The exact cause of the chronic lung disease sarcoidosis is still unknown. Consequently, a complete efficacious treatment is still not available. Earlier studies indicate an important key role for oxidative stress, i.e. an imbalance between the production of and the protection against ROS, in the etiology of sarcoidosis. Antioxidants, needed for protection against ROS, are indeed lower in sarcoidosis. Therefore, antioxidant therapy to strengthen the reduced antioxidant defense might be efficacious in sarcoidosis treatment. Since ROS are also capable of initiating and mediating inflammation, antioxidant therapy might also mitigate the elevated inflammation that occurs in sarcoidosis. The flavonoid quercetin possesses both anti-oxidative and anti-inflammatory capacities and might therefore serve as a good candidate for antioxidant therapy in sarcoidosis.

Therefore, the aim of the present study is to determine the effect of quercetin supplementation in sarcoidosis patients on markers of both oxidative stress and inflammation.