Quercetin 101: Nutrition and Its Health Benefits

One important component of plant-based foods such as fruits and vegetables are flavonoids. Flavonoids or bioflavonoids are compounds that give color to most plants and became popular due to their antioxidant properties¹.

They scavenge and neutralize free radicals that cause cell damage, illness, and aging². Quercetin, in particular, is a flavonoid considered as a superfood due to its potential benefit in improving cardiovascular health and even reducing the risk of cancer. So what exactly is quercetin? Keep reading to learn more about this amazing phytonutrient.

What is Quercetin?

Quercetin is one of the most common and well-studied flavonoid compounds. Basically, if you consume a lot of organic foods that sprout from the earth, you’ll get a lot of quercetin.

According to experts, quercetin is a powerful antioxidant providing anti-inflammatory, antihistamine, and antiviral properties, as well as serving the ability to reduce blood clots and oxidative stress in arteries³.

Quercetin - Health Benefits

It may help reduce the risk of heart disease

Studies suggest that quercetin can help support heart health by reducing blood vessel dysfunction, mitigating endothelial dysfunction, and reducing heart disease risk factors.⁴ This cardioprotective claim was backed up by one review by the European Journal of Medicinal Chemistry⁵.

In addition, a study of the Journal of the American Heart Association found that supplementation of 500 mg of quercetin per day significantly decreased blood pressure especially among people with diabetes⁶.

It may help lower blood sugar levels

It was found that quercetin acts on multiple targets of diabetes and regulates key signaling pathways which improves the symptoms as well as the complications of type 2 diabetes⁷.

It may help reduce inflammation

Several studies have found that supplementing with about 500 mg of quercetin per day helps lower levels of the inflammatory biomarker C-Reactive Protein (CRP), which is elevated in conditions like heart disease, rheumatoid arthritis, metabolic syndrome, and diabetes⁸.

In another study on 50 women with rheumatoid arthritis, it was found that the same amount of daily quercetin supplementation for eight weeks helped reduce morning stiffness and pain⁹.

It may boost cognitive function and support neurological health

A lot of studies have supported quercetin as a compound that offers neuroprotective benefits, due to its ability to defend the brain against oxidative stress and inflammation, leading to potentially lower risk for neurological conditions like Alzheimer’s Disease (AD) and dementia^10-11.

It may support longevity

A prospective non-randomized clinical study of 20-25 patients showed that supplementation of quercetin together with dasatinib slows cell proliferation and decelerates aging and the risk of age-related diseases¹².

Dietary Sources of Quercetin

Quercetin is present in many healthy foods, with onions having the highest quercetin content¹³.

Here is a detailed list of quercetin-rich foods and their corresponding quercetin content:^14-15.

Quercetin - Supplementation

As a supplement, quercetin appears to be generally safe with little to no side effects. Typical dosage ranges from 500–1,000 mg per day¹⁶.

Quercetin has a low bioavailability – meaning it is not efficiently absorbed by the body. However, studies have shown that combining it with other flavonoids or nutrients can help support its absorption¹⁷. That is why most quercetin supplements also include other substances such as bromelain or Vitamin C in order to maximize its absorption by the body.

In addition, quercetin is a lipophilic compound, aka lipid-loving molecules, thus dietary fat enhances its bioavailability. Nondigestible fiber may also improve quercetin bioavailability¹⁸. With that, quercetin supplementation is highly effective if taken after a meal¹⁹.

Final Words

Quercetin provides numerous health benefits– from reducing risks of certain diseases up to supporting longevity– thus it is great for overall health and wellness.

References:

1. 1. Quercetin. (n.d.). Retrieved January 31, 2023, from Mount Sinai Health System Website: https: //www.mountsinai.org/health-library/supplement/quercetin.
2. 2. Free radicals: How do they affect the body? (2017, July 29). Retrieved January 31, 2023, from Medicalnewstoday.com website: https://www.medicalnewstoday.com/articles/318652.
3. 3. Women’s Health. (2020, October 19). This is the immune-supporting antioxidant you’re about to see everywhere. Retrieved February 1, 2023, from mindbodygreen website: https: //www.mindbodygreen.com/articles/what-is-quercetin.
4. 4. Dagher, O., Mury, P., Thorin-Trescases, N., Noly, P. E., Thorin, E., & Carrier, M. (2021). Therapeutic Potential of Quercetin to Alleviate Endothelial Dysfunction in Age-Related Cardiovascular Diseases. Frontiers in cardiovascular medicine, 8, 658400. https://doi.org/10.3389/fcvm.2021.658400.
5. 5. Patel RV, Mistry BM, Shinde SK, et al. Therapeutic Potential of Quercetin as a Cardiovascular Agent. European Journal of Medicinal Chemistry. July 2018.
6. 6. Serban, M.-C., Sahebkar, A., Zanchetti, A., Mikhailidis, D. P., Howard, G., Antal, D., ... Lipid and Blood Pressure Meta-analysis Collaboration (LBPMC) Group. (2016). Effects of quercetin on blood pressure: A systematic review and meta-analysis of randomized controlled trials. Journal of the American Heart Association, 5(7). doi:10.1161/JAHA.115.002713.
7. 7. Dhanya, R. (2022). Quercetin for managing type 2 diabetes and its complications, an insight into multitarget therapy. Biomedecine & Pharmacotherapie [Biomedicine & Pharmacotherapy], 146(112560), 112560. doi:10.1016/j.biopha.2021.112560.
8. 8. Mohammadi-Sartang, M., Mazloom, Z., Sherafatmanesh, S., Ghorbani, M., & Firoozi, D. (2017). Effects of supplementation with quercetin on plasma C-reactive protein concentrations: a systematic review and meta-analysis of randomized controlled trials. European journal of clinical nutrition, 71(9), 1033–1039. https://doi.org/10.1038/ejcn.2017.55.
9. 9. Javadi, F., Ahmadzadeh, A., Eghtesadi, S., Aryaeian, N., Zabihiyeganeh, M., Rahimi Foroushani, A., & Jazayeri, S. (2017). The Effect of Quercetin on Inflammatory Factors and Clinical Symptoms in Women with Rheumatoid Arthritis: A Double-Blind, Randomized Controlled Trial. Journal of the American College of Nutrition, 36(1), 9–15. https://doi.org/10.1080/07315724.2016.1140093.
10. 10. Elumalai, P., & Lakshmi, S. (2016). Role of Quercetin Benefits in Neurodegeneration. Advances in neurobiology, 12, 229–245. https://doi.org/10.1007/978-3-319-28383-8_12.
11. 11. Khan, H., Ullah, H., Aschner, M., Cheang, W. S., & Akkol, E. K. (2019). Neuroprotective Effects of Quercetin in Alzheimer's Disease. Biomolecules, 10(1), 59. https://doi.org/10.3390/biom10010059.
12. 12. Lee, E. (2022). The Safety and Effectiveness of Quercetin and Dasatinib on the Epigenetic Aging Rates in Healthy Individuals. National Library of Medicine. Retrieved from https://clinicaltrials.gov/ct2/show/study/NCT04946383.
13. 13. G. Mohan Shankar, Jayesh Antony, Ruby John Anto. (2015). The Enzymes. doi:10.1016/bs.enz.2015.05.001.
14. 14. Haytowitz, P. by D., Wu, X., & Bhagwat, S. (2018, March). USDA Database for the Flavonoid Content of Selected Foods. Retrieved February 7, 2023, from Usda.gov website: https://www.ars.usda.gov/ARSUserFiles/80400535/Data/Flav/Flav3.3.pdf.
15. 15. Dabeek, W. M., & Marra, M. V. (2019). Dietary Quercetin and Kaempferol: Bioavailability and Potential Cardiovascular-Related Bioactivity in Humans. Nutrients, 11(10), 2288. https://doi.org/10.3390/nu11102288.
16. 16. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury [Internet]. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases; 2012-. Quercetin. [Updated 2020 Mar 28]. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK556474/.
17. 17. National Center for Biotechnology Information (2023). PubChem Compound Summary for CID 5280343, Quercetin. Retrieved February 7, 2023 from https://pubchem.ncbi.nlm.nih.gov/compound/Quercetin.
18. 18. Kaşıkcı M. B, Bağdatlıoğlu N. Bioavailability of Quercetin. Curr Res Nutr Food Sci 2016;4(Special Issue Confernce October 2016). http://dx.doi.org/10.12944/CRNFSJ.4.Special-Issue-October.20
19. 19. John-Baptiste, K. (2022, June 6). When to take Quercetin, Berberine and TMG. Retrieved February 7, 2023, from NMNBIO website: https://nmnbio.co.uk/blogs/news/when-to-take-quercetin-berberine-and-tmg