nutrition. 2018;58(1):70-83.
7. Singh SR, Tatke PA, Naharwar VP. Lectins from Vigna radiata – A potential health supplement. Planta Med. 2011;77(12):PJ8.
8. Souza MA, Carvalho FC, Ruas LP, Ricci-Azevedo R, Roque-Barreira MC. The immunomodulatory effect of plant lectins: a review with emphasis on ArtinM properties. Glycoconjugate journal. 2013;30(7):641-57.
9. Ghazarian H, Idoni B, Oppenheimer SB. A glycobiology review: Carbohydrates, lectins and implications in cancer therapeutics. Acta Histochemica. 2011;113(3):236-47.
10. Akkouh O, Ng TB, Singh SS, Yin C, Dan X, Chan YS, et al. Lectins with Anti-HIV Activity: A Review. Molecules (Basel, Switzerland). 2015;20(1):648-68.
