Consumption of cranberry polyphenols enhances human gamma delta -T cell proliferation and reduces the number of symptoms associated with colds and influenza: a randomized, placebo-controlled intervention study

Background: Our main objective was to evaluate the ability of cranberry phytochemicals to modify immunity, specifically gamma delta -T cell proliferation, after daily consumption of a cranberry beverage, and its effect on health outcomes related to cold and influenza symptoms. Methods: The study was a randomized, double-blind, placebo-controlled, parallel intervention. Subjects drank a low calorie cranberry beverage (450 ml) made with a juice-derived, powdered cranberry fraction (n = 22) or a placebo beverage (n = 23), daily, for 10 wk. PBMC were cultured for six days with autologous serum and PHA-L stimulation. Cold and influenza symptoms were self-reported. Results: The proliferation index of gamma delta -T cells in culture was almost five times higher after 10 wk of cranberry beverage consumption (p