What is Quercetin?


Quercetin is a natural plant flavonoid found in red onions, capers, kale, and other common foods containing appreciable amounts of quercetin.

What does Quercetin Do?

Mast cells play a part in developing and maintaining leaky gut, as when these mast cells become unstable or degranulate, this causes histamine release.

Histamine is the chemical that causes allergy symptoms, but it can also cause and contribute to leaky gut.

By using quercetin as a mast cell stabilising agent, we can reduce/stop the degranulation and release of histamine and allow the gut lining the opportunity to repair itself.
But quercetin works in another important way for the gut…

Quercetin has also been shown to enhance gut barrier function by having a “sealing” effect due to its role in the assembly and expression of tight junction proteins: zonula occludens-1, occludin, junctional adhesion molecule-A, claudin-3.

By blocking mast cell degranulation, quercetin can also allow the Di-Amine Oxidase (DAO) enzyme to catch up to the backlog of excess histamine, and help reduce food sensitivities/reactions and reduce the burden on the immune system. 

The bioavailability of quercetin in humans is low and highly variable (3-17%), and it is rapidly cleared with an elimination half-life of 1–2 hours after ingesting quercetin foods or supplements.

Quercetins main effect in this product is on the expression of tight junction proteins and stabilisation of mast cells in the lamina propria (the layer just behind the epithelial layer), therefore the low bioavailability and low circulating levels of this flavonol are not necessarily reflective of its efficacy for gut healing as its effects can remain local to the gut, and the absorption will also be dependant on ones barrier integrity; the ‘leakier the gut’ the more quercetin will pass to the lamina propria and the better the flavonol will lower permeability.


Quercetin significantly induces the gene expression as well as the production of Th-1 derived interferon-γ (IFN-γ) and down-regulates Th-2 derived interleukin 4 (IL-4) by normal peripheral blood mononuclear cells (PBMC) 

Quercetin Studies:

Bischoff, S. C., Barbara, G., Buurman, W., Ockhuizen, T., Schulzke, J. D., Serino, M., Tilg, H., Watson, A., & Wells, J. M. (2014). Intestinal permeability-a new target for disease prevention and therapy. BMC gastroenterology14, 189. https://doi.org/10.1186/s12876-014-0189-7

Graefe EU, Wittig J, Mueller S, Riethling AK, Uehleke B. (2001). Pharmacokinetics and bioavailability of quercetin glycosides in humans. Journal of Clinical Pharmacology. 41:492-499. http://ucce.ucdavis.edu/files/datastore/608-67.pdf

Groschwitz KR, and Hogan SP. (2009). Intestinal barrier function: molecular regulation and disease pathogenesis. Journal of Allergy and Clinical Immunology. 124(1):3-20. https://www.ncbi.nlm.nih.gov/pubmed/19560575 

Li Y, Yao J, Han C, Yang J, Chaudhry MT. (2016). Quercetin, inflammation, and immunity. Nutrients. 8(3):167. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4808895/

Pearce, F. L., Befus, A. D., & Bienenstock, J. (1984). Mucosal mast cells. III. Effect of quercetin and other flavonoids on antigen-induced histamine secretion from rat intestinal mast cells. The Journal of allergy and clinical immunology, 73(6), 819–823. https://doi.org/10.1016/0091-6749(84)90453-6

Salehi, B., Machin, L., Monzote, L., Sharifi-Rad, J., Ezzat, S. M., Salem, M. A., Merghany, R. M., El Mahdy, N. M., Kılıç, C. S., Sytar, O., Sharifi-Rad, M., Sharopov, F., Martins, N., Martorell, M., & Cho, W. C. (2020). Therapeutic Potential of Quercetin: New Insights and Perspectives for Human Health. ACS omega5(20), 11849–11872. https://doi.org/10.1021/acsomega.0c01818

Suzuki, T., & Hara, H. (2011). Role of flavonoids in intestinal tight junction regulation. The Journal Of Nutritional Biochemistry22(5), 401-408. doi: 10.1016/j.jnutbio.2010.08.001

Toth S, Jonecova Z, Curgali K, Maretta M, Soltes J. (2017). Quercetin attenuates the ischemia reperfusion induced COX-2 and MPO expression in the small intestine mucosa. Biomedical Pharmacotherapy. 95:246-254. https://www.ncbi.nlm.nih.gov/pubmed/28858733  

Quercetin is Included In:

Ultimate Gut Repair