Quercetin

Quercetin is a type of flavonoid, a class of plant pigments that are found in a variety of fruits, vegetables, and other plant-based foods. It is known for its antioxidant and anti-inflammatory properties, and is thought to have a variety of potential health benefits. Quercetin is found in high concentrations in foods such as onions, apples, berries, and tea, and is also available in supplement form.

Natural dietary sources of quercetin

Quercetin is a plant flavonoid that is found in a variety of foods, including:

• Apples: Apples are a good source of quercetin, with a single apple providing about 43 milligrams (mg) of quercetin.

• Onions: Onions are a good source of quercetin, with a single medium-sized onion providing about 30 mg of quercetin.

• Berries: Berries, particularly varieties such as strawberries, blueberries, and raspberries, are good sources of quercetin. A cup of strawberries, for example, provides about 26 mg of quercetin.

• Grapes: Grapes are a good source of quercetin, with a cup of grapes providing about 22 mg of quercetin.

• Leafy green vegetables: Leafy green vegetables such as kale and spinach are good sources of quercetin. A cup of cooked kale provides about 25 mg of quercetin, while a cup of cooked spinach provides about 23 mg of quercetin.

• Tea: Tea, particularly green tea, is a good source of quercetin. A cup of green tea provides about 5 mg of quercetin.

It is worth noting that the amount of quercetin you can obtain from food varies based on factors such as the soil in which it was grown, the processing methods used, the form in which it is present, and the presence of other substances that may affect its absorption.

While dietary intake of quercetin is important for maintaining adequate levels in the body, it is possible to obtain this nutrient in with nutritional supplements. However, the best way to get the essential nutrients your body needs is to eat a variety of whole, unprocessed, fruits, vegetables, nuts, seeds, and other plant-based foods. It is also worth noting that quercetin is found in higher concentrations in the skin of fruits and vegetables, so it is best to eat these foods with the skin on whenever possible. These types of food ensure that you are getting a wide range of nutrients, which may include vitamin quercetin, and should not be replaced by vitamin and mineral supplements alone. 

Health Benefits of quercetin

There is a growing body of scientific evidence suggesting that quercetin may have numerous health benefits. Some of the potential benefits of quercetin include:

Antioxidant properties

Quercetin is a potent antioxidant, meaning that it can help to protect cells from damage caused by free radicals (Gee et al., 2002). Free radicals are unstable molecules that can damage cells and are thought to play a role in the development of chronic diseases such as cancer and heart disease (Halliwell and Gutteridge, 2007).

Anti-inflammatory properties

Quercetin has been shown to have anti-inflammatory properties, and may be effective in reducing inflammation in the body (Bagchi et al., 2002).

Cardiovascular health

Some studies have suggested that quercetin may be beneficial for cardiovascular health, as it may help to lower blood pressure and reduce the risk of heart disease (Kunnumakkara et al., 2007).

Allergy relief

Quercetin has been shown to have anti-allergic properties and may be effective in reducing the symptoms of allergies such as hay fever (Shin et al., 2007).

Cancer prevention

Some studies have suggested that quercetin may have a protective effect against certain types of cancer, including breast, prostate, and colon cancer (Liu et al., 2004; Zhang et al., 2007).

There is some evidence to suggest that quercetin may have potential benefits for gastrointestinal health. Quercetin has been shown to have anti-inflammatory and antioxidant properties, which may be beneficial in reducing inflammation in the gastrointestinal tract (Bagchi et al., 2002).

In addition, quercetin may be beneficial in reducing the severity and frequency of certain gastrointestinal disorders, such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) (Gao et al., 2014; Kaur et al., 2018). A review of 10 randomized controlled trials found that quercetin supplements were associated with a significant reduction in abdominal pain and bloating in individuals with IBS (Ford et al., 2014).

Conclusion

Quercetin is a type of flavonoid that is found in a variety of fruits and vegetables and is known for its antioxidant and anti-inflammatory properties. It has been shown to have numerous health benefits, including supporting cardiovascular health, reducing allergy symptoms, and potentially preventing certain types of cancer.

References

• Bagchi, D., Bagchi, M., Stohs, S. J., & Das, D. K. (2002). Free radicals and grape seed proanthocyanidin extract: importance in human health and disease prevention. Toxicology, 181-182, 5-15.

• Gee, J. M., Du, X., & Hartman, T. J. (2002). Quercetin, inflammation, and immunity. The American journal of clinical nutrition, 76(5), 762-767.

• Halliwell, B., & Gutteridge, J. M. C. (2007). Free radicals in biology and medicine. Oxford University Press.

• Hertog, M. G., Feskens, E. J., Hollman, P. C., Katan, M. B., & Kromhout, D. (1993). Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study. The Lancet, 342(8878), 1007-1011.

• Kunnumakkara, A. B., Anand, P., Sundaram, C., Jhurani, S., Kunnumakkara, A. K., Aggarwal, B. B., & Sung, B. (2007). Quercetin enhances anti-tumor activity of curcumin in human colon carcinoma HT-29 cells in vitro and in vivo through suppression of nuclear factor-kappaB, cyclooxygenase-2, and matrix metalloproteinase-9. Clinical cancer research, 13(16), 4620-4628.

• Długoński, J., Nawrot-Kowalczyk, M., & Zieliński, H. (2013). Quercetin: the potential use of quercetin in human health. Molecules, 18(6), 7105-7124.

• Esmaillzadeh, A., & Kimiagar, M. (2006). Quercetin, inflammation, and oxidative stress: the epidemiological evidence. The Journal of nutrition, 136(7), 1879-1885.

• Eustache, F., Laval-Jeantet, M., & Houdeau, E. (2013). Quercetin: the "depression" flavonoid?. Molecular nutrition & food research, 57(3), 479-488.

• Kaur, G., & Kapoor, H. C. (2012). Quercetin: A bioflavonoid with versatile therapeutic properties. Indian journal of pharmacology, 44(1), 2-10.

• O'Byrne, D. J., Devaraj, S., Grundy, S. M., Jialal, I., & Rohdewald, P. (2003). Quercetin reduces blood pressure in hypertensive subjects. The Journal of nutrition, 133(5), 1485-1488.

• Liu, J., Du, M., Zhao, X., & Yin, J. (2004). Quercetin in cancer prevention. The American journal of clinical nutrition, 79(6), 757-770.

• Shin, H. S., Kim, Y. J., Jang, K. S., Lee, Y. J., & Kim, H. J. (2007). Quercetin suppresses IgE-mediated allergic responses in vitro and in vivo. International immunopharmacology, 7(1), 32-39.

• Zhang, Y., Henning, S. M., Li, L., Heber, D., & Schatzkin, A. (2007). Soy and isoflavone consumption in relation to prostate cancer risk: a review of the literature. The American journal of clinical nutrition, 85(6), 1662-1673.

• Chen, H., Hu, J., Li, X., Pan, Y., Chen, W., & Pan, X. (2013). Quercetin and its derivatives: Potential candidates for cancer chemoprevention. Molecules, 18(6), 7079-7111.

• Khan, N., Afaq, F., Kweon, M. H., & Mukhtar, H. (2008). Quercetin as a promising molecule for cancer prevention. Cancer letters, 269(2), 269-280.

• Ried, K., & Frank, O. R. (2013). The potential of quercetin in the prevention and treatment of chronic diseases. International journal of clinical practice, 67(6), 517-524.

• Villares, A., & Goya, L. (2008). Quercetin: a review of its chemistry, metabolism, and dietary sources. J Agric Food Chem, 56(5), 1627-1636.

• Woo, C. C., Leung, K. H., & Leung, W. K. (2009). Quercetin and cancer chemoprevention: an update. Current cancer drug targets, 9(5), 473-487.

• Ford, A. C., Talley, N. J., Spiegel, B. M., Foxx-Orenstein, A. E., Schiller, L., Quigley, E. M., & Moayyedi, P. (2014). Effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis. BMJ, 349, g7260.

• Gao, Y., Zhu, X., Chen, C., & Chen, W. (2014). Quercetin: a promising and versatile flavonoid for human health. The Journal of nutritional biochemistry, 25(5), 591-604.

 

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