Quercetin Boosts Immunity and Helps Maintain Mental Performance

Reading time: 3 – 4 minutes

In February 2007, researchers at Appalachian State University announced the results of a clinical study on the flavonoid quercetin at the Southeastern Regional Meeting of the American College of Sports Medicine, held in Charlotte, N.C. Their results showed that quercetin may help reduce illness and maintain mental performance in physcially stressed test subjects. I’ve written about the antioxidant quercetin in a previous article as an alternative to dichloroacetate (DCA), a chemotherapeutic agent that was recently shown to selectively inhibit cancer cell growth in lung, breast and brain tumor cells grown in culture and lung tumors grown in immunocompromisted rats.

In December 2005, the Defense Advanced Research Projects Agency (DARPA) awarded Appalachian State University 1.1 million to fund a two-year study of the effects of quercetin [1]. DARPA is seeking ways to maintain troop immune systems during times of physical and cognitive stress. Dr. David Nieman is the principal investigator of the study and a professor in the Department of Health, Leisure and Exercise Science at Appalachian State University. He has been investigating the influence of exercise and nutrition on the immmune system for the last 23 years.

The double-blind, randomized, placebo-controlled study provided 1,000 mg/day of high-purity quercetin, a polyphenol, plus niacin and vitamin C to aid in absorption, to 20 trained cyclists for five weeks. A second group of 20 cyclists received a placebo. Three weeks into the study, participants rode a bicycle to the point of exhaustion three hours per day for three days. Blood and tissue samples were collected and analyzed to track any physicological changes that occurred.

Only 5% of the group that received quercetin reported illness after being physically stressed, compared with 45% of the participants who received placebo. No adverse side effects were observed. Surprisingly, the immune-boosting properties of quercetin weren’t readily observable until after the three-day intense exercise period. Additionally, when given an alertness test, those participants that were given quercetin better maintained their ability to react after exhaustion.

Said Dr. Nieman [2]:

It appears that it takes significant stress to bring out quercetin’s infection-fighting properties. This all happened when athletes were under high oxidative stress, when stress hormones were high, and they were also undergoing muscle damage.

Nieman plans a follow-up study to see if quercetin has any benefits for people who are undergoing everyday mental stress.

More about quercetin can be found in these posts:


  1. Defense Dept Funds $1.1 Million for Research. The College of Fine & Applied Arts, Appalicain State University. 2005 Dec 7.
  2. Research at Appalachian State Indicates Natural Plant Substance Helps Reduce Illness in Physically Stressed Athletes; Findings May Have Military Application. Appalachian State University News. 2007 Feb 8.
  3. Sampson et al. Flavonol and flavone intakes in US health professionals. J Am Diet Assoc. 2002 Oct;102(10):1414-20.
    View abstract
About the Author

Walter Jessen, Ph.D. is a Data Scientist, Digital Biologist, and Knowledge Engineer. His primary focus is to build and support expert systems, including AI (artificial intelligence) and user-generated platforms, and to identify and develop methods to capture, organize, integrate, and make accessible company knowledge. His research interests include disease biology modeling and biomarker identification. He is also a Principal at Highlight Health Media, which publishes Highlight HEALTH, and lead writer at Highlight HEALTH.