Quercetin reduces markers of oxidative stress and inflammation in sarcoidosis.

BACKGROUND & AIMS Oxidative stress and low antioxidant levels are implicated in the aetiology of sarcoidosis, an inflammatory disease. Quercetin is a potent dietary antioxidant that also displays anti-inflammatory activities. Consequently, the aim is to examine the effect of quercetin supplementation on markers of oxidative stress and inflammation in sarcoidosis. METHODS A double-blind intervention study has been conducted with two groups of non-smoking, un-treated sarcoidosis patients, matched for age and gender. One group was given 4x500 mg quercetin (n = 12) orally within 24 h, the other one placebo (n = 6). Plasma malondialdehyde levels were used as marker of oxidative damage, plasma ratios of TNFα/IL-10 and IL-8/IL-10 as pro-inflammatory markers. RESULTS Quercetin supplementation improved the antioxidant defence, indicated by the increased total plasma antioxidant capacity. Moreover, quercetin supplementation also reduced markers of oxidative stress and inflammation in the blood of sarcoidosis patients. The effects of quercetin supplementation appeared to be more pronounced when the levels of the oxidative stress and inflammation markers were higher at baseline. CONCLUSIONS Sarcoidosis patients might benefit from the use of antioxidants, such as quercetin, to reduce the occurring oxidative stress as well as inflammation. The effects of long-term use of antioxidant supplementation in sarcoidosis, using e.g. quercetin, on improvement of lung function remain to be investigated. (www.clinicaltrials.gov; NCT-00402623).