The Incredible Properties of Quercetin

The Most Potent Flavonoid

Quercetin is one of the most biologically active flavonoids found in many fruits and vegetables. Flavonoids are phytonutrients that are responsible for providing rich colours, such as the blue in blueberries and the red in raspberries. Current research is revealing that quercetin is a very potent flavonoid with powerful antioxidant properties that give it both preventative and therapeutic value in many areas of health. Here are three of the most promising areas of research on quercetin:

1. Cancer prevention: As a powerful antioxidant, quercetin and other flavonoids, like resveratrol and catechins found in red wine and tea, have been shown to strengthen the immune system and inhibit the growth of cancer cells. Antioxidants fight against and “scavenge” free radicals, which are harmful particles in the body that damage cells. Quercetin has the ability to neutralize free radicals and reduce the damage that they cause. People who eat more fruits and vegetables that are high in flavonoid nutrients, tend to have lower cancer risk, especially cancers of the breast, colon, and prostate.

2. Supporting Cardiovascular health: Scientists have also long considered quercetin helpful in both preventing and treating other chronic diseases, such as heart disease, hypertension, insulin resistance, and LDL (“bad”) cholesterol. For instance, studies have found that quercetin may help reduce the risk of plaque buildup in arteries (“atherosclerosis”) and reduce the damage caused by LDL cholesterol that can lead to heart attacks and strokes. Studies have also shown that people who eat diets high in flavonoids like quercetin have lower risk of these cardiovascular diseases.

3. Anti-inflammatory properties: Quercetin has also been shown to be an effective nutrient for supporting respiratory health by reducing the inflammation caused by asthma and allergies—especially the symptoms caused by hay fever such as runny nose, watery eyes, and hives. Quercetin acts as an “antihistamine”, and prevents the release of histamines, which are the chemicals that cause allergic reactions. Quercetin’s anti-inflammatory effect has also been researched to provide relief for those who suffer from arthritis.

Dietary sources and Supplementation of Quercetin: Quercetin is found in most fruits and vegetables, particularly citrus fruits, apples, onions, asparagus, kale, tomatoes, and parsley. It is also possible to supplement with quercetin, which is often combined with vitamin C, grape seed, bilberry, ginkgo biloba, and green tea.  Although supplementing with quercetin is generally considered to be safe, large amounts can place stress on the liver and kidneys. Also, use caution with certain medications such as blood thinners and corticosteroids. It is always best to consult with a specialized health care practitioner for guidance.


Dr. Suzanne Bartolini is a Naturopathic Doctor at Hooper’s in Oakville and The Healing Source in Toronto. For more information, please visit:


Categories: Supplements, Neutraceuticals, & Herbs