Green Tea Prevents Cold and Flu Symptoms

Green tea, from Camellia sinensis, is one of the world’s most popular drinks. It is a source of compounds called catechins that have been studied for weight control, cognitive focus, mental well-being, and cancer prevention. It turns out that these compounds may also prevent cold and flu symptoms.

In this clinical study, healthy adults took a green tea supplement twice a day for three months. In the supplement group, 32 percent fewer individuals experienced symptoms, and 22 percent fewer individuals who had an illness of two days or longer. Even among those who did get ill, 35 percent still had fewer symptom days overall.

The researchers discovered that one of the ways green tea worked was by increasing gamma-delta T-cell antigens to deal with immune threats. Gamma-delta T-cells are relatively rare immune defenders in the body, but they are absolutely necessary to deal with bacterial or viral infections.

One way to ensure even greater benefits from polyphenols is to consider a supplemental form that also includes grape seed, curcumin from turmeric, and other beneficial nutrients. Not only can green tea and additional natural ingredients help bolster your immune response, they can help protect cells from overall oxidative damage and inflammatory stress as well.


Rowe CA, Nantz MP, Bukowski JF, Percival SS. Specific formulation of Camellia sinensis prevents cold and flu symptoms and enhances gamma, delta T cell function: a randomized, double-blind, placebo-controlled study. J Am Coll Nutr. 2007 Oct;26(5):445-52.

Objective: Determine if a specific formulation of Camellia sinensis (CSF) can prevent illness and symptoms due to cold and flu, and enhance gammadelta T cell function

Design: Randomized, double-blind, placebo-controlled study.

Subjects: Healthy adults 18-70 years old.

Intervention: Proprietary formulation of Camellia sinensis (green tea) capsules, or a placebo, twice a day, for 3 months.

Measures of outcome: As assessed by daily symptom logs, percentage of subjects experiencing cold and flu symptoms, number of days subjects experienced symptoms, and percentage of subjects seeking medical treatment. Mean in vivo and ex vivo proliferative and interferon gamma responses of subjects’ peripheral blood mononuclear cells to gammadelta T cell antigen stimulation.

Results: Among subjects taking CSF there were 32.1% fewer subjects with symptoms (P = 0.035), 22.9% fewer overall illnesses of at least 2 days duration (P = 0.092), and 35.6% fewer symptom days (P < 0.002), compared to subjects taking placebo. gammadelta T cells from subjects taking CSF proliferated 28% more (P = 0.017) and secreted 26% more IFN-gamma (P = 0.046) in response to gammadelta T cell antigens, as compared to gammadelta T cells from subjects taking placebo. CSF was well-tolerated.

Conclusions: This proprietary formulation of CSF is a safe and effective dietary supplement for preventing cold and flu symptoms, and for enhancing gammadelta T cell function.