title: Acute effect of black and green tea on aortic stiffness and wave reflections.
abstract: OBJECTIVE
  While most studies have shown an inverse relation between tea consumption and cardiovascular risk, other studies have shown opposite results. Aortic stiffness and wave reflections are markers of cardiovascular disease and prognosticators of cardiovascular risk.
  
  
  METHODS
  The acute effect of black and green tea on aortic stiffness and wave reflections was assessed in 29 healthy volunteers in a randomized, single-blind, sham-procedure controlled, cross-over design. In the black tea sub-study, 16 subjects received 6 gm of tea, caffeine (175 mg), or hot water in 3 different sessions. In the green tea sub-study, 13 subjects received 6 gm of tea, caffeine (125 mg), or hot water. Carotid-femoral pulse wave velocity and wave reflection indices were measured at baseline and for 3 hours after consumption.
  
  
  RESULTS
  Black tea increased pulse wave velocity during the first 90 min (increase by 0.49 m/sec, P < 0.05), showing a rapid return towards baseline values thereafter (P = 0.07 for the whole study period); in contrast, green tea had no effect. Both black and green tea increased augmentation index (by 5.0% and by 6.6%, P < 0.01 and P < 0.001, respectively) throughout the study. These changes were less than the respective changes produced by caffeine. Both black and green tea had a significant pressor effect. No change in oxidant status was found with both types of tea.
  
  
  CONCLUSIONS
  Both black and green tea increases acutely wave reflections and only black tea increases aortic stiffness. Tea flavonoids may play a role in the attenuation of the effects of caffeine contained in tea.
authors.affiliation: Ist Department of Cardiology, Athens Medical School, Hippokration Hospital, Athens, Greece. cvlachop@otenet.gr
authors.forename: Charalambos
authors.initials: C
authors.lastname: Vlachopoulos
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Alexopoulos
authors.forename: Ioanna
authors.initials: I
authors.lastname: Dima
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Aznaouridis
authors.forename: Ioanna
authors.initials: I
authors.lastname: Andreadou
authors.forename: Christodoulos
authors.initials: C
authors.lastname: Stefanadis
mesh_terms: D000328:Adult; D001011:Aorta / Q000187:drug effects* / Q000502:physiology; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D002110:Caffeine / Q000009:adverse effects* / Q000494:pharmacology; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000209:etiology; D000697:Central Nervous System Stimulants / Q000009:adverse effects* / Q000494:pharmacology; D018592:Cross-Over Studies; D004548:Elasticity; D005260:Female; D005419:Flavonoids; D006801:Humans; D008297:Male; D011673:Pulsatile Flow / Q000187:drug effects* / Q000502:physiology*; D016037:Single-Blind Method; D013662:Tea / Q000737:chemistry; D013997:Time Factors
chemical_list: D000697:Central Nervous System Stimulants; D005419:Flavonoids; D013662:Tea; D002110:Caffeine