Quercetin is perhaps already known as the secret ingredient in so-called "superfoods" such as apples, blueberries, broccoli and tomatoes. This is also a colourful flavonoid found in brightly coloured fruit and vegetables. Quercetin also has a strong antioxidant and anti-inflammatory effect. A quercetin-rich diet is a possible reason why some people reach an old age and have anti-ageing properties. Sports supplements also often contain quercetin, assuming that it would increase endurance.