Quercetin is one of the most common flavonoids, and is present in many foods. It also appears in red wine, black tea, and green tea. When you get your quercetin from fruits and vegetables, you reap the other benefits of those foods. You also increase your intake of fiber, which is lacking in the standard American diet.
Quercetin is available as a supplement, often with a recommended dose of 500-1,000 mg per day. It’s considered safe to use, but may interact with several medications, including antibiotics and blood thinners. Doses over one gram may damage the kidneys.
There’s no recommended daily allowance for quercetin, but these commonly eaten foods are good sources of it.