Quercetin is part of a family of natural compounds called "flavonoids," found in fruits and vegetables as well as some flowers. Flavonoids have antioxidant properties, which means they go through the body and fight free radicals that damage healthy cells. Researchers from the Linus Pauling Institute at the University of Oregon state that the ability of a flavonoid to be an effective antioxidant depends upon its molecular structure, and that quercetin is one of the most powerful antioxidants because it has all of the necessary structural features. Quercetin is found in foods such as apples, citrus fruit, grapes, dark berries, onions, red wine and tea. It is also available as a dietary supplement, but relying on food sources of quercetin is recommended by the American Cancer Society because food also contains other necessary vitamins and minerals that work with quercetin to make it even more effective.
Quercetin has been found to be a powerful anti-inflammatory. Inflammation in the body leads to many health ailments and diseases. Arthritis is caused by inflammation between the joints. A report in the 2008 issue of the "Journal of Pre-Clinical and Clinical Research" (JPCCR) states that quercetin acts quickly within the body and can ease arthritis pain within two to three days. (The amount of quercetin in this study was 750 mg daily, provided through supplements.) A study in the July 2008 medical journal "Metabolism" verifies the JPCCR report that quercetin is an anti-inflammatory, stating that it is found to be effective in reducing signs of inflammation within the blood.
The American Academy of Family Physicians describes histamines as substances that irritate the cells in the body. This is why they cause sneezing, itching, and other allergy type reactions. An antihistamine prevents these symptoms by not allowing histamines to attach to and irritate the cells.
The University of Maryland Medical Center reports that, in test tube studies, quercetin is shown to prevent the release of histamines.
Quercetin has been found to both treat and prevent cancers. The June 11, 2009 issue of the "Journal of Experimental and Clinical Cancer Research" shows that quercetin is found to be protect against the formation of liver cancer cells, mainly due to its role as an antioxidant. Quercetin is also found to treat cancer by causing apoptosis, or "cell death," as reported in the May 18, 2009 edition of the medical journal, "Phytotherapy Research." While these studies are promising, most have been performed on mice and rats but not on humans. The American Cancer Society (ACS) reports a human study in which the combination of quercetin and curcumin supplements decrease the size and quantity of rectal tumors. The stand of the ACS is that they would like to see more clinical trials on the effects of quercetin on cancer in humans before recommending supplements. However, they do promote adding quercetin to the diet by increasing your daily intake of fresh fruit and vegetables.
Anti-Heart Disease Properties
Quercetin is known to have protective benefits when it comes to heart disease. The April 4, 2008 edition of the "Journal of Biological Chemistry" reports a study that shows the powerful action of quercetin against cardiovascular disease. In this study, they find that quercetin goes directly to the areas of the arteries that are injured or inflamed, while passing over healthy areas. The University of Maryland Medical Center also reports that quercetin may protect against the build up of plaque in the arteries and the LDL (bad) cholesterol damage.