Before jumping directly into benefits, we should know the basics about the compound. So, this article will help you to understand about the quercetin. Other than that, we will cover the benefits and risks associated with quercetin.
Quercetin and its Benefits - All You Need to Know
Quercetin is a flavonol that belongs to the group of plant compounds known as flavonoids. Flavonoids are phytochemical compounds found in plants, fruits, vegetables and grains. Humans cannot synthesise quercetin in their body but many fruits, vegetables and drinks contain it. Flavonoids such as quercetin, exhibit antioxidant properties. They have an ability to neutralise free radicals that can cause cell membrane damage which result in the cell death (1).
Benefits of Quercetin
Quercetin is a versatile molecule which possesses many pharmacological properties such as neurological, antioxidant, anticancer, antiviral, cardiovascular, antimicrobial, anti-inflammatory, hepatoprotective, protective of the reproductive system and anti-obesity agent. Other possible health benefits of quercetin are as follows:
1.Antioxidant properties of quercetin:
Quercetin is a powerful antioxidant. It helps to eliminate free radicals from the body. Free radicals are the molecules that contain unpaired electrons which make them unstable.They always try to pull electrons away from other molecules to get stable. This process can damage cells and DNA. So here, quercetin plays a major role. It cleans up free radicals by pairing with their single electrons so that they can no longer cause damage (2).
2.Antimicrobial and antiviral effects:
Quercetin has antiviral and antibacterial properties. Studies show that quercetin can inhibit the growth of many bacterial species i.e., Escherichia coli, Salmonella enterica and Listeria monocytogenes. It disrupts the integrity of bacterial cell membrane and thus, helps in inhibiting the bacterial growth (3).
Studies also revealed the antiviral effect of quercetin against human T-lymphotropic virus1 (cancer causing virus) and dengue virus type-2. It is able to inhibit the initial stage of viral infection as it has an ability to interact with protease (an enzyme responsible for viral replication). Thus, it helps to reduce the inflammation caused by infection (4).
3.Reducing the risk of cancer:
Cancer has been found in sixty different parts of the human body and requires new therapeutics for its treatment. Researchers reported that a diet with high flavonoid content can lower the risk of certain cancers and lower down the cancerous cell growth (5).
Inflammation is the natural response of the body to injury and stress that usually helps the body to heal. However, chronic inflammation can harm the body and contribute to specific health conditions. Quercetin can help stabilise the cells that release histamine in the body and thereby have an anti-inflammatory and antihistamine effect. A study of women with rheumatoid arthritis found that taking quercetin helped reduce their pain and stiffness (6).
5.Benefitting neurological health
Quercetin may reduce the risk of neurodegenerative diseases, such as Parkinson’s and Alzheimer’s disease. Oxidative stress contributes to the development of neurodegenerative diseases. Oxidative stress takes place when there is an imbalance of free radicals in the body. The antioxidant properties of quercetin may help fight free radicals. A study showed that when mice with Alzheimer’s were given quercetin injections over a three-month period, it reversed some of the disease’s markers and the mice performed better on learning tests (7).
6.Lowering the risk of heart disease and blood pressure
Diet contributes an important role in reducing the risk of cardiovascular diseases i.e., strokes and heart diseases. As vegetables and fruits contain flavonoids, eating them more may help reduce the risk of these diseases. Studies revealed that certain flavonoids, including quercetin, might lower your risk for plaque build-up in your arteries that could cause stroke or heart attack (8).
A study revealed that taking quercetin supplements could be an effective way to reduce blood pressure. From the study, it was concluded that people who were overweight and took a quercetin supplement of 150 mg per day had reduced levels of harmful cholesterol in their blood and reduced systolic blood pressure. (Systolic blood pressure measures the pressure in the blood vessels during a heartbeat) (9).
People can get quercetin through their diet by eating a range of vegetables and fruit daily. Onions are the richest sources of dietary flavonoids one can get and provide 28.4-48.6 milligrams (mg) of quercetin per 100g.
“If you are someone who doesn't like fruits or vegetables or finds it boring to eat them consistently, then you may be a good candidate for taking a quercetin supplement”!
Quercetin is available as a nutraceutical, in an appropriate dose of 100-500 mg daily. Bromelain and vitamin C are other substances which can also be taken as a supplement and they may help the body absorb quercetin more efficiently (10).
Side effects and risk associated with quercetin
Quercetin is naturally present in many fruits and vegetables and is safe to consume. As a supplement, it is safe with less or no side effects. In some instances, intake of more than 1,000 mg of quercetin per day may cause mild symptoms like stomach ache, headache and tingling sensations. Quercetin is safe for pregnant and breastfeeding women when consumed in food. However, there are no proper studies on the safety of quercetin supplements for pregnant and breastfeeding ladies. Hence, it should be avoided if you are pregnant/nursing (11).
Quercetin is a flavonoid with antioxidant properties. The capability of quercetin is claimed to exert various advantageous effects on health, which include fortification against various illnesses i.e., lung cancer, osteoporosis and cardiovascular disease. The studies exhibited that there has been a reduction in the risk of cardiovascular disease in subjects, who had a high consumption of flavonoids. Flavonol is the most prominent flavonoids in vegetables and fruits and of these, quercetin is the most commonly consumed in the human diet.
- Maalik, A., Khan, F. A., Mumtaz, A., Mehmood, A., Azhar, S., Atif, M., & Tariq, I. (2014). Pharmacological applications of quercetin and its derivatives: a short review. Tropical Journal of Pharmaceutical Research, 13(9), 1561-1566.
- Begum, A. N., & Terao, J. (2002). Protective effect of quercetin against cigarette tar extract-induced impairment of erythrocyte deformability. The Journal of nutritional biochemistry, 13(5), 265-272.
- Bozic, M., Gorgieva, S., & Kokol, V. (2012). Homogeneous and heterogeneous methods for laccase-mediated functionalization of chitosan by tannic acid and quercetin. Carbohydrate polymers, 89(3), 854-864.
- Zandi, K., Teoh, B. T., Sam, S. S., Wong, P. F., Mustafa, M. R., & AbuBakar, S. (2011). Antiviral activity of four types of bioflavonoid against dengue virus type-2. Virology journal, 8(1), 1-11.
- Dajas, F. (2012). Life or death: neuroprotective and anticancer effects of quercetin. Journal of ethnopharmacology, 143(2), 383-396.
- 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.
- Sabogal-Guaqueta, A. M., Munoz-Manco, J. I., Ramírez-Pineda, J. R., Lamprea-Rodriguez, M., Osorio, E., & Cardona-Gomez, G. P. (2015). The flavonoid quercetin ameliorates Alzheimer's disease pathology and protects cognitive and emotional function in aged triple transgenic Alzheimer's disease model mice. Neuropharmacology, 93, 134-145.
- Ciumarnean, L., Milaciu, M. V., Runcan, O., Vesa, Ș. C., Răchișan, A. L., Negrean, V., ... & Dogaru, G. (2020). The effects of flavonoids in cardiovascular diseases. Molecules, 25(18), 4320.
- Tamtaji, O. R., Milajerdi, A., Dadgostar, E., Kolahdooz, F., Chamani, M., Amirani, E., ... & Asemi, Z. (2019). The effects of quercetin supplementation on blood pressures and endothelial function among patients with metabolic syndrome and related disorders: A systematic review and meta-analysis of randomized controlled trials. Current Pharmaceutical Design, 25(12), 1372-1384.
- Mitchell, A. E., Hong, Y. J., Koh, E., Barrett, D. M., Bryant, D. E., Denison, R. F., & Kaffka, S. (2007). Ten-year comparison of the influence of organic and conventional crop management practices on the content of flavonoids in tomatoes. Journal of agricultural and food chemistry, 55(15), 6154-6159.
- Andres, S., Pevny, S., Ziegenhagen, R., Bakhiya, N., Schafer, B., Hirsch‐Ernst, K. I., & Lampen, A. (2018). Safety aspects of the use of quercetin as a dietary supplement. Molecular nutrition & food research, 62(1), 1700447.
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