Researchers find a specific combination of green tea compounds reduce the incidence and duration of cold and flu symptoms

January 4, 2008

Fewer cold and flu symptoms are reported by otherwise healthy people who tried specific blend of compounds for three months

This cold and flu season, while those around you are coughing, sneezing and feeling miserable, you might be able to avoid getting sick altogether or at least reduce the number of days you experience symptoms by an average of 36 percent.

A clinical trial completed by researchers at University of Florida and the Nutritional Science Research Institute on a product called Immune Guard, has now clinically proven that a specific combination of ingredients, including the amino acid L-theanine (Suntheanine) and decaffeinated green tea catechins, including epigallocatechin gallate (EGCg; Sunphenon) can enhance the body’s immune system, resulting in a decreased incidence and duration of cold and flu symptoms. The findings appear in the October 2007 issue of the peer-reviewed Journal of the American College of Nutrition.

The lead investigators were Susan S. Percival, PhD, Professor of Nutritional Sciences in the Department of Food Science and Human Nutrition at University of Florida, and Jack F. Bukowski, MD, PhD, Chief Scientific Officer for the Nutritional Science Research Institute* and Assistant Clinical Professor of Medicine at Harvard Medical School. The randomized, double-blind, placebo-controlled trial, conducted at the University of Florida, followed 120 healthy people for three months. When compared to a placebo, the results showed that Immune Guard, a patent-pending blend of decaffeinated compounds from green tea (Camellia sinensis):

  • Decreased the number of people having cold and flu symptoms by 32 percent.
  • Decreased the number of symptom days by 36 percent.
  • Decreased the need for medical treatment due to cold and flu symptoms by 58 percent.
  • Enhanced innate immune function by 28 percent.

“Tea has been linked to good health for centuries. Not surprisingly however, it is complicated to study the benefits of green tea because of the hundreds of varieties, and the numerous ways to process, store and brew a cup of tea. There is also no general agreement on what quantity constitutes a single cup of tea,” said Dr. Percival.
“With this study, we were able to show that ingestion of a specific combination of decaffeinated tea polyphenols standardized to 45 percent EGCg and L-theanine, would enhance systemic immunity, and prevent cold and flu symptoms in healthy individuals. This is a significant finding.”

She added that, “Only about 20 percent of Americans drink any tea. Those who do only average one to two cups a day. Unfortunately, most health benefits from tea are associated with higher amounts of daily consumption. You would have to drink 10 cups of green tea daily to get a result similar to that which was found in this study, and that’s a lot of tea and a lot of caffeine.”

Dr. Bukowski, who is also an Associate Physician in the Department of Rheumatology, Immunology and Allergy at Brigham and Women’s Hospital in Boston, said, “Most green tea extracts are caffeinated, and no currently available tea extract has nearly enough L-theanine, polyphenols, and EGCg, which are necessary in correct combination and dose to realize their beneficial effect, while Immune Guard does.”

Meet the Experts

  • Derek Timm, PhD, RDN

    Derek Timm, PhD, RDN is more than your typical nutrition expert. In addition to being a registered dietitian nutritionist, Timm has earned a PhD in nutrition science. He is also a Monash University FODMAP-trained dietitian with expertise in how a high FODMAP diet impacts the symptoms of IBS.


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