Quercetin Ingestion Does Not Alter Cytokine Changes In Athletes Competing in the Western States Endurance Run

Abstract

PURPOSE: To measure the influence of the antioxidant flavonol molecule, quercetin (Q), on plasma cytokines, leukocyte cytokine mRNA, plasma cortisol, muscle damage, C-reactive protein (CRP), and delayed onset of muscle soreness (DOMS) in ultra-marathoners competing in the 160-km Western States Endurance Run (WSER). METHODS: Sixty-three runners were randomized to Q and placebo (P) groups, and under double blinded methods ingested 1000 mg/day Q for 3 wks before, during, and 2 wks after the WSER. Thirty-nine of the 63 subjects (N=18 for Q, N=21 for P) finished the race, provided blood samples the morning before the race and 15–30 min post-race, and recorded DOMS during the week after the race using a 10-point Likert scale. RESULTS: Significant pre-to-post WSER increases were measured for 10 pro- and anti-inflammatory plasma cytokines, cortisol (Q=94%, P=96%), serum CRP (absolute increase, Q=318 and P=381 mg/L), and creatine kinase (CK) (absolute increase, Q=21574 and P=19472 U/L), with no significant group differences. DOMS peaked the day after the WSER (6.8±0.4 and 7.3±0.4 for Q and P, respectively, P=0.377) with no group differences seen during the 7-day post-WSER period. IL-6 mRNA did not change post-WSER, with a decrease measured for leukocyte IL-8 mRNA (0.21 and 0.25 fold change from rest, Q and P respectively), and increases for IL-1ra and IL-10 mRNA (12.9 and 17.2 fold change, respectively), with no significant group differences. CONCLUSION: Q supplementation for 3 wks before and 2 wks after the WSER had no effect on increases in plasma levels for 10 cytokines, cortisol, serum CRP, changes in leukocyte mRNAfor IL-8, IL-1ra, IL-10, and IL-6, muscle damage, and DOMS.