Effect of green tea on postprandial antioxidant capacity, serum lipids, C-reactive protein and glucose levels in patients with coronary artery disease

PURPOSE: Cardiovascular risk factors have been identified in the postprandial state, particularly in patients with coronary artery disease (CAD). Tea consumption has been linked to cardiovascular risk reduction, but the beneficial effect of tea has not been investigated under postprandial conditions. The objective was to examine the effect of green tea on postprandial levels of plasma total antioxidant capacity (TAC), serum lipids, C-reactive protein (CRP) and glucose in patients with CAD. METHODS: In a randomized controlled, parallel design with 2 arms, 43 patients with CAD were assigned to consume breakfast consisting of bread, butter and 330 ml water or tea (4.5 g green tea/330 ml, providing approximately 400 mg catechins). Blood samples were drawn immediately before and 1.5, 3 and 5 h after breakfast. TAC was measured in plasma with the ferric reducing antioxidant power of plasma and oxygen radical absorbance capacity assays. Total cholesterol, high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), triglycerides, glucose, CRP, uric acid and pancreatic lipase levels were measured in serum. RESULTS: Tested biomarkers did not differ between tea and water group at baseline, 1.5, 3 and 5 h (P > 0.05) postprandially. However, TAC increased 1.5 and 3 h after consumption of breakfast with tea (P < 0.005), but no change was observed after consumption of breakfast with water. Serum triglycerides levels significantly increased 3 h after breakfast with water (P = 0.031), but not after breakfast with tea. Serum uric acid decreased 1.5 h after breakfast with tea (P = 0.038). Pancreatic lipase, CRP, total cholesterol, HDL-C, LDL-C and glucose levels remained unchanged after breakfast with tea at any time point (P > 0.05). CONCLUSIONS: Tea consumption did not affect selected biomarkers at any postprandial time point in patients with CAD.