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:
- citrus fruits
- red wine
- 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.
Preventing neurological diseases
Quercetin may help to prevent neurodegenerative diseases, such as Alzheimer's or Parkinson's disease.
Oxidative stress contributes to the development of neurodegenerative diseases. Oxidative stress occurs when there is an imbalance of free radicals in the body. The antioxidant properties of quercetin may help fight free radicals.
Research on rats showed that quercetin could protect against oxidative stress. It also showed quercetin could protect against the toxic effect of certain metals on the nervous system.
Some people reported minor side effects when taking high doses of quercetin, such as 1,000 mg per day, long-term.
Side effects may include:
- tingling sensations
Quercetin may interact with some medications, so people should ask their doctor before taking a supplement.
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.