The effect of quercetin on exercise induced cytokine response in trained cyclists
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Quercetin is a flavonoid found in commonly consumed fruits and vegetables that has exhibited powerful antioxidant and anti-inflammatory properties in rodents and in vitro. In humans, the effect of quercetin on exercise induced oxidative stress and inflammation is still equivocal and need to be further investigated. A powerful antioxidant such as quercetin may inhibit the high levels of oxidative stress and inflammation associated with the high volume and intensity of exercise training seen with endurance-trained individuals. PURPOSE: To determine the effect of 28 days of daily quercetin supplementation on intensive endurance exercise induced cytokine response. vi METHODS: Thirteen trained cyclists (VO2peak 58.8 ± 3.9 ml/kg/min) were recruited for this study from the University of Texas at Austin and the local Austin, Texas community and participated in this placebo controlled, randomized, crossover designed study. After initial assessment of baseline data (VO2peak, lactate threshold, and two familiarization time trials), participants began daily supplementation with either an antioxidant supplement containing vitamins and quercetin (Q-VIT: 1000mg quercetin, 820mg Vitamin C, 40mg Vitamin B3) or the same vitamin supplement without quercetin (VIT: 820mg Vitamin C, 40mg Vitamin B3). A simulated time trial using an electromagnetically braked cycle ergometer in which subjects had to complete a set amount of work (kJ) as fast as possible was performed on the last day of supplementation. Blood collection was performed at three time points of the time trial days: before exercise (PRE), after warm up (MIN 20), and immediately after time trial exercise (POST). Measured plasma markers were Interleukin-6 (IL-6), C-Reactive Protein (CRP), and Interleukin-10 (IL-10). RESULTS: Q-VIT compared to VIT had no effect on pre, min 20 and post exercise plasma IL-6, CRP, and IL-10 ( P= 0.7, 0.08, and 0.32 respectively). However there was a trend that Q-VIT lowered plasma CRP compare to VIT ( P = 0.08). CONCLUSION: Chronic supplementation for 28 days with a quercetin based antioxidant supplement did not affect plasma cytokine before during or after exercise. The results of the current study suggest that chronic supplementation with quercetin does not influence plasma cytokine and exercise induced cytokine response in endurance-trained athletes.