Black Tea Benefits Possibly Not Due to Catechins
Researchers have investigated the effects of black tea consumption on plasma catechins and markers of oxidative stress and inflammation in patients with coronary artery disease.
According to published research from the U.S., "We previously demonstrated that black tea consumption reverses endothelial dysfunction in patients with coronary artery disease. To investigate potential mechanisms of this effect, we examined plasma catechins and systemic markers of oxidation, inflammation, and antioxidant protection from 66 subjects enrolled in that study."
M.E. Widlansky and colleagues of Boston University explained, "We collected samples at baseline, two hours after 450ml of black tea (acute), after four weeks of 900ml of black tea per day (chronic), and after acute and chronic consumption of water."
"Total catechins increased 33% after acute tea (P<0.05) and 29% after chronic tea (P<0.05). Of individual catechins, plasma epicatechin gallate (ECG) concentration significantly increased with acute tea consumption, and plasma epicatechin (EC) increased with chronic tea consumption. Tea consumption did not improve plasma antioxidant capacity and did not reduce urinary 8-hydroxy-2'-deoxyguanosine, or urinary 8-isoprostane levels," the researchers reported.
"Changes in catechin levels did not correlate with changes in endothelial function, plasma markers of oxidative stress, or C-reactive protein. In contrast, endothelial function at baseline correlated with dietary flavonoid intake (beta=0.32, P=0.02) and with baseline plasma EC concentration after adjusting for confounding variables (beta=0.39, P=0.03)," they noted.
The authors concluded, "These findings suggest that the benefits of black tea consumption on endothelial function may not be attributable to tea catechins or a systemic antioxidant or anti-inflammatory effect. Chronic dietary flavonoid status appears to relate to endothelial function, possibly suggesting that other flavonoids or polyphenolic components of tea favorably influence vascular health and risk for cardiovascular disease."
Widlansky and colleagues published their findings in Free Radical Biology and Medicine ("Effects of Black Tea Consumption on Plasma Catechins and Markers of Oxidative Stress and Inflammation in Patients with Coronary Artery Disease." Free Radic Biol Med, 2005;38(4):499-506).
Additional information can be obtained by contacting J.A. Vita, Boston University Medical Center, School of Medicine, Evans Department of Medicine, Cardiology Section, 88 E. Newton Street, Boston, MA 02118.