The antioxidant activity of quercetin, especially when combined with another antioxidant, vitamin C, bolsters the body’s immune defences and provides a way to protect against cancer. It also helps prevent the free radical damage to cholesterol that promotes heart disease. It is also known to have iron-chelating and iron-stabilising properties.
Quercetin also helps the body defend itself against harmful micro-organisms and can improve the tissue health of the intestinal wall which can help when there is an overgrowth of the Helicobacter pylori bacteria in the intestines. It also has powerful antibacterial properties against the Escherichia coli bacteria.
Quercetin has also shown in studies to be a powerful antiviral substance against the herpes, influenza, mengo, polio, pseudorabies and rabies viruses.
Natural sources of quercetin in alphabetical order
- Apples
- Apricots
- All spice
- Capers
- Bilberries
- Blackberries
- Blueberries
- Buckwheat
- Cherries
- Chia seeds
- Chokeberries
- Citrus fruits
- Grapes (black)
- Green tea
- Fennel seeds
- Leafy green vegetables
- Legumes
- Liquorice root
- Maqui berry
- Olive oil
- Parsley
- Phyllanthus
- Onions (red)
- Scutellaria root
- Thyme
- Wine
NOTE: Cooking reduces the quercetin levels in foods.
Related subjects
- A-Z of nutrients
- Bacterial infections
- Cancer
- Immune system disorders
- Influenza
- Heart disorders
- Herpes
- Stomach ulcers
- Virus infections
- Vitamin C