Specific formulation of Camellia sinensis prevents cold and flu symptoms and enhances gamma,delta T cell function: a randomized, double-blind, placebo-controlled study

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 METHODS: 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.