Introduction ! Athletes participating in prolonged and intensive exercise such as marathon and ultramarathon race events experience acute physiological stress reflected by muscle microtrauma, oxidative stress, and systemic inflammation [27, 38,39]. Concomitant with these stressors are widespread perturbations in innate and adaptive immunity including decreases in natural killer (NK) cell cy- totoxic activity, granulocyte respiratory burst ac- tivity, nasal and salivary IgA (sIgA) secretion, delayed type hypersensitivity, and mitogen-in- duced lymphocyte proliferation, as well as exten- sive alterations in circulating immune cell popu- lations [2, 25, 29, 31]. This period of decreased host protection is often followed by elevated rates of upper respiratory tract infections in the athletes 1 – 2 weeks after competition. Efforts to link the immunological perturbations with in- creased infection risks have, however, been rela- tively unsuccessful [12,29]. Numerous attempts to counter the exercise-in- duced immune alterations using nutritional sup- plements have been explored. Supplements studied so far include carbohydrate beverages, zinc, omega-3 fatty acids, glutamine and various antioxidants such as vitamins C and E. Of these, carbohydrate ingestion has emerged as an effec- tive countermeasure against exercise-induced in- flammation, but has little effect on immune mea- sures such as lymphocyte function (T cells and NK cells), granulocyte oxidative burst activity and sIgA output [25, 26]. Flavonoids are a large and complex group of bio- active polyphenolic compounds that are abun- dant in the plant kingdom and so in the human diet. Their strong antioxidant activities have gen- erated much interest over the past 10 years with regard to their potential role in prevention of var- ious diseases associated with oxidative stress [18, 19,21]. These molecules are composed of two phenolic benzene rings linked to a heterocylic pyran or pyrone and are mostly present in the glycoside form with one or more sugar groups bound to the phenolic rings [18,19,21]. Quercetin (3,3¢,4¢,5,7-pentahydroxyflavone) is a common flavonol-type flavonoid that constitutes a signifi- Abstract ! This study measured the influence of the flavo- noid quercetin on immune changes and inci- dence rates of upper respiratory tract infections in ultramarathoners competing in the 160-km Western States Endurance Run. Sixty-three run- ners were randomized to quercetin and placebo groups, and under double-blinded methods in- gested 1000 mg/day quercetin for 3 wks before, during, and 2 wks after the race. Thirty-nine of the 63 subjects (n = 18 for quercetin, n = 21 for placebo) finished the race and provided blood and saliva samples the morning before the race and 15– 30 min postrace. Upper respiratory tract infections were assessed during the week before and the 2-wk period after the race using an ill- ness symptom checklist. Race times did not differ significantly between quercetin and placebo groups. Significant pre- to postrace decreases were measured for natural killer cells (43%), granulocyte respiratory burst activity (55%), and salivary IgA output (48%), and increases for neu- trophil (288%) and monocyte (211%) cell counts, with no significant group differences. Postrace illness rates did not differ between groups. In conclusion, quercetin supplementation for 3 wks before and 2 wks after the Western States Endur- ance Run had no effect on illness rates, perturba- tions in leukocyte subset counts, or decreases in granulocyte respiratory burst activity and sali- vary IgA. Post-160-km Race Illness Rates and Decreases in Granulocyte Respiratory Burst and Salivary IgA Output are Not Countered by Quercetin Ingestion Authors D. Henson 1 , D. Nieman 2 , J. M. Davis 3 , C. Dumke 2 , S. Gross 2 , A. Murphy 3 , M. Carmichael 3 , D. P. Jenkins 1 , J. Quindry 2 , S. McAnulty 2 , L. McAnulty 4 , A. Utter 2 , E. Mayer 3 Affiliations 1 Department of Biology, Appalachian State University, Boone, North Carolina, United States 2 Department of Health, Leisure, and Exercise Science, Appalachian State University, Boone, North Carolina, United States 3 Department of Exercise Science, University of South Carolina, Columbia, South Carolina, United States 4 Department of Family and Consumer Sciences, Appalachian State University, Boone, North Carolina, United States Key words l " exercise l " infections l " antibodies l " natural killer cells l " IgA l " respiratory burst accepted after revision November 15, 2007 Bibliography DOI 10.1055/s-2007-989424 Published online 2008 Int J Sports Med © Georg Thie- me Verlag KG Stuttgart • New York • ISSN 0172-4622 Correspondence Dr. Dru Henson Appalachian State University Department of Biology IG Greer 201, CAS Boone, North Carolina 28608 United States Phone: + 1 82 82 62 30 78 Fax: + 1 82 82 62 48 91 hensonda@appstate.edu Henson D et al. Quercetin, Immunity and … Int J Sports Med Immunology