IFM’s Advanced Practice Modules (APM) offer insight into a range of clinical conundrums and provide useful clinical pearls on approaching care through the functional medicine lens. Below is a question that is frequently asked by attendees during the program. Stay tuned for more clinical question-and-answers coming soon!
Lectins are carbohydrate-binding proteins that can be found in about 30% of foods, including legumes, seeds, nuts, fruits, and vegetables.1,2 The lectins in phytohemagglutinin have been found to bind to the brush border of the small intestine, affecting tissue growth, development of microvilli, and absorption of nutrients.3 Therefore, high concentrations of lectins can cause nausea, vomiting, bloating, and diarrhea. However, it’s important to note that cooking via soaking, sprouting, fermenting, boiling, and pressure cooking can significantly reduce the lectin content of foods.2
Lectins may also induce IgE and IgG-mediated reactions and have been associated with autoimmunity.1,2 The association between autoimmunity and undigested lectins comes from their ability to disrupt intestinal barrier integrity and induce cross reactivity of antibodies against the lectins themselves, exogenous peptides, and various body tissues through shared amino acid motifs.1,4 In one human study, antibodies (IgG, IgM, and IgE) to lectin were found in the blood of 8-15% of subjects (500 healthy subjects); the IgM anti-lectin antibody levels were also correlated with rheumatoid factor levels (although not with ANA levels), indicating that lectins or the antibodies produced against them may contribute directly or indirectly to autoimmunity.1
However, most studies on lectins are only in-vitro and animal studies. It’s important to consider whether the real concern is non-immune-mediated reactions to wheat and other grains due to their high FODMAP content rather than the high lectin concentration. In fact, there are several benefits to lectins as well. Plant lectins have microbicidal activity, and certain lectins also enhance the phagocytic activity of macrophages during microbial infections.5 Plant lectins have been shown to also promote autophagy and apoptosis and induce immunomodulatory activates.6 Lectins also have beneficial properties including anti-cancer, anti-HIV, anti-microbial, and prevention of mucosal atrophy. Lectins may also reduce type 2 diabetes and obesity by slowing down the absorption of carbohydrates, improving blood sugar and insulin levels.
Clinical takeaway: Research on lectins is limited. There is some evidence to suggest that high concentrations of lectins may cause adverse health effects such as gastrointestinal damage/disease and immune reactions. However, lectins may also have beneficial properties, and complete avoidance for most individuals is not warranted. Additionally, instead of complete avoidance of lectin-rich foods, consider soaking, sprouting, fermenting, boiling, and pressure cooking these foods, which dramatically reduces the lectin content.
Learn more about the connection between IgE and IgG-mediated reactions and autoimmunity about the upcoming Immune Advanced Practice Module (APM).
- Vojdani A, Afar D, Vojdani E. Reaction of lectin-specific antibody with human tissue: possible contributions to autoimmunity. J Immunol Res. 2020;2020:1438957. doi:1155/2020/1438957
- Petroski W, Minich DM. Is there such a thing as “anti-nutrients”? A narrative review of perceived problematic plant compounds. Nutrients. 2020;12(10):2929. doi:3390/nu12102929
- He S, Simpson BK, Sun H, Ngadi MO, Ma Y, Huang T. Phaseolus vulgaris lectins: a systematic review of characteristics and health implications. Crit Rev Food Sci Nutr. 2018;58(1):70-83. doi:1080/10408398.2015.1096234
- Vojdani A. Lectins, agglutinins, and their roles in autoimmune reactivities. Altern Ther Health Med. 2015;21(Suppl 1):46-51.
- Mishra A, Behura A, Mawatwal S, et al. Structure-function and application of plant lectins in disease biology and immunity. Food Chem Toxicol. 2019;134:110827. doi:1016/j.fct.2019.110827
- Bhutia SK, Panda PK, Sinha N, et al. Plant lectins in cancer therapeutics: targeting apoptosis and autophagy-dependent cell death. Pharmacol Res. 2019;144:8-18. doi:1016/j.phrs.2019.04.001