The Protective Effects of a Polyphenol-Enriched Protein Powder on Exercise-Induced Susceptibility to Virus Infection Maryam Ahmed, 1 * Dru A. Henson, 1 Matthew C. Sanderson, 1 David C. Nieman, 2 Nicholas D. Gillitt 3 and Mary Ann Lila 4 1 Department of Biology, Appalachian State University, Boone, NC 28608, USA 2 Human Performance Laboratory, Appalachian State University, North Carolina Research Campus, Kannapolis, NC 28081, USA 3 Dole Nutrition Research Laboratory, North Carolina Research Campus, Kannapolis, NC, 28081, USA 4 Plants for Human Health Institute, North Carolina State University, North Carolina Research Campus, Kannapolis, NC 28081, USA Prolonged and intensive exercise induces transient immunosuppression and is associated with an increased risk and severity of infections. The goal of this study was to characterize the antiviral and antibacterial properties of the bioactive metabolites of a blueberry–green tea-polyphenol soy protein complex (PSPC) in the serum of sup- plemented subjects during a 3-day intensified training period. Long-distance runners, randomly divided into two groups, ingested 40 g/day PSPC or placebo (soy protein and colorings) for 17 days, with a 3-day running period inserted at day 14. Blood serum samples were collected pre-14 days and post-14 days supplementation, and immediately and 14 h after the third day of running. The post-exercise serum from both groups significantly pro- moted the growth of Escherichia coli and Staphylococcus aureus in culture by 20–70%, but returned to normal levels following recovery. Furthermore, the serum from subjects ingesting PSPC did not display antibacterial properties at any time point. In contrast, there was a significant difference in the ability of serum from PSPC- supplemented versus placebo-supplemented athletes to protect cells in culture from killing by vesicular stomatitis virus following strenuous exercise. In addition, the serum of subjects who ingested PSPC significantly delayed an exercise-induced increase in virus replication. These results indicate that polyphenol complexes containing blueberry and green tea have the potential to protect athletes from virus infections following rigorous exercise. Copyright © 2014 John Wiley & Sons, Ltd. Keywords: virus infection; polyphenols; green tea; blueberry extract. INTRODUCTION Polyphenols are abundant micronutrients in our diet and are widespread constituents of fruits, vegetables, cereals, chocolates and beverages such as tea, coffee, beer and wine. Numerous studies have revealed that polyphenols exert beneficial effects on human health, including antioxidant, anti-inflammatory and anti-cancer activity (Gonzalez-Vallinas et al., 2013; Khurana et al., 2013; Landete, 2012). Furthermore, polyphenols derived from various sources have been reported to exert activity against a variety of infectious organisms such as respira- tory, sexually transmitted and food-borne viruses, and pathogenic bacterial strains (Andrae-Marobela et al., 2013; Daglia, 2012; Fioravanti et al., 2012; Li et al., 2013). However, much of the evidence on the prevention of diseases and infections by polyphenols is derived from in vitro or animal studies that are often performed with doses much higher than those available to humans. Fur- thermore, polyphenols are extensively metabolized by intestinal and hepatic enzymes and by the intestinal mi- croflora to generate circulating conjugated derivatives that are made available to target tissues (Del Rio et al., 2013). Therefore, in vitro studies with polyphenolic extracts may fail to accurately evaluate the effects of the various derivatives in humans. The goal of the current study was to determine whether the serum of subjects ingesting a high-dose polyphenol supplement would provide protective activity against viral and bacterial infections following a 3-day intensified train- ing regimen. During strenuous exercise, there is a dramatic increase in reactive oxygen species production resulting in oxidative stress (Powers and Jackson, 2008). Exhaustive exercise also induces structural damage to muscle cells, inflammation and immune dysfunction. Transient immu- nosuppression induced by prolonged, intense exercise is reported to increase the risk of acquiring respiratory tract infections in humans (Martin et al., 2009; Nieman, 1994). Therefore, there is great interest in evaluating the anti-microbial effects of polyphenols during strenu- ous exercise-induced immune dysfunction in humans. A number of epidemiological studies have attempted to determine the effects of specific intensities and dura- tions of exercise on the incidence of upper respiratory tract infections in humans (Ekblom et al., 2006; Nieman et al., 1989; Nieman et al., 1990). However, because of ethical constraints, there are limited studies that have evaluated whether polyphenolic compounds exert pro- tective effects against infectious organisms during stren- uous exercise in humans. We have developed in vitro assays to evaluate the antiviral and antibacterial activity in the serum of individuals supplemented with a blue- berry and green tea-polyphenol-rich soy protein-based * Correspondence to: Maryam Ahmed, Department of Biology, Appalachian State University, Boone, NC 28608, USA. E-mail: ahmedm@appstate.edu PHYTOTHERAPY RESEARCH Phytother. Res. (2014) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ptr.5208 Copyright © 2014 John Wiley & Sons, Ltd. Received 14 May 2014 Revised 03 July 2014 Accepted 07 July 2014