Quercetin reduces illness but not immune perturbations after intensive exercise.
OBJECTIVE
To investigate the effects of quercetin supplementation on incidence of upper respiratory tract infections (URTI) and exercise-induced changes in immune function.


METHODS
Trained male cyclists (N=40) were randomized to quercetin (N=20) or placebo (N=20) groups and, under double-blind procedures, received 3 wk quercetin (1000 mg.d(-1)) or placebo before, during, and for 2 wk after a 3-d period in which subjects cycled for 3 h.d(-1) at approximately 57% Wmax. Blood and saliva samples were collected before and after each of the three exercise sessions and assayed for natural killer cell activity (NKCA), PHA-stimulated lymphocyte proliferation (PHA-LP), polymorphonuclear oxidative-burst activity (POBA), and salivary IgA output (sIgA).


RESULTS
Pre- to postexercise changes in NKCA, PHA-LP, POBA, and sIgA did not differ significantly between quercetin and placebo groups. URTI incidence during the 2-wk postexercise period differed significantly between groups (quercetin=1/20 vs placebo=9/20, Kaplan-Meier analysis statistic=8.31, P=0.004).


CONCLUSIONS
Quercetin versus placebo ingestion did not alter exercise-induced changes in several measures of immune function, but it significantly reduced URTI incidence in cyclists during the 2-wk period after intensified exercise.
Nieman
David C
DC
Department of Health, Leisure, and Exercise Science, Appalachian State University, Boone, NC 28608, USA. niemandc@appstate.edu
Henson
Dru A
DA
Gross
Sarah J
SJ
Jenkins
David P
DP
Davis
J Mark
JM
Murphy
E Angela
EA
Carmichael
Martin D
MD
Dumke
Charles L
CL
Utter
Alan C
AC
McAnulty
Steven R
SR
McAnulty
Lisa S
LS
Mayer
Eugene P
EP
D000328:Adult; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007107:Immune System / Q000187:drug effects* / Q000502:physiology; D007694:Killer Cells, Natural; D008297:Male; D009504:Neutrophils; D009195:Peroxidase / Q000097:blood; D005082:Physical Exertion / Q000502:physiology*; D011794:Quercetin / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D012141:Respiratory Tract Infections / Q000188:drug therapy*; D013601:T-Lymphocytes