With links to a wide range of potential health benefits, quercetin is gaining ground as a compound people want to include in their diets. Like lycopene, resverotrol and antioxidant vitamins, quercetin can be acquired as a dietary supplement or obtained through food sources. As with most plant-derived compounds, getting quercetin through the foods you eat is cheaper, easier and more effective than taking unproven supplements.
Quercetin Defined
Quercetin is a type of phytochemical, a compound derived from plants that may have an effect on the body when consumed. Quercetin belongs to the group of phytochemicals called flavonols, which are part of the larger group, flavonoids. Other flavonols include kaempferol, myricetin and isorhamnetin. Like all flavonoids, quercetin has strong antioxidant properties.
Foods with Quercetin
Apples are a major source of quercetin. Other fruits containing quercetin include cherries, raspberries, blueberries, blackberries, red grapes and citrus fruits. Tomatoes, onion, kale, leek and broccoli are other sources. Beverages such as red wine and green or black tea also contain quercetin. Other sources include the edible garnish parsley, capers and leafy green vegetables. Organically grown tomatoes contain 79 percent more quercetin than those grown conventionally, according to a 2007 study published in the "Journal of Agricultural and Food Chemistry."
Potential Health Benefits
A 2002 study in the "American Journal of Clinical Nutrition" found that high levels of quercetin intake was linked to lower rates of lung cancer, type 2 diabetes, asthma and mortality from ischemic heart disease. Quercetin also acts as an antihistamine in laboratory studies, which may translate to activity against allergies and hay fever. Quercetin may also lower LDL cholesterol and blood pressure and reduce the symptoms of rheumatoid arthritis, interstitial cystitis and prostatitis. Other activity of quercetin may be linked to its antioxidant abilities, since antioxidants prevent cellular damage by neutralizing dangerous free radicals within cells.
Considerations
More research remains to be done on quercetin, since few clinical trials have been carried out using this flavonoid. One problem with studying this compound is that, like all phytochemicals, it is difficult to isolate the effects of quercetin from other compounds found in a given food. Quercetin probably works in synergy with other phytochemicals and some of its biological activity may only occur when it is found alongside these other biochemicals in food, not when it is taken as an isolated supplement.
References
- Linus Pauling Institute: Flavonoids
- University of Maryland Medical Center: Quercetin
- U.C. Berkeley Wellness Letter: Quercetin
- "American Journal of Clinical Nutrition": Flavonoid intake and risk of chronic diseases. P Knekt, et al. Sept. 2002
- "Journal of Agricultural and Food Chemistry": Ten-Year Comparison of the Influence of Organic and Conventional Crop Management Practices on the Content of Flavonoids in Tomatoes. Alyson E. Mitchell, et al. June 2007.
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