The effects of chronic tea intake on platelet activation and inflammation: A double-blind placebo controlled trial

Background: Tea drinking appears to protect against the development of coronary heart disease (CHD), but the mediating pathways are uncertain. We studied the effects of 6 weeks of black tea or placebo on platelet activation, C-reactive protein (CRP), total antioxidant status, and soluble (s) P-Selectin in a randomized double-blind trial. Methods: Healthy non-smoking men aged 18-55 years were randomized to black tea (N = 37) or placebo (N = 38) following a 4-week washout period during which they drank no tea, coffee or caffeinated beverages, but consumed caffeinated placebo tea. Bloods were drawn after 6 weeks of treatment. Platelet activation was assessed by measuring leukocyte-platelet aggregates using whole blood flow cytometry. Results: Following treatment, the tea group had fewer monocyte-platelet aggregates (means 5.84 versus 6.60%, P = 0.027), neutrophil-platelet aggregates (P = 0.017), total leukocyte-platelet aggregates (P = 0.027), and lower plasma C-reactive protein (means 0.76 versus 0.97 mg/L, P = 0.05) than the placebo group. There were no differences in total antioxidant status or soluble P-Selectin. Conclusions: Chronic tea consumption reduces platelet activation and plasma C-reactive protein in healthy men. Effects cannot be attributed to observer bias or lifestyle confounders. These effects of tea may contribute to sustained cardiovascular health.