ABSTRACT
BACKGROUND: This study was undertaken to evaluate the possible effects of different daily doses of black tea intake on certain oxidative stress, inflammatory and metabolic biomarkers in patients with type 2 diabetes mellitus (T2DM). METHODS: Forty-six patients with known T2DM were randomly assigned either to the test (n = 23, 57.0 +/- 7.9 years) or the control (n = 23, 55.4 +/- 8.3 years) group. Following a one-week 'run-in' period, the test group received 150, 300, 450 and 600 ml of black tea extract (BTE) during the weeks 1, 2, 3 and 4, respectively. The control group received 150 ml BTE a day throughout the intervention period. Dietary, anthropometric and biochemical assessments were performed at the end of each week. FINDINGS: Serum total antioxidant capacity was enhanced similarly in both test and control groups. However, daily intake of 2 cups of BTE by the test group showed a suppressing effect on serum malondialdehyde. Serum C-reactive protein significantly decreased and glutathione levels increased following the intake of 4 cups (600 ml) of BTE a day. CONCLUSION: Regular intake of BTE had anti-oxidative and anti-inflammatory effects in patients with T2DM. These findings may, to some extent, explain the mechanisms underlying the protective effects of drinking tea against cardiovascular disease.