title: Effects of regular ingestion of black tea on haemostasis and cell adhesion molecules in humans.
abstract: OBJECTIVE
  To assess the effects in humans of regular ingestion of black tea on haemostasis-related variables and cell adhesion molecules.
  
  
  METHODS
  Twenty-two subjects were recruited from the general population to a randomised-controlled crossover study. Subjects stopped drinking tea, apart from that provided, for the duration of the study. During a 4-week baseline period all subjects drank 5 cups/day (250 ml) of hot water. The effects of 5 cups/day of black tea for 4 weeks were then compared with hot water. Platelet aggregation in response to three doses of collagen and ADP, plasma concentrations of coagulation and fibrinolytic factors (fibrinogen, factor VII, tPA, PAI-1) and plasma concentrations of cell adhesion molecules (soluble P-selectin, E-selectin, ICAM-1, VCAM-1) were assessed twice, one week apart, at the end of each period. Twenty-four hour urinary concentration of 4-O-methylgallic acid (4OMGA), assessed once at the end of each period, was used as a marker of black tea polyphenol intake.
  
  
  RESULTS
  The 24 h urinary excretion of 4OMGA was increased during regular ingestion of black tea in comparison to hot water (P<0.0001). Black tea resulted in lower soluble P-selectin (P=0.01) in comparison to hot water, but did not influence other adhesion molecules. Soluble P-selectin was significantly correlated with mean collagen-stimulated platelet aggregation at baseline (r=0.61, P=0.003), and during regular ingestion of hot water (r=0.70, P<0.0001) and black tea (r=0.51, P=0.01). However, platelet aggregation was not different between the black tea and hot water periods for collagen- or ADP-stimulated aggregation at any dose. Coagulation and fibrinolytic factors were also not different between periods.
  
  
  CONCLUSIONS
  The effect of black tea on soluble P-selectin provides a potential mechanism for cardiovascular benefits of regular ingestion of tea.
  
  
  BACKGROUND
  This study was supported by grants from the Tea Trade Health Research Association and the National Heart Foundation of Australia.
authors.affiliation: University of Western Australia Department of Medicine and HeartSearch, Royal Perth Hospital, Perth, Western Australia, Australia. jonathan@cyllene.uwa.edu.au
authors.forename: J M
authors.initials: JM
authors.lastname: Hodgson
authors.forename: I B
authors.initials: IB
authors.lastname: Puddey
authors.forename: T A
authors.initials: TA
authors.lastname: Mori
authors.forename: V
authors.initials: V
authors.lastname: Burke
authors.forename: R I
authors.initials: RI
authors.lastname: Baker
authors.forename: L J
authors.initials: LJ
authors.lastname: Beilin
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers; D015815:Cell Adhesion Molecules / Q000097:blood*; D018592:Cross-Over Studies; D005260:Female; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000652:urine*; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019007:P-Selectin / Q000097:blood* / Q000187:drug effects; D010974:Platelet Aggregation / Q000502:physiology; D013662:Tea
chemical_list: D015415:Biomarkers; D015815:Cell Adhesion Molecules; D019007:P-Selectin; D013662:Tea; C024272:3,5-dihydroxy-4-methoxybenzoic acid; D005707:Gallic Acid