Quercetin Reduces Illness Rates But Not Immune Perturbations Following 3 Days Intensive Exercise In Cyclists

Abstract

PURPOSE: To investigate the effects of quercetin (Q) supplementation on incidence of upper respiratory tract infections (URTI) and exercise-induced changes in stress hormones and immune function. METHODS: Trained male cyclists (N=40) were randomized to Q (N=20) or placebo (P) (N=20) groups and under double blind procedures received 3 wks Q (1000 mg/day) or P prior to, during, and for 2 wks after a 3-d period in which subjects cycled for 3 h/ day at ∼57% Wattsmax. Blood and saliva samples were collected before and after the 3 sessions and assayed for natural killer cell activity (NKCA), PHA-induced lymphocyte proliferation (PHA-LP), granulocyte oxidative burst activity (GOBA), salivary IgA output (sIgA), and plasma cortisol and epinephrine. RESUITS: Pre-to-post-exercise changes inNKCA, PHA-LP, GOBA, sIgA, and plasma cortisol and epinephrine did not differ significantly between Q and P groups. URTI incidence during the 2-week post-exercise period differed significantly between groups (Q= 1/20 vs. P = 9/20, Chi-square = 8.53, P=0.0035). CONCLUSIONS: Q vs. P ingestion did not alter exercise-induced changes in plasma stress hormones and several measures of immune function, but significantly reduced URTI incidence in cyclists during the 2-week period following intensified exercise. Partially Supported by a grant from the Defense Advanced Research Projects Agency (DARPA) and the Army Research Office (ARO), award number W911NF-06-0014.