Quercetin is a pigment found in many plants, fruits, and vegetables. It may have some health benefits and help prevent a range of conditions. People can get quercetin through a balanced diet or by taking a supplement. Quercetin is a flavonol, which is a sub-category of flavonoids. Flavonoids are a particular chemical in plants, called phytonutrients, and have a wide range of health benefits. Humans cannot make quercetin in their body, but many fruits, vegetables, and drinks contain it. Foods and drinks that contain quercetin include: grapes, berries, cherries, apples, citrus fruits, onions, buckwheat, broccoli, kale, tomatoes, red wine and black tea.
Quercetin is also present in herbal remedies, such as ginkgo biloba and St John's wort. People can also take quercetin as a supplement. Quercetin is a more powerful antioxidant than vitamin C, vitamin E, or beta carotene. Quercetin might help reduce inflammation. One study on animals found that quercetin prevented both acute and chronic inflammation, in addition to showing anti-arthritis properties. Quercetin may contain anticancer properties that might help prevent the spread of cancerous cells and tumor growth. Quercetin may help to prevent neurodegenerative diseases, such as Alzheimer's or Parkinson’s disease.
Research suggests that quercetin might be an effective antihistamine, as it restricts histamine from being released from cells. These anti-allergy properties indicate that quercetin might help treat bronchitis and asthma. Quercetin has antibacterial properties, which are effective against almost all types of bacteria. Quercetin may improve blood vessel cell health and blood flow through arteries in people with heart disease. According to a 2016 study by the American Heart and Stroke Association, taking quercetin supplements could be an effective way to reduce blood pressure.
People can get quercetin through their diet by eating a range of fruit and vegetables each day. Onions have the highest level of quercetin compared to other tested produce, containing approximately 300 mg per kilogram.
If people take quercetin as a supplement, the most common dose is 500 mg per day, but some people can take up to 1,000 mg per day. Supplements may also include other substances, such as bromelain or vitamin C, which may help the body absorb quercetin more effectively.
Quercetin is actually part of the vitamin C complex. Ascorbic acid acts as an antioxidant ‘wrapper’ surrounding quercetin, other bioflavonoids, taurine and copper. The sum of all these organically bound chemicals is the vitamin C complex found in food. This is why it is so important to supplement a whole food vitamin C product in lieu of ascorbic acid.
Clinically, I use quercetin to facilitate the removal of histamine and/or cortisol from the bloodstream through phase II liver detoxification in the liver. This is frequently needed after rebuilding a patient’s adrenal glands. High residuals of cortisol will mimic adrenal stress disorder despite adequate herbal support with adaptogens.
Quercetin is a part of the vitamin C complex that can be useful in treating adrenal issues. However, it’s best taken in its whole food form with ascorbic acid or in food for daily consumption.
Source: January 14, 2019 NIH