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 (CHID), 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. (c) 2006 Elsevier Ireland Ltd. All rights reserved.